For surfside deck, mahogany weathers well

NANCY SUSSMAN, Rhode Island

A. I suggest mahogany that will weather nicely to an even silver in that salt air. It can be bleached or cleaned when needed, and in the future can take a semitransparent stain if you like.

Pressure-treated lumber by the way, is different from the old arsenate stuff, and safer. But here is a trick that you should suggest to the builder. Since the advent of pressure-treated lumber, many installers have forgotten this trick that will help prevent decay: Put a 6-inch-wide strip of tar paper along each joist for its full length, bend the tar paper down a bit, then install the spaced floor boards. This will allow water to drain away from the boards where they sit on the joists. It’s a minor matter, but it is easy and does a great deal of good.

Q. Since I converted my heating system from oil to gas, I am getting a lot of water on the bottom of my stainless steel chimney cap. So much water is dripping down the stainless steel flue liner that it is rusting out the galvanized smokepipe coming from the heater. I have already filled several big buckets of water coming out of that pipe. What’s wrong, and what can I do about it?

TONY, Swampscott

A. Nothing’s wrong, and what you can do is give the gas company a swift kick in the slats for not telling you about this very common phenomenon. What they did not say is that each cubic foot of gas burned creates 2 cubic feet of water vapor, which is a whole lot of water vapor. This water vapor swooshes up the flue and condenses when it hits something cool, such as the chimney cap, then drops down the flue to rust out the steel smokepipe. Just for the record, oil does not create as much vapor.

What else you can do: Take off the chimney cap. Then the water vapor will rise above the chimney and condense in the cool air, coming down on the roof as rain. Or convert your system to one that uses a power vent through the wall instead of up the chimney. If that vent is high enough and long enough, the condensation that comes out of it will not hurt anything.

Q. My 1977 house was built with Texture 1-111, a plywood vertical siding, nailed directly on the studs. Some of the siding has rotted out, mainly toward the bottom of the 4-by-8 sheets. Is it possible, or practical, to replace the rotted parts and continue with the solid color stain, which has held up well for years without peeling?

Shelton, Conn.

A. All of the above. Texture 1-11 is rather sensitive to decay toward the bottom of the sheets, but if bad areas can be cut out and new ones installed without an obvious joint line, then go ahead. You’ll be good for another 32 years. You are particularly lucky to have that solid color latex stain stand up so long. Keep up the good work.

Q. Water just pours like Niagara down one valley of my roof, saturates the ground, and then leaks in to the basement, messing up the walls and the plumbing. How can I stop it? I don’t have gutters and would like to avoid them.

Watertown, N.Y.

A. You can’t avoid gutters here to catch the water, unless you put in a huge barrel to catch it. Then you can use it to water the garden. But you need only a relatively short gutter, perhaps three feet on each part of the L-shaped gutter you will use on that corner. If there is no corner, use a straight run of gutter, but in either case, get the biggest, strongest aluminum gutter possible; you may need a custom one. Put a large baffle on the front of the gutter to keep the cascade from overflowing the gutter. Put in one downspout, and at ground level put in an L and extend the spout at least 10 horizontal feet from the house.

Globe Handyman on Call Peter Hotton is also in the g section on Thursdays. He is available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton also chats online about house matters 2-3 p.m. Thursdays. To participate, go to www.Boston.com. Hotton’s email is photton@globe.com