Q. In my small Cape-style house that is 14 years old, I have a ridge vent and full-length soffit vents, but the builder blocked the gable vents. Why? Another small matter: I have lost a few asphalt roof shingles. How can I replace them? Some of my other shingles are not loose, but they are not glued down like most of the shingles are. Can I put a dab or two of glue under them to keep them down?
A. The gable vents are closed because if open they would interfere with the efficiency of the ridge and soffit vents to exhaust air. Keep them closed. You can replace a shingle. Make sure the old one is completely out, and tap down any nails that might be sticking up. Insert the new shingle so that it lines up with the bottom edge of its neighbors, and dab some roofing cement under the bottom edge. Lift the shingle above the replaced shingle so you can nail it, usually at the top of the slots in the shingle. As for the flapping shingles, the glue that used to hold them down wore off, or didn't take hold if they were installed in cold weather. The cure is to lift them a bit and put three or four dabs of roofing cement under the bottom edge, up about an inch or two. Roofing cement is the right glue to use, and you will be glad you did. It comes in cans and caulking cartridges. You can use the cartridge in a caulking gun; do this in warm weather so the cement will flow.
If you are uncomfortable or fearful being on the roof, get someone to do it.
Q. My hip roof needs replacing. I have had two offers: One is to go over the single layer of shingles with a 50-year shingle, and install an ice and water shield along the lower edge of the roof, on top of the old shingles. Is that right?
TONY ODOMS, Dorchester
A. It is OK to put new shingles over the old layer, but putting the ice and water shield over old shingles is not right. An ice and water shield, which is a rubberized membrane 3 feet wide, must, or at least should, go over bare sheathing. It is designed to prevent backed-up water from an ice dam from leaking into the attic, causing all kinds of problems. Applied over the old shingles, it might do this, but it may not stick well to the shingles and may also not do its job. So, 3 feet of shingles should be removed and the ice and water shield applied. When new shingles are installed, you will never notice any area where the original shingles were removed. Stick to your guns and insist on this. The other proposal, to take off the old shingles, is OK but not necessary, and will cost extra. But it will be a good surface for the ice and water shield.
Q. Can I put new ceramic tile over old ceramic tile in my bathroom?
AUDREY DERANY, Needham
A. Yes, if the floor is sturdy enough to take the extra weight, which is not much in a small bathroom. In almost all houses, the floors are sturdy enough. Install the new tiles with a thin-set mortar. The only other thing you have to do is lift the toilet, because it must go on top of the new tile.
Handyman on Call also appears in the Globe's Real Estate section on Sundays. Peter Hotton is available 1 to 6 p.m. Tuesdays to answer questions on house repair; call 617-929-2930. Hotton chats online about house matters 2 to 3 p.m. Thursdays, at Boston.com. Hotton can be reached at firstname.lastname@example.org