Insulating the floor of three-season porch
Q. We have a three-season porch, with a roof and enclosed glass sliders. My husband wants to insulate under it. Is that OK, and will it do any good?
CURIOUS
A. Insulation primarily prevents the loss of heat, so there won't be much of a benefit from insulation under the porch. But there will be some, enough to be worth putting it in. It will be very useful if you add a little heat (such as a small space heater) in the porch.
Q. I have a patio and walk of bluestone blocks, some of which have gotten very dirty, and stained and scratched, with chips of stone coming off the blocks. They are a mess, and very unsightly. My roofer, who was doing some repairs, suggested that I simply turn the blocks over. Sounds like a good idea.
JOHN, by phone
A. OK, John, you can trust your roofer. What he said is exactly what you can do, because the blocks are set in sand and not mortared. Turn them over and they will be good for another 40 years or so.
Q. I want to replace trim on an outside window. Am I OK replacing the wood and caulking, or do I need to put flashing behind to keep water out?
DAN, in Hotton's chat room
A. It may depend on the age of your building, but in almost all cases, flashing is most important, because it allows water to drain away. Caulking, which tries to block the entry of water, almost never works. The normal flashing around a window is a strip of roofing felt (tarpaper) on the sheathing along the top and sides of the window. You may already have some of this tarpaper. If so, keep it. If not, try to put some in, as best you can. Some is better than none. As for the top trim (casing), you need window flashing, a pre-formed aluminum strip that fits behind the siding and over the top of the casing.
Q. I have a limestone front step. This spring it is covered with black spots, some the size of a dime, others like dots. I used bleach and they disappeared, only to return when the surface dried out. Now what?
DALE RUSHLOW, North Attleborough
A. It certainly sounds like mold, especially the small dots. But since bleach did nothing, try this: Power wash it. Or sand it with medium sandpaper. If these attempts fail, mix 4 ounces oxalic acid in a quart of hot water, and put this on the stains. This solution normally takes rust stains from concrete and many kinds of stone, so why not try it for the dark spots.
Q. I read recently that you mentioned a man who makes custom-sized doors. Bulkhead doors, I believe. Do you have his name?
INTERESTED
A. Sure do. He is Joe Cavallaro and he can handle any bulkhead under the sun. Call him at 781-828-4645 or 800-553-4301.
Globe Handyman on Call also appears in the Sunday Real Estate section. He's available 1-6 p.m. Tuesdays to answer questions about house repair. Call 617-929-2930. Hotton (photton@globe.com) also chats online about house matters 2-3 p.m. Thursdays. Go to www.boston.com. 
