RICHARD SOLOSKI, Magnolia

A. First of all, do not polyurethane the brick; brick should be left bare. Or, you could seal the brick with a clear sealer. For your purposes, dig down deeply enough to put in 6 inches of crushed stone, then 2 inches of stone dust as a bed for the brick. Tamp it down as compactly as you can, smooth it out, then set the bricks very close together, so they are touching.

If you plan to use the brick as a heat sink (letting the bricks warm up from the sun so that they will release their heat when the sun goes down), you have to put 2-to-4 inches of styrofoam insulation under the crushed stone; otherwise the bricks will conduct the sun's heat into the ground instead of retaining it for release when the sun goes down.

Actually, it's a good idea to put the insulation under the crushed stone anyway, in case you ever want to convert the room into heated living space.

Q. I poured 3 inches of concrete over my concrete basement floor, which was full of cracks. The new floor has developed cracks that line up with the old ones. I plan to use the cellar as an animal shelter, so the floor has to be waterproof. What next?

D.R., Halifax

A. Concrete is great stuff -- in compression; that is, it can take great weights pressing down on it. But it is poor in tension (forces pressing against its length). So, when you poured the new floor, it followed the contours of the old floor, and since the old floor was cracked because of unevenness in the substructure, the new layer did exactly the same thing. Even if you put in reinforcing bars or mesh, it could have happened the same way.

Normally this would not be harmful but to make it waterproof for use as an animal shelter something else must be done. You have these choices:

- Put down wire-mesh reinforcing secured to the new concrete, then add an inch or so of mortar. After that sets, put down ceramic tiles with thin-set mortar. A good mason can make that mortar layer smooth, level, and even, so you could use large (12-inch square) tiles. If the mortar bed is not that even, then use smaller tiles, which would be less likely to crack from tension.

- Remove the 3 inches of new concrete, secure the wire mesh to the old surface, then mortar and tile as above.

- Remove all the concrete and lay a new slab, with reinforcing bars or mesh.

Q. I am having my hardwood floors refinished. The refinisher said he specializes in moisture-cured polyurethane. Is it good?

SHEILA STEMPECK, Reading

A. Is it good? I think it is the best onsite finish you can get. Jim Richards, who heads up Marco Products of Marblehead, says his product (ASTM Type II moisture-cured aliphatic polyurethane) is the best. It is rarely if every applied by the do-it-yourselfer because it is very toxic and unhealthy to be around as it cures. Because of its toxicity, it is suggested the homeowner leave the house for a few days while the material is installed.

Q. My 1880s house has wall-to-wall carpeting, and my daughter wants to have a wood floor, which is under the carpeting. Taking off the carpeting was easy, but there are gaps between the wood floor boards. How can I fill those gaps?

A.D., Newton

A. Well, it depends. If the boards are square-edged (and they might be, considering the age of the house), you can cut thin strips of similar wood and insert them in the gaps. If each gap varies in width, then you have to trim the filler strips to fit. If you do this, be sure to stain the strips slightly darker then the original floor so they will not stand out. Or, stuff hemp rope in the gaps; depending on the depth of the gaps, you may have to use two layers, and you can stain hemp as well. And, the rope will fill uneven gaps very nicely.

Don't try to fill the gaps with wood filler that hardens as it sets; it looks good for a few weeks, or months, maybe, but when the boards start to expand and contract from moisture content, the filler will break up and look worse than open gaps.

If the boards are tongue-and-groove, the gaps are very shallow (less than a quarter-inch), and you cannot insert wood strips or anything else.

The cure for gaps in tongue-and-groove boards is to take them up in winter (when the boards are driest and smallest), and re-lay them tight in the same order they were in the first place. You can do this with square-edged boards as well. Sounds difficult, but, while not easy, it is an effective cure. The Handyman did this with wide pine boards in four rooms 25 years ago, and they are still tight.

Q. In renovating our house, we put in a new oak floor in the entry and a sunroom that we opened up to the living room. We sanded the old floors and had them finished, but we noticed that the old floor, sanded and finished, is considerably darker than the new floor, which is also sanded and finished. I think they used white oak for the new floor while the old floor is red oak. How can we get a match?

J.M., Arlington

A. A hard assignment, I think, but what you can do at the entry is to put in an oak threshold where the two floors meet. This will delineate the space and make the difference in color easier to take.

But a threshold will not work for the sunroom because, as you said, it is part of the living room now. Understood. So, for the sunroom, your only choice is to sand the floors of that room and apply a stain of your choice to try to match the old floor, then finish. One thing you cannot fix is the contrast in the grain of the oak in each floor; the difference is almost as distinct as the color difference. But once you get a color match, this grain difference might be tolerable.

Another thought: Cover the border where the two floors meet with an area rug.

Q. I plan to put ceramic tiles on my bathroom floor. The house is nearly 70 years old. There is vinyl flooring there now, and I was told that under that vinyl is asbestos. What can I do now before putting in the ceramic tile?

BILL GENTLE, Arlington

A. You won't know what is under the vinyl until you test both the vinyl that's on the floor now and anything underneath. Sheet vinyl, installed as recently as 15 to 20 years ago, may have a white or gray backing; if so, it is probably asbestos. Break off a small piece and have it tested by an asbestos abatement company (in the Yellow Pages). If there is no asbestos, you can go ahead and scrape up everything to the wood floor. Then put down a sheet of concrete board (WonderBoard is one brand), and apply the tiles with a thin-set mortar. You could do the same over the existing sheet vinyl.

Q. I like the idea you suggested to stain the basement concrete floor with a concrete stain, but then you said that Benjamin Moore no longer makes one. Does anyone?

A.B., Belmont

A. Let's hear it for Muralo, a manufacturer that makes a concrete stain, and in considerably more colors than did Moore, which stopped its production because of environmental concerns and taboos. Let's hope that Muralo doesn't run into them, too.

I discovered the Muralo stain at Factory Paint Store, where I went not only to pick up some paint but also to ``case'' the place to see what was new and different and exciting.

The reason I like the idea of a stain for concrete is that it is unlikely to peel, perhaps not peel at all, which is one of the problems with paint on a concrete floor. Paint will peel, no matter what you do, and it is a big pain to scrape it off and do it all over again. With stain, since it resists peeling, you can wait until it fades or wears off, then repeat, without scraping. Of course, stain can go only over bare concrete.

And, if Muralo discontinues its concrete stain for any reason, you can always use an ordinary oil-based semitransparent house stain, which comes in many earth colors. While it is not designed for floors, it will work, applied thinly.

Q. Should I finish it with water-based polyurethane varnish or oil-based?

ED FARR, Newton Centre

A. Oil-based, by all means, if you are going to do it yourself. Three coats will do well. If you are having it done professionally, I suggest the installers use a moisture-cured polyurethane.

Or, buy prefinished boards, and specify that they have three or four coats, factory applied. These boards are a little more expensive than the bare wood, but they don't have to be sanded and varnished.

When Fran Olfe of Brookline asked how to maintain newly polyurethaned floors, and especially how to handle scuff marks, the handyman suggested dry mopping and vacuuming, with a bit of damp mopping for stubborn spots. And for the scuff marks, light rubbing with a soap pad or steel wool and oil.

That's OK as far as it went, but Eileen Padua of Dorchester wrote to share her method, adding, ``I think this is the third time I've told you this over the years.

``Mop and Glo in the blue bottle used sparingly with a damp mop or cloth will clean scuff marks and make minor scratches disappear. I do it once every couple of months and have never had any buildup,'' she said.

``I have had polyurethaned wood floors 25 years old that have had no other treatment. I also use Mop and Glo on floors I had sanded and polyurethaned last year.''

Thank you, Eileen Padua, for the third time. Now your tip is in the handyman's handy-dandy file for future reference.

Q. My Cape Cod-style house has storage space behind the upstairs knee walls, the low walls that go from floor to sloping ceiling. The walls and the floor are insulated. How thick should the floor insulation be?

M.B.M., Quincy

A. For all practical purposes, as thick as the floor joists are. They are probably 2-by-8s or 2-by-10s. If the insulation does not reach the top of the joists, add enough to do so: Fiberglass batts or rolls, or pouring insulation will do. Do not put insulation in the overhang, where it could block any soffit vents there now or in the future. Even without soffit vents, the eaves are venting a bit, and should not be filled with insulation.

Q. I spilled fingernail polish on my marble bath floor. How can I remove it? The polish is clear and does not show much, but I'd still like to remove it.

K.C., Boston

A. Try acetone, or fingernail polish remover. Try it in an obscure corner to make sure it does not etch the marble. If it does, you could try a little light sanding with very fine sandpaper to hit the polish and not the marble.

Q. I plan to put a Pergo floor, the laminated plastic, in my kitchen, but I am concerned as to what the table and chairs will do to it, such as scratching. And, is a Pergo floor too slippery when wet?

CHARLIE, from Norwood

A. While the Pergo is guaranteed for 15 years (not long for a floor), any floor surface except a rug will be scratched, or at least is likely to be scratched by a moving chair, especially if one tiny grain of sand gets between leg and floor. And that goes for Pergo, varnished wood, linoleum, sheet vinyl, resilient tile, and ceramic tile. Of course, some, such as glazed tile, are more resistant to scratching than others. But there is hope: Put a glide at the ends of the table and chair legs. Felt tips work well but wear out quickly, but better are nylon glides that can be nailed into the ends of legs. A more permanent cure is to put area rugs under tables and chairs. Simple, but logical. As for slipperiness, any smooth, hard, shiny surface is slippery when wet, but Pergo is not necessarily slipperier than any other surface. It is a matter of staying off a newly-washed floor until it dries, and to wipe up liquid spills quickly (any spills, really) before someone trips, slips and falls.

Q. My 1880s house has wall-to-wall carpeting, and my daughter wants to have a wood floor, which is under the carpeting. Taking off the carpeting was easy, but there are gaps between the wood floor boards. How can I fill those gaps?

A.D., Newton

A. Well, it depends. If the boards are square-edged (and they might be, considering the age of the house), you can cut thin strips of similar wood and insert them in the gaps. If each gap varies in width, then you have to trim the filler strips to fit. If you do this, be sure to stain the strips slightly darker then the original floor so they will not stand out. Or, stuff hemp rope in the gaps; depending on the depth of the gaps, you may have to use two layers, and you can stain hemp as well. And, the rope will fill uneven gaps very nicely. Don't try to fill the gaps with wood filler that hardens as it sets; it looks good for a few weeks, or months, maybe, but when the boards start to expand and contract from moisture content, the filler will break up and look worse than open gaps. If the boards are tongue-and-groove, the gaps are very shallow (less than a quarter-inch), and you cannot insert wood strips or anything else. The cure for gaps in tongue-and-groove boards is to take them up in winter (when the boards are driest and smallest), and re-lay them tight in the same order they were in the first place. You can do this with square-edged boards as well. Sounds difficult but, while it is not easy, it is an effective cure. The Handyman did this with wide pine boards in four rooms 25 years ago and they are still tight.

Q. As the father of triplets, I found my family doubled in size, and it was a case of instant outgrowing of my 48-foot-long, ranch-style house. I like the area and was thinking of moving up, not out; that is, adding a second floor. To do this, do I need an architect or a builder? Wouldn't an architect be expensive? Whom should I consult?

R.P., Ipswich

A. You wouldn't necessarily need an architect, but also an architect's fees may surprise you. Most contractors can design a project according to your description. Or, find an architect-builder, one that not only designs but does the work as well. Also, consider hiring a contractor who will raise the roof in order to add the second story rather than removing it.

Generally, a critical part of adding a second story to a one-story house is the floor joists; in some ranch houses, the joists were designed to hold up a ceiling, not a floor, so they might have been undersized. In that case, bigger joists must be added.

Q. I bought a Federal house in 1992, when the house inspector told me that the second floor has a spring in it; it bounces when it is walked on. It is still bad, so bad that even tiptoeing across the bedroom causes the handles on the bureaus to wiggle and rattle. How can I stiffen that floor? The span of the joists is 16 feet.

BILL HART, Newburyport

A. It is obvious that the joists are too small for that 16-foot span. And being an old house (the Federal period was around the turn of the 19th century), the joists may be dinky little 4 x 6s, way too small for that span. Presumably they are not decaying from moisture or any other cause.

You could sister larger joists to those undersize joists; sistering is simply nailing the new joists on the side of the old and making sure the new ones are also supported at each end. This requires removing the ceiling, and if the new joists are deeper than the old, the new ceiling will be lower.

The only other way to do it is to set a large beam, perhaps a 6 x 12, under the joists right down their middle, at right angles to them and supported at each end by posts. This will shorten the span by half and stop the spring. And a good thing about this center-beam system is that you don't have to take down the ceiling.

Dorothy McCown of Aledo, Ill., is 82 years young this month and is always doing things with her house. She took the time to write to the handyman that she solved a problem of some adhesive that got smeared on the top of new vinyl tiles laid on the bathroom floor. Worse, the adhesive had been drying for several days when she discovered it.

She took it off with Soft Scrub ``with no effort and no damage to the vinyl. I use Soft Scrub for many things: my counter tops, the white enamel stove, and other areas. With Soft Scrub there is no waiting.''

Thank you, Dorothy McCown. Soft Scrub is quite amazing. It is slightly abrasive (but not as abrasive as Ajax and other cleansers) and is good for cleaning soap scum off any surface, as well as for cleaning fiberglass, ceramic tiles, Corian, and almost anything else. And, as Dorothy says, without damage.

Q. Is it practical to install ceramic tile on a breezeway floor made of doubled plywood?

MARGUERITE PALUMBO, Woburn

A. Yes, as long as there is ventilation under the doubled plywood floor, which will be more than strong enough to hold a ceramic floor and lots of other things, too. Use thin-set mortar just a tad thicker than normally, so yu can fill in low spots and smooth off any unevenness.

Q. I plan to take up the old sheet vinyl floor, and put down ceramic tile. The installer is screwing the plywood every 6 inches and will apply the tile with thin-set mortar. Originally I had the baseboard heaters removed and radiant heat put under the floor. My question is: Does the tile go on first, then the baseboard, or vice versa?

J.O., Norfolk

A. A short answer to a long question: Either way is acceptable. I think it's best to put the baseboard in second, on top of the tile. This way you will have a horizontal joint, which will collect less dirt than a vertical joint, and you can caulk it if you like. If the baseboard is put on first and tile butted against it, the joint should be large enough (one-eighth inch will do) to hold grout, and this grout may break up quickly because it connects ceramic with wood; wood will expand and contract with moisture content, whereas the tile will not.

Q. The plywood floor of my out building is rotting out after only 5 1/2 years. I put 4 x 4 pressure-treated sleepers on crushed stone, back-painted the plywood (on all faces and edges), put sheet polyethylene on top of the sleepers, then the plywood, then vinyl tiles. Just the plywood is decaying. What's wrong and how can I fix it?

SARKIS TOOMAJIAN, Winchester

A. The sheet polyethylene under the plywood and the unventilated space between the sleepers (covered at both ends) are the culprits. Instead of keeping moisture out, that poly is trapping moisture in the plywood. So, replace the plywood with pressure-treated plywood and do not put any thing under it except the existing timbers. And, drill holes in those perimeter sleepers for cross-ventilation. Or, put in pressure-treated, spaced boards as a floor.

Q. I am sanding a hardwood floor after removing a linoleum cover, but discovered a lot of nail holes. How can I fill them before I sand, and how can I disguise them?

ARTHUR CARILO, Worcester

A. Fill the holes with wood filler. It is a beige color and may show a little but there is nothing more you can do to disguise them. Then when you sand the floor you will also sand any wood filler that got smeared on the wood. Finish with three coats of an oil-based polyurethane varnish. You will not notice the filled holes unless you look for them.

Q. When I built a house on Martha's Vineyard, a random-width red oak floor was installed in mid-September. I was told it will be tight for 40 years, but now there are gaps between the boards; I can get a paper card through some, but others are as wide as 1/4 inch. I have a wood stove in that room. What went wrong and how can it be fixed?

PAT MESSENGER, The Vineyard

A. It's an old, sad story about gaps in hardwood floors. The boards were not quite dry enough when they were installed, and when winter came, they dried out and shrank, causing the gaps. There is nothing you can do about it except to pick up the boards and reinstall them now, when they are at their smallest. Since the house is in warranty (houses are usually warranted for a year) the builder should do it for free, with big smile. The wood stove probably had little to do with the shrinking and drying out of the boards; they will dry out in a house heated in any way.

One ray of hope, but of little comfort: In summer, when the boards take in moisture and expand, the gaps will close.

Here are a couple of fix-it ideas from Thelma Dame of Guilford, N.H., who called to give them to the handyman. The handyman is grateful for such ideas, and files them away in his newfangled electronic file. ``My windows are friction fit, and almost never stay up when they are supposed to,'' said Dame, ``so I put a stick under them. Easy, really. I also insulated the weight pockets. ``I discovered that Ultra-Brite toothpaste will help clean marble. One of my white marble commode tops was all smokey and dirty. I dropped the toothpaste on the top, and sure enough, it cleaned it with a little rubbing.''

Good idea, Thelma Dame. But if anyone wants to try it, do so on an obscure corner to make sure it doesn't make the marble worse. She's not through:

``When I get air leaks between my windows and storms, and get fogging, I put a half a cup of baking soda in the cavity. No more fogging. I did the same with a huge picture window with 96 panes with the same problem, and no more fogging. I had to take down a huge storm over the picture window, but it was worth it.'' There's nothing like a Dame. Thanks.

Q. My floor was polyurethaned. After 48 hours, little puddles of varnish remain, and they are not drying. What can be done?

JOHN EMENEY, Beverly

A. The varnish simply was put on too thickly. It will dry eventually. Provide a little ventilation (a fan set on the floor) to hasten the drying. If the polyurethane is water-based, it might turn cloudy. If it does, then the floor should be refinished, and the installer should do it, gratis.

Q. Six months after my house was completed four years ago, some of the floor joists started to rise, so the floor is off level. I also discovered that the joists were warped. What can I do about it? I contacted the builder about this right after it happened.

E. R., Oxford

A. The joists were green (full of water) when they were installed, and warped when they dried out.

Since you contacted the builder before a year was up, when the house was still in warranty, the builder is, or should be, responsible for repair. I think the joists should be replaced with straight, cured joists (those with a minimum of moisture).

That is one heck of a project but it can be done, and should be. A viable alternative might be to cut the tops of those warped joists so that the tops are level.

Then install a straight, cured joist next to each bad joist, then secure the floor to the new joists. It is called sistering and is a horrendous project, but it can work.

Q. One of the floors in my house on the Cape is quarry tile. How can I seal it so it won't collect so many stains?

J.R., Quincy

A. You are right about those stains; quarry tile, which is unglazed, will stain if you look at it. It is very absorbent, like marble, and is a pain to keep clean. You can seal it with a clear masonry or tile sealer, which will make it water-resistant and therefore resistant to stains, and easy to clean. But this sealer should be reapplied every two years or so.

Before you apply the sealer, try it in an obscure area; if the sealer causes white spots, it should not be used because there is already something on the tile. There is another type of sealer that you might try instead of the masonry sealer. Some people have had good luck in applying Future, the acrylic linoleum sealer. Again, try it in an obscure area to make sure it does not cause white spots. If either Future or the sealer causes white spots, there is something already on the tile, which would have to be removed if you want to seal it.

The only other alternative that I know of is to install glazed tile, which resists stains and is eminently washable.

Q. I refinished the wide Southern yellow pine floors in my house, and they look great, except for one thing: those darned wide gaps between the boards, 1/8 to 1/4 inch wide. What can I fill them with that will look good without breaking up and last awhile?

MICHELLE HALL, Wakefield

A. It's an old story, and it has been plaguing New Englanders for centuries. The gaps occur when the boards lose moisture and shrink. The boards expand when they gain moisture, and sometimes in the summer, when it is very humid, the boards will expand enough to close the gaps. Eventually, after repeated expanding and contracting of the boards, the gaps remain.

You could just leave them alone and live with them, but they tend to fill up with debris, which can get pretty repulsive. Another solution is to pick them up and relay them tight against each other. If you do this, be sure to do it in winter, when the boards are at their smallest. If you relay the boards in summer, when they are at their largest, the gaps would show up again when the boards shrink in winter.

As for filling the gaps, a putty that hardens will not work because it will just break up and look worse than ever. You could cut a thin strip of pine and insert it in the gap, but this is iffy, particularly if a gap varies in width. If you can make a wood strip work, stain it a little darker than the finished floor before inserting it. A slightly darker strip will look better than one that is lighter.

But here are two possibilities: Fill the gaps with a caulk colored the same or a little darker than the floor. Leave a slight depression in the gap so you will not walk on the caulk. The caulk will expand and contract as the crack grows or shrinks.

Finally, try this trick used by the Hitchcock Chair Co. in Connecticut on one of its buildings that had wide boards and big gaps. Buy hemp rope, real hemp, that is, which is a light-colored, very strandy material. Tuck it in the gap with a chisel (you may need two layers of rope). And, be sure to stain the rope before installing it.

Q. I am a first-time homeowner, with a two-family that is kind of wobbly. I live on the second and third floor, and my bed jiggles when someone climbs the stairs. Anything I can do? At least the floors are not sloping -- too much.

S.L., Somerville

A. The only time the handyman's bed jiggled was a few years ago on the top floor of a hotel in Osaka, Japan. Actually, the bed swayed rather than jiggled, and fortunately, it stopped before I had time to panic. It was an earthquake, only seconds long, thank goodness.

Someone climbing your stairs is a form of earthquake, or a least a housequake, with similar results. Your house is unlikely to fall down, but it is wobbly or jiggly because, generally, the joists (the horizontal beams holding up the floor) are too small for their span. You can't do much about the second and third floors without extensive work because they are not accessible, but you might be able to do something about the first floor.

Since this work is structural, you must employ an engineer or an architect, and have it done by a contractor. An engineer or architect also might find other reasons for the jiggling and wobbling.

This is generally how it is done if the joists are too small: Make sure the big center beam in the cellar, the one usually running down the middle of the basement ceiling, the full length of the house, is in good condition and properly supported by posts, at each of its ends. Check that the wood sills on top of the foundation also are in good condition. This determined, a cripple joist, larger than the existing one, is installed against each existing joist (called sister joists).

Another way it's done: A large beam is installed under and at right angles to the joists, right down the midpoint of the joists. This beam is supported with posts, reducing the joists' span by half. Either technique makes the whole floor more rigid, eliminating or reducing the jiggling. And since the first floor is made more rigid, the jiggling of the floors above may be reduced or eliminated. And since the stairway is a part of the floor, making the floor rigid will help reduce jiggling of the stairway, and your galloping bed.

When M.B. of Rockland burned a frozen scone in her microwave, creating an awful smell in the microwave and in the kitchen, the handyman suggested cleaning the microwave with baking soda to get rid of the odor. He also suggested using a deodorant called Natural Magic Odor Blaster, if the baking soda didn't work.

Susan Hernon of Cohasset called to give us a better way, or at least an easier way: ``I use white vinegar, and it eliminates many odors, including those in the microwave. Put white vinegar in a glass bowl and turn the microwave on for a while. Or, put the vinegar on the floor of the microwave and turn it on. It just washes away. I get rid of any remaining odor of vinegar by washing the inside of the microwave.''

Thanks, Susan Hernon, and your good idea goes right into the handyman's memory bank, where it should have been in the first place.

Q. The self-adhesive disks under my sofa feet, designed, of course, to keep the feet from scratching the floor, have failed, leaving black sticky stuff on the floor. The floors are not yet scratched, but how can I get that sticky stuff off? And what can I use to protect the floor without the same thing happening again?

GINA GROCCIA, Worcester

A. Try a little oil on the black spots; any kind will do. Let it sit on the spots for 15 minutes (to soften the black stuff), then wipe or scrape up the black. Be sure to wipe up all the oil and black, because most oils left on any surface will get sticky and stay that way. Also, dispose of the oily cloths safely by burning them; they can spontaneously ignite if left lying around. Other solvents that may work are paint thinner, rubbing alcohol and dry-cleaning fluid. None will hurt the floor.

To protect the floor from the sofa feet, buy rubber cups; they come in brown and white, will not disintegrate, and will not transfer anything to the floor. Another possibility is to buy nylon buttons; the type with a nail that you drive into the feet. The nylon allows the sofa to move (maybe too much) without scratching the floor. I have found that the rubber cups work best, and keep the sofa from sliding when it shouldn't. Your sofa may not be on a rug, but there is another kind of cup that will work nicely, if all or some of the feet are on a rug. These special cups have a bunch of short, stiff, plastic or rubber fingers at the bottom, which grip the rug nicely.

Q. I bought a townhouse with concrete slab floors. I had hardwood strip flooring glued down, but the glue failed. I propose to have plywood applied with nails and then the hardwood installed. Will this work, or is there a better way?

JEAN DRISCOLL, Braintree

A. The plywood nailed in, then the hardwood, should work well. There are two other ways, not necessarily better: 1. Install a floating hardwood floor -- strips that are fastened to one another but not to the concrete. This type of floor is designed to float on the concrete, so you don't have to worry about its sticking. 2. A Pergo floor, which is laminated plastic (it looks pretty good for fake hardwood) backed by a foam backing and glued on the concrete.

Q. I am putting a hardwood floor in the dining room. How can I cover the threshold at a doorway where the floor in one room will be about three-quarters of an inch higher than that in another?

STUART SALTZNIAN, Mansfield

A. If the threshold is marble, I suggest pulling it up and putting in a filler piece of marble or hardwood. Then put the threshold back down so it is sitting on the filler marble as well as the hardwood. Or, leave it in position and let the hardwood butt up against it. You can do the same with an oak threshold.

Q. Spilled stripper messed up a varnished floor. How can I restore those spots without sanding and finishing the entire floor?

KELLY RYAN, Cambridge

A. You can try spot-finishing, which will work, but the revarnished spots will be shinier than the original. Those shiny spots will, however, dull down in a few months. I spot-finished areas of a pine floor, and they were shinier than the original finish. Some time later, they had dulled down to match the original.

And here is how to do it: Wash the spots with paint thinner to neutralize the stripper. Sand the area lightly, enough to expose bare wood. Wash again with paint thinner. Apply two or three coats of an oil-based polyurethane varnish. I suggest oil-based because the original finish was probably oil-based. Water-based varnish might not be compatible with the original. Also, use a semigloss or satin varnish, which will contrast less with the original.

To apply, dip a clean cloth into the varnish and wipe it on the spot, with a firm but single wiping. Do not rewipe. Let dry and do it again. Thin coats are important, and have a better chance of blending in with the original finish.

If the spill area is large, you might try refinishing the entire length of the boards affected. That way, any contrast will be along boards that abut the undamaged boards, and will not show much if at all. And you won't be refinishing an area that goes across the boards, which would stick out like a sore thumb.

When Jerry Connolly of Newton asked how to remove individual wood shingles from his house wall, the handyman gave several techniques that would work. Special techniques are needed because the shingles are blind-nailed; that is, the nails in one row of shingles is covered by the next higher row.

You forgot one thing, said Jerry the Handyman of Dennis. ``Don't forget a shingle puller.''

Good point, Jerry. A shingle puller, originally called a slate puller, is an ingenious tool for cutting hidden nails that cannot be reached any other way. It consists of a flat steel bar with a double hook blade at one end, and a raised handle at the other. Slip this bar, hook forward, under the shingle and hook the blade over the hidden nail (you have to do this by feel), and whack the handle with a hammer. Presto, the nail is cut and the shingle can be pulled out.

One thing to be alert to: The wood shingles are nailed tightly against the sheathing, and it might take some tricky maneuvering to get the tool between the shingles.

Q. I had my hardwood floor cleaned and oiled two years ago. Now the floor is gummy, like honey. Did I do something wrong? How can I fix it? Fortunately, only one room is messed up.

C.P., Somerville

A. An oiled floor is hardly ever satisfactory; I would be surprised if it didn't become gummy shortly after it was oiled. With any oiled surface, the oil must be applied, then after 15 minutes, all oil must be wiped up with a dry cloth, or at least all oil as can come off must be removed; otherwise, it will stay sticky. Paint thinner might dissolve the oil enough so it can be wiped up with a dry cloth, even scraped. If this works, you don't have to go any further. You can leave the surface as is (there is still oil on it) or you can apply two coats of oil-based polyurethane varnish. It will provide a harder finish that can scratch, but it will look good and will be washable, or cleanable.

If the paint thinner does not remove the oil, try chemical paint remover. Use ventilation when using paint thinner or chemical paint remover.

If none of these treatments works, you will have to have the floor sanded and varnished. Forget about the oil.

There are no guarantees with any of these projects. If in doubt, you could try these treatments on a small, obscure area of the floor to see if something works or fails. And be sure to dispose of oily cloths safely by burning them.

Q. I am putting hardwood floors in my 12-year-old house. Which type should I use: solid oak or laminated? The plywood floors creak a lot. How can I quiet them?

S.S., Easton

A. Solid, by all means. Solid oak ( 5/8- to 3/4-inch thick) will last 100 years, given its ability to be sanded up to four times, once every 25 years. You're lucky if the laminated floor lasts 20.

Since the floors are plywood, you can locate the joists under that plywood; mark them with a pencil line and drive 3-inch galvanized deck screws through the plywood and into the joists. You probably have two layers of plywood; the extra-long screws will go through both layers into the joists. Even if there is only one layer, it won't hurt to use long screws. The new screws will bring the plywood layers together and secure them permanently to the joists. As of now, the plywood is loose, having dried out and shrunk, and moves when stepped on; the creaking is the sound of wood scraping against nails. Stop that movement and you stop the creaks.

Q. My wide pine board floors in a reproduction house are showing a bit of wear and tear. Will resanding hurt the floor? Or should I refinish the floors another way, without heavy sanding?

P.C., Groton

A. It's an old wives' tale that heavy sanding will damage a soft-wood floor. You can sand a pine floor as many times as practical, as many times as any hardwood floor.

You can refinish one of two ways. If the floor is not badly or deeply scratched, you can sand lightly, with fine sandpaper, mainly to roughen the finish and reduce gloss, not taking much of the wood off. Then apply three coats of high-gloss, oil-based polyurethane varnish. You could power sand with a belt sander or use the new square-plate floor sanders, available at rental stores. These new sanders are much easier on the floors and the operator than the old drum floor sanders.

The other way is to use a square-plate floor sander and sand three times, with coarse, medium and fine sandpaper; this is complete refinishing; then finish as above, with the three coats of polyurethane varnish.

The new square-plate sanders are excellent; they do a good job but are much gentler on the floor, and can be operated almost with one hand. The old drum sanders were powerful machines that ran so fast that the operator was hard put to keep from being pulled clear out of the house; they were also much harder to control and keep from gouging or rippling the floor than the plate sanders.

Q. The third and fourth floor on my condo are concrete. Can I put down a plank hardwood floor? I don't want to use any kind of new laminated plastic made to look like wood. So what can I use?

G.B., Boston

A. I think the best floor on concrete that is not on grade or below grade is a floating floor. It is laminated, and set down in one piece (the boards are nailed together in a unique fashion), and just sits there. You will get a double ``click'' when you walk on these floors because they are not secured to the concrete, but it's the nature of the technique.

You might also be able to install oak planks, by driving screws through the planks and into the concrete, but you may have to predrill holes in the concrete. If that is possible, countersink the screws and fill the resulting holes with wood dowels.

Q. My house is 30 years old. I am replacing wall-to-wall carpeting, and when I asked the company to fix the squeaks in the hardwood floor, the men said to do so they would have to pick up the boards and relay them. Is that necessary?

MATT LUZ, Natick

A. Well, that is one way of eliminating squeaks; in fact it is the best way, but not necessarily the only way. The basic technique to terminate squeaks is to bring the top floor (the hardwood) in contact with the subfloor boards or plywood, and to bring both in contact with the joists they are sitting on, so nothing will move when the floor is walked on. It's the movement of the floors, rubbing against nails, that is causing the squeaks.

If the floor is accessible from below, drive wedges (wood shingles are good wedges) between the subfloor and the joist. Another way is to buy a kit called Squeeeeek No More, sold in the Improvements catalog (phone 800-642-2112). It consists of a jig for driving 3-inch screws through the floor and into the joists, and 50 screws. The screw is then broken off below the floor surface. Screws must go into joists.

If the floor is going to be covered, you could drive screws directly through the floor into the joists, without countersinking them. This is not the best of treatments because a future owner of the house might not take too well to a floor with a bunch of screw heads showing.

Q. I painted part of my basement concrete floor. I washed the floor first, then applied an acrylic floor enamel. So far so good. I have not done all the floor or the garage, and was wondering if I did the right thing.

ALAN HAMWEY, Chelmsford

A. Well, maybe. If the paint you used stands up without peeling for a number of years, you did the right thing. You also did the right thing by not painting the rest of the basement floor and particularly the garage floor.

The problem with paint on a concrete floor is that water vapor that is coming up through the concrete is likely to push that paint right off. In the case of a garage floor, you not only have the water vapor problem but also the problem of the pressure, heat, and twisting that auto tires inflict on paint. I know of no paint that stands up to that.

Some epoxy paints work well for years. But I feel that the only way to treat a concrete floor (basement or garage) is with a concrete stain. Moore makes one, in seven colors plus white. These stains may show tire marks and footprints, but it will not peel. If you have ever spilled a semitransparent house stain on concrete, you know this is true because indoors it never seems to come off.

More about those brass bath fixtures. Last Sunday the handyman suggested to Phyllis Peach of Newton that her brass fixtures turned black because the lacquer finish was defective. The fixtures had been replaced once after they turned black, and the new ones turned black as well. The handyman indicated that replacement was probably the only cure.

However, Jock Castoldi, vice president of Thompson-Durkee Co. of Alston and North Plymouth, wrote that the finish was not necessarily defective. ``Yes, polished brass faucets are all the rage and when cared for properly will provide the homeowner a `lifetime' of satisfaction. Your statement that `the lacquering was defective,' is pure conjecture on your part. Blackening is more the result of improper care of the product. Faucet manufacturers recommend their products be cleaned with mild soap and water and nothing else.

``When a homeowner uses an ammonia base product such as Windex or some other aggressive chemical to clean their faucets with, you get a blackening result Phyllis Beach described. The blackening is symptomatic of using an aggressive cleaner, and will usually void any warranty provided with the product.''

Good point, Jock Castoldi, proving that proper care is essential to the success of most fixtures and other equipment around the house -- and noting that there are new brass finishes that are better than lacquered ones.

I guess I'm old fashioned, but I feel that chrome will perform better with less care, even abuse, than virtually any other finish.

Q. Would Pergo flooring be OK for a concrete floor?

GARY LIVOLSI, Boston

A. Yes. Pergo is a new laminated plastic much like the familiar laminated plastic on countertops, but tougher to take the scuffing of shoes and other hard things that come in contact with floors. It has a true-to-life look of a hardwood floor. It is backed by a thin layer of a foamlike material, which can be applied to concrete or virtually any other surface.

Q. Can I polyurethane a waxed laminated hardwood floor? I don't like the constant need to reseal and rewax the floor.

WAYNE WEBSTER, Littleton

A. I sympathize; sealed and wax floors may look great, but they do need regular maintenance, and the wax must be stripped first and new wax applied using a power buffer. No, you cannot polyurethane over wax. Remove it; apply generous amounts of paint thinner, let it sit on the floor for a minute or two, then scrub with the applicator cloth and wipe clean with a dry cloth. If all the wax is gone, polyurethane will do nicely: two coats of a high gloss.

Q. My house is only 12 years old and already it has squeaky floors. I plan to take up the carpeting over the plywood floor; how can I make sure the plywood is tight against the joists? The floor not only squeaks but sort of waffles when it is walked on. Six-penny nails were used to hold the plywood.

PAT TIERNEY, West Roxbury

A. At least you can find the joists under the plywood after taking off the carpeting, because any floor should be nailed onto the joists. If it is only one layer of plywood ( 5/8 inch is OK for a one-layer floor), you can use galvanized screws fairly closely spaced to hold the floor. The 6d nails used were long enough (2 inches) for one layer, but not long enough if there are two layers of flooring.

One layer is not standard construction, and since you get waffling of the floor when it is walked on, I think that waffling, or sagging between joists, is because the layer of plywood is too thin; 1/2-inch plywood will definitely waffle. And the more it waffles when walked on, the more it will pull out those nails.

So, the cure is to screw down the existing layer, then apply another layer of 5/8- or 1/2-inch plywood or OSB (oriented strand board), which is as good as plywood. Use 8d galvanized box nails or galvanized screws; 8d nails are 2 1/2 inches long, enough to go through the two plywood layers and about 1 1/4 inches into the joists. If you use screws, make them 2 1/2 inches long.

When a caller asked if he could find wood handles for a wheelbarrow, the handyman said he didn't think they were available separately, because wheelbarrows are sold in kit form.

Don Blodgett of Nashua, N.H., called to tell us that he saw handles sold separately at Home Depot in Nashua. Even wheels are sold separately, he said.

And if the bucket is sold separately, we could get a whole barrow. Thanks, Don Blodgett.

Q. My vinyl floor is 5 months old. Now there are a whole slew of what look like razor blade marks, about 300 of them throughout the floor. What are they and what can I do about them?

G.K., Billerica

A. Unless you walked on the floor with razor-blades attached to your shoes, they are signs of a defective covering. Contact the manufacturer and/or the dealer who installed it.

To the caller who asked for a good rust stain remover for toilets and things, the handyman found a marvelous cleaner, but forgot the name, which is no help at all. But as promised, the handyman went home and came up with this name: Rust Stain Magic (hydrofluoric acid), sold in supermarkets. It is best applied to dry surfaces, or at least one that is not under water. Since your stain is at the bottom of the toilet, you have to drain the toilet. To do that, close the shutoff valve under the tank, and flush the toilet once or twice. Most of the water will drain out. Use cloths to sop up the rest of the water, spray the Rust Stain Magic on the stain, and leave it for several minutes. Repeat as necessary.

When you're done, open the shutoff valve, let the tank fill, and flush the toilet once.

Q. What are the pros and cons of Pergo floors? I had linoleum on my kitchen floor but it got cut up. Ceramic tile is a good choice, but isn't it hard on the feet?

BILL DAVENPORT, Somerville

A. If you believe the TV ads on Pergo, it is the be-all and end-all of floors in every room in the house. In other words, perfect, and, I think, guaranteed 15 years.

Pros: It's a laminated plastic, which is very hard, resistant to wear, easy to clean, and needs no maintenance.

Cons: It's a plastic made to look like wood, and the handyman believes that it's a mistake to try to make anything look like wood. It just doesn't work, at least for him.

The 15-year guarantee is short for a floor, and plastic cannot be sanded for refinishing as wood can.

Being hard, plastic can scratch, and it is difficult to take a scratch out of any material, including linoleum, wood, and ceramic tile.

The cons are no reason not to buy Pergo, but ceramic tile might still be in the running for you because you may not find it that hard on the feet. The handyman (and others) have not had that experience with their ceramic tile.

And, you might be able to have your cake and eat it because there is a ceramic tile on the market that looks like wood, but has the durability and other assets of ceramic tile. It is made in Brazil, and George O'Brien, Box 321, Beverly, MA 0l9l5; telephone 1-508-922-5003, is the manufacturer's representative.

Q. My wide pine board floors in a reproduction house are showing a bit of wear and tear. Will resanding hurt the floor? Or should I refinish the floors another way, without heavy sanding?

P.C., Groton

A. It's an old wives' tale that heavy sanding will damage a soft-wood floor. You can sand a pine floor as many times as practical, as many times as any hardwood floor.

You can refinish one of two ways. If the floor is not badly or deeply scratched, you can sand lightly, with fine sandpaper, mainly to roughen the finish and reduce gloss, not taking much of the wood off. Then apply three coats of high-gloss, oil-based polyurethane varnish.

You could power sand with a belt sander or use the new square-plate floor sanders, available at rental stores. These new sanders are much easier on the floors and the operator than the old drum floor sanders.

The other way is to use a square-plate floor sander and sand three times, with coarse, medium and fine sandpaper; this is complete refinishing; then finish as above, with the three coats of polyurethane varnish.

The new square-plate sanders are excellent; they do a good job but are much gentler on the floor, and can be operated almost with one hand. The old drum sanders were powerful machines that ran so fast that the operator was hard put to keep from being pulled clear out of the house; they were also much harder to control and keep from gouging or rippling the floor than the plate sanders.

Q. I pulled up the rugs from my wide-pine board floors, and found black paper stuck to the wood. I would like to sand and finish the floors. How can I get that black paper up?

R.L., Medford

A. The paper is virtually welded to the floor; it is likely that no glue was used, so scraping will probably do it. Scrape the paper with a long-handled ice scraper, or any chisel-type device you can put your back into. If the paper is particularly balky, you can rent a power scaper that could ease the work. Soaking the paper with hot water may help. Once the paper is off, sand and finish. Contrary to popular opinion, there is no need for special care when sanding a softwood floor. Standard sanding is all you need.

Q. I am putting in a hardwood floor. What's better: red or white oak? How many coats of polyurethane varnish should I apply? Should the steps on stairs have more than two coats?

SHIRLEY MOFFAT, Everett

A. It is not a matter of what oak is better but what you prefer. Both will stand up equally well and, properly finished, will last indefinitely. Such oak, if it is the 3/4-inch strips, can be sanded three or four times.

White oak has a rather plain grain, will finish to an even, beige color, and is considered formal. Red oak is darker and heavily grained, with a fair amount of variation in color and grain. It is considered informal. Your choice is a matter of taste and preference, not quality.

I suggest you buy prefinished oak strips; there are several brands out there; Bruce is probably the best known of the prefinished floors, and offers two finishes: one is sealed and waxed, the other is four coats of polyurethane varnish applied in the factory. Choose the polyurethane finish.

The prefinished boards come in several widths and colors; some are slightly beveled on the edges, providing a small V-groove between boards as they are installed. This was done to compensate for slight variations in board thicknesses. However, manufacturers now can make the boards exact thicknesses, and you can get prefinished boards without a groove.

The difference is minor; some people are concerned that debris gets into the V-groove. It does not. If it does, it's easily cleaned. If you buy unfinished boards and plan to sand and varnish them, use two or three coats of high-gloss polyurethane varnish. For the steps, use three or four, but be informed that varnish will wear quickly on a step, because natural walking on steps is a scuffing motion, which is death on a finish. The ony cure for this is a stair carpet.

Q. I am picking up the wall-to-wall carpeting in my living room, and plan to put in a hardwood floor on top of the plywood. But I noticed a promotion for a laminated plastic that looks like hardwood. What do you think: Would this be as good as a floor?

B.M., Norwood

A. The material is very new, so if you use it, you will be making yourself sort of a guinea pig, a test case. Try it and find out. The Handyman is not enamored of materials that are supposed to look like something else, but what the heck -- you are the guinea pig, not him. The plastic is stronger than the plastic that is put on countertops and cabinets. But being hard, it can scratch. And, most importantly, it cannot be refinished.

Q. I'm fretting over whether to use mahogany or cedar for the floor boards of my pressure-treated deck floor that has rotted out. What is best?

M. P., North Andover

A. Mahogany vs. cedar: It's a tossup; both are resistant to decay. Both will weather gracefully without treatment; cedar will darken more than mahogany and is softer than mahogany, so will show more wear and tear marks. Let's put it this way: If I had the choice, I would choose mahogany, although I just might say to hell with it and choose pressure-treated wood; your pressure-treated boards that rotted out I don't think were really pressure-treated. Some years ago, a lot of wood was stained green to make it look like pressure-treated wood. Many people were taken by this scam.

At any rate, whether you choose mahogany or cedar, the way you install those floor boards is most important. Done right, the boards will last many years, if not indefinitely. And the right way is to lay a 6-inch-wide strip of tarpaper on each joist, lengthwise. Fold it over each joist so it is slanting down on each side of the joist. Then install the boards with a three-eighths-inch gap. The tarpaper acts as a water shed, with water running between the boards and down the sloping tarpaper, out of harm's way, giving the board a chance to dry out after it stops raining.

This was done routinely before the invention of pressure-treated wood; in fact, lumber stores carried 6-inch-wide rolls of tarpaper just for this purpose.

When pressure-treated wood came along, builders got out of this habit because it was thought to be not needed any more. But it is still a good idea, whether you put down mahogany, fir, cedar, pine, spruce, or even pressure-treated wood.

Q. I have a beat-up maple floor that I plan to refinish. I like to use oil and turpentine, but am concerned about its toxicity, and the toxicity of any other cover. What is best to use?

G.R., Billerica

A. I don't think it's a matter of what is best to use, but maybe what is the most safe. Boiled linseed oil, which is the standard oil and turps mix, is toxic, and has a habit of producing emissions longer than, say, a varnish that dries and cures in a short time (several days), after which the emissions are minimal. An oil finish is soft and will tend to collect dirt.

Polyurethane varnish is a better finish, I think, because it hardens into a tough film that resists wear and tear, even though it can scratch easily. So, two or three coats of polyurethane varnish is good. I also think oil-based polyurethane varnish is better than water-based polyurethane varnish, although the water-based will relese fewer toxins. But the water-based finish requires five to seven coats. So, take your pick of the varnishes.

Q. I am having wood floors installed, but I don't want that quarter-round trim along the edge of the baseboard. I would like the boards to butt up against the baseboard. Can that be done?

MEG ZAKS, Woburn

A. Sure, it can be done, but you will regret it. Any wood board floor must have an expansion joint along its border, especially along the side where the boards are parellel to the wall. Such a joint is less necessary where the boards are perpendicular to the wall.

The purpose of the joint is to allow the boards to expand into that space when they gain moisture, and they will definitely gain moisture no matter what you do. If there were no joint, the boards would not have any space to expand into, and would buckle. So, one technique is to leave a 1/2-inch space at the baseboard, and cover it with the quarter round, called a shoe mold.

But you can have your cake, without using the quarter round. Remove the baseboard, lay the floor with the 1/2-inch joint next to the wall, and reinstall the baseboard on top of the floor, covering the joint.

Q. I am putting in hardwood floors after taking up wall-to-wall carpeting. Is there a difference between standard oak boards and prefinished ones? I don't like the idea of a space or a groove between the boards; I like a good, even, smooth floor.

SAL SPROFERA, Medfield

A. There's little difference, except for when the finish is applied. A factory-applied finish is a lot better than one applied in the field. I would opt for prefinished, because once it's in place, you don't have to sand it and finish it, which adds to the cost. The prefinished flooring is more expensive, but not outrageously so. Those grooves you mentioned between each prefinished board are shallow enough to be virtually invisible. They were made that way to ease the difference between the thicknesses of the boards. However, now some prefinished boards come square edged, without the groove. I would also opt for the prefinished boards that have four coats of polyurethane varnish. Don't get the sealed and waxed finish; such a finish needs frequent maintenance.

Q. My daughter has a 1950s house with a cork floor. How is it cleaned and protected?

BYRNE SULLIVAN, Scituate

A. Wash with medium to strong solution of Spic and Span and water, using a minimum of water. If the cork does not come clean to your satisfaction, sand it lightly to reveal new, fresh cork. To finish and protect, apply two or three coats of an oil-based polyurethane varnish.

Q. Some buffoon put polyurethane varnish on the slate floors in the living and dining rooms of the house I am buying. A floor man suggested taking it off with chemical paint remover. Will this work?

JANET ZINNER, Sharon

A. It certainly will make short work of the varnish, but taking it out of the grout will take more work and possible repeats with the remover, and scrubbing with coarse steel wool.

With the varnish removed, you might be content with how the slate looks. If the slate looks pale and washed out, you can treat it in one of two ways. One way is to apply Future. Some homeowners have had great success with Future, an acrylic floor polish for vinyl floors; others have not had any success with it. You have to take your chances.

Another way: Make a mix of one part boiled linseed oil and one part paint thinner. Apply this liberally to the floor, wait 15 minutes, then wipe it all up (all that is going to come up, that is) with a dry cloth. This mix will darken the colors of the slate but brighten them, and is unlikely to make the floor shiny. Dispose of oily cloths by burning them; left around they will spontaneously combust.

Q. A carpenter suggested I use prefinished oak strip flooring for my kitchen. Is such a prefinish as durable as sanding unfinished oak and applying several coats of polyurethane?

DAVID MALECKI, Southborough

A. I think the prefinish is much more durable than on-site application of polyurethane varnish, but it depends on what prefinish it is, and the prefinish to get is one with four coats of factory-applied polyurethane varnish. Another prefinish is a sealed and waxed finish, which I think is less durable, needs regular maintenance such as stripping and rewaxing and buffing, and is not the kind to buy.

Incidentally, the oak strips come with beveled edges, creating a small V-groove between each board. Or, you can opt for the non-beveled edges. Both will stand up well.

Q. I would like to keep my polyurethane hardwood floors as shiny as they were originally. How can I do that? They have dulled down considerably, but are in good shape.

JULIE SANTOS, Peabody

A. Even high-gloss polyurethane will dull down in a matter of months. It's the nature of the beast and cannot be helped. Live with them. You might be able to jazz them up a little by light buffing with a dry cloth. Avoid polishes, waxes, and the like; they could dull the surface even further. And especially avoid using a silicone-based polish; some silicones can turn the floor into a slippery, slidy skating rink.

Q. I had my maple kitchen floor sanded with four coats of water-based polyurethane varnish. It has failed prematurely and worn so much that I must have it re-sanded. Is there another way to get a good, hard surface that will not wear so fast?

RENEE GLAZIER, Newton

A. After re-sanding, apply three coats of an oil-based polyurethane varnish. But you have to get rid of every speck of that water-based material, because often water-based and oil-based polyurethanes are incompatible. Water-based polyurethanes have not cracked up to their ballyhoo, the handyman thinks; and in fact, it is generally recommended to install five to seven

coats of the water-based polyurethane.

And here's Jim Richards of Marblehead, who recommends his product: ASTM Type II moisture-cure, aliphatic polyurethanes (Marco MCI/21 is the product code). ``They are far superior in abrasion reistance and other film characterstics to either the oil-modified urethanes or the water-based variety. They are also VOC (volatile organic compound) compliant in both Massachusetts and California.'' And, they are highly resistant to darkening,

he said.

Generally, it is applied by professionals, although the do-it-yourself can buy it (it goes on the same as any other polyurethane), but the minimum purchase is five gallons. So, write to Richards at Marco Products, Box 471, Marblehead, MA 01945 or call (617) 639-0159.

Q. I'm having my floors refinished, sanded and varnished. One refinisher said he'd put on a coat of sealer and a coat of polyurethane; another said he'd apply two coats of polyurethane, adding that you shouldn't use a sealer. Why not and which would be the best finish?

L.H., Roslindale

A. Why not, indeed? It beats the heck out of the Handyman, but the Handyman has heard a million warnings about what to do and what not to do. I think most such warnings are old wives' tales. The finisher should have explained why ``you shouldn't use a sealer,'' and he probably didn't explain because he couldn't explain.

It all boils down to semantics: Just what is a sealer? A sealer is anything that seals, essentially something that penetrates the wood and makes it impervious to penetration of anything else. Polyurethane (varnish, that is) is itself a sealer, especially if it is thinned down for the first coat. Sometimes certain types of sealers should not be used; if the sealer is shellac, for example, it should not be used because it is incompatible with polyurethane.

The best finish? Two coats of anything, generally, is the best finish; you will be well off with two coats of oil-based polyurethane varnish. Some refinishers suggest three, and three is slightly better, wearing longer, and three is necessary on softwoods such as pine and fir. If you use water-based polyurethane varnish, then five to seven coats is recommended. And some water-based polyurethanes are not compatible with oil-based polyurethanes, so do not mix and match.

The Handyman put three coats of high-gloss, oil-based polyurethane varnish on his wide pine boards 24 years ago, and they are in remarkably good shape today. Of course, there are a lot of rugs on the floor, and there is a little wear in high traffic areas, but those areas can easily be touched up; in fact they have been touched up at least once. The point is, there still is no need for those floors to be refinished.

Q. I am taking up carpets and having my floors sanded and coated with polyurethane varnish. Is a polyurethane finish slippery?

STELLA DRUM, Woburn

A. No, no more than any high-gloss or semigloss finish. Any finish will be slippery when wet, but that cannot be helped. Do not use a silicone polish on the floor; it is this silicone polish and its related materials (no polish or wax is needed or desired on a varnished floor) that is fearfully slippery, wet or dry.

Q. I have a room of pine flooring and another with pine flooring that is sanded and finished with an oil-based polyurethane varnish. Now, the unvarnished pine floor has turned a very dark yellow in areas exposed to the sun. The floor is extremely light, as it should be, in protected areas. I would expect some contrast, but not like this. What went wrong? I don't dare do another pine floor.

BILL CHAPMAN, Scituate

A. A varnished floor will darken with age, but from what you describe, this is ridiculous. In fact, untreated wood will darken with age. Wood will darken with age even under paint.

I suspect it was the oil-based varnish you used. It was either defective or just one of those things.

The cure is drastic, because the floors have to be resanded. Either change brands of polyurethane or apply several coats (up to six or seven) of water-based polyurethane varnish, which will not darken or yellow as much as standard varnish. It is not as sturdy as oil-based varnish, hence the need for many more coats. I personally don't like water-based varnish, but I do recognize it as non-yellowing, or at least less yellowing.

One problem with applying water-based varnish is that every speck of the oil-based varnish must be removed because the two are incompatible. It says so right on the label.

Q. I am refinishing my wide pine floors. Can I do it with a hand sander or floor sander?

LYNN JONES, West Townsend

A. It depends on the hand sander. A little orbital sander will not work. A hand-held belt sander will, but it is more work than using a floor sander. This I know because I did two rooms with a belt sander, having taken up the boards and done them at my leisure in a neighbor's garage. Leisure, heck, it was miserable. A floor sander will do a better job (with either, you have to sand three times with coarse, medium, and fine paper).

But hope springs eternal, and you might compromise by renting a square plate sander, a floor sander but without the drum, like an enormous orbital sander. It can be maneuvered with little effort, and probably creates less sawdust. It might be a little tougher to sand the low surfaces of an uneven floor, but with perseverance, it will work, at much less effort than with either of your other suggestions. Another good thing about the square plate sander is that it will get into edges and corners, precluding the need for an edge sander.

Q. I am refinishing my hardwood floors -- sanding, staining and varnishing. What should I use for a stain and varnish -- latex or oil? Is a satin varnish OK? Can I use a roller?

J.G., North Falmouth

A. I think an oil-based penetrating stain is your best bet for staining a floor. These stains are semitransparent, with enough pigment to find a color of your choice, but not so much that the stain looks opaque. With such stains, you can control the amount used to control the color intensity. As for varnish, again it is my opinion that the oil-based polyurethane varnish is best. Apply two, possibly three coats of the varnish.

The water-based polyurethanes are tricky to use because they can be cloudy if care is not taken. Besides, at least seven coats of the water-based varnish are needed, indicating that it does not stand up as well as the oil-based.

A satin gloss is OK, too. I also think that is is better to brush the varnish on with a quality brush; it will penetrate the wood better, and subsequent coats will adhere better to previous coats. A roller also may give an orange-peel finish; that might be OK on a refrigerator but not on a floor.

Finally, remember this: Apply thin coats. Thick coats can wrinkle, can alligator, and can take excessive time to dry and to cure. A thick coat also may be more likely to peel.

Q. When I had my new kitchen floor done with plywood and linoleum, it came out 1. book page three-eighths of an inch higher than the neighboring room. A man put a threshold in the doorway, covering the floors, but it is 2 inches higher than the floor, and is a real hazard. What can I do?

C.M., Wilmington

A. Tell the man to take that 2-inch monster (it sounds like an exterior threshold to me) out and install a three-quarter-inch oak threshold in its place. It can butt up against the higher kitchen floor, and is tapered along the edges for a nice, easy transition. Or, set it on top of the high floor.

The Handyman has these all over his house, including one with a 2-inch drop, and they all work well to guide walkers (people who walk, that is) over them.

Q. How can I maintain and clean newly-polyurethaned floors? How about scuff marks?

FRAN OLFE, Brookline

A. Dry-mopping and vacuuming will keep the floor clean. For stubborn spots, damp-mop with water, but only damp, not wet. For scuff marks, put a little oil on the marks, wait 10 minutes, and wipe clean. For stubborn scuff marks, scrub lightly with Brillo or SOS pads.

Q. I plan to put in a laminated plastic floor (Formica Brand) over some old boards in an attempt to control scratching and wear and tear from all my puppies. It also will make the floor easier to clean. Would this work?

B.J., Arlington

A. A laminated plastic floor is new to me, although I did see a commercial about it recently, one of those teaser types that didn't say much.

Although virtually anything, including ceramic tile, will scratch, the idea of such laminated plastic sounds good to be as resistant as anything, even more so. Go for it. It has a wood look and you can make yourself a guinea pig and see how well it works. It is sold by Newton Floorcraft Vinyl Flooring Tile & Carpet Company in Watertown.

And, in fact, there is a ceramic tile on the market that looks like wood. George O'Brien of Beverly, a representative for Sant'Ana, a Brazilian tile manufacturer, sent us samples of ceramic tiles that look like real hardwood flooring. The tiles are 5316 inches wide and 15 1/2 inches long, a funny shape for tile, but adaptable to setting in a parquet fashion. O'Brien said they come in six colors, each with a wood tone, and there are several variations of texture in each color. The price is competitive, about $3.50 to $4 per square foot.

So, B.J. could opt for such a tile floor.

While even ceramic tile can scratch, it has a good chance of standing up well and long against those sharp puppy claws. Easy cleanup, too. William Smethurst of Malden is the distributor.

Q. I plan to put plywood on my attic floor, for storage purposes. Should it be 3/4 inch, or can I get away with 1/2 inch? Also, the plywood will go over recessed lights, where there is no insulation. Would plywood over those lights allow the lights to heat up excessively?

PAUL O'BRIEN, Duxbury

A. In a word, yes: the plywood could hold the light heat in, causing a fire hazard. As for plywood, you could use 1/2-inch, but 5/8-inch would be better because it will not sag or bounce as 1/2-inch will. It is not a matter of safety or structure, but rather comfort and peace of mind that you did it right.

As for the plywood over the lights, drill holes in the plywood for ventilation. If the plywood panels meet over the lights, open the seam to 3/4 inch.

Q. A hot lid was dropped on the oil cloth on my kitchen floor and made a round scorch mark the size of a plate on the floor. I tried turpentine to remove it without success. Is there any way to save that floor?

A.P., West Roxbury

A. Oil cloth? That is a word from the past. You mean sheet vinyl flooring. As for removing the scorch mark, if it has not bubbled up from the heat, you can try this: Scrub with Brillo or SOS pads, or sand lightly with fine sandpaper to take off the very top finish of the vinyl. If that lightens up the mark enough, apply a floor wax on the entire floor.

If that doesn't work, your only recourse is to double-cut a patch. Find a similar sheet vinyl a little bigger than the mark, tape it over the mark and cut through both the patch material and the original. Remove the patch. Apply heat from a hair dryer on the original vinyl and pry it off the floor. Scrape off any glue residue. The patch will match the cutout portion. Glue it in place with an adhesive caulk or vinyl adhesive.

Q. I am having my floors sanded, and plan to finish them. But how can I fill all the holes left in the floor after I pried up a carpet-tacking strip?

ALBERT COMMITO, Medford

. Ah, that is one of the handyman's favorite tricks: filling the holes without smearing the filler material all over the floor. Buy a filler material to match, or closely match, the color of the finished floor. Apply one coat of varnish or whatever finish you will use, then fill the holes; that way, any smearing on the floor can be cleaned up with a wet sponge. The first coat keeps the filler from penetrating the bare wood, after which it is very hard to remove. The filled holes will show some, but since they are next to the wall they will be virtually unnoticeable.