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Handyman on call

The truth about roof ice and water shields

By Peter Hotton
Globe Staff / September 29, 2011

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Q. I am putting on a new roof, and got two estimates about equal in price. One roofer said I need an ice and water shield on the roof, adding that he would put the shield over the asphalt shingles. The other said I don’t need any ice and water shield when he puts new shingles over the old. Who’s right?

JOSEPHINE ALFONSO, Plymouth

A. Right or wrong? Good question. Have the roofer who suggested the ice and water shield put it on bare wood. Then add shingles on top of it. If there is one layer of shingles on now, it must come off. The other roofer was partially right because he would add one layer of shingles to the present layer. This is not the best idea because every roof needs an ice and water shield. Years ago, when ice dams caused lots of leaks, it was recommended to put on a 3-foot strip of ice and water shield (rubber-like membrane) along the bottom edge of the roof to prevent water ice dams backing up under the shingles and leaking into Later, it was determined 3 feet was not high enough. So they tried 6 feet, with the same result. Now most roofers put the shield on the entire roof.

Q. I had a big pine tree cut down, and when it fell and was cut up, it left a lot of sap on the asphalt driveway. The sap looks like white streaks, and I can’t scrape it off. How can I remove it? Also, my basement has 8-inch tiles that I think contain asbestos. How can I treat them? Can I put new tiles over them or should I remove them?

SCOTT, from Andover

A. Denatured alcohol will soften, maybe even dissolve the sap, and then you can scrape or wipe it up. The tiles are probably 9 inches square, and are vinyl asbestos, and contain relatively little asbestos. Leave them alone and they will not be a hazard. Just don’t sand, nail, or cut them. You can cover them with 12-inch square tiles, or better yet, big ceramic tiles put down with thin-set mortar.

Q. My basement has a sump and pump that works well to keep water out. I was thinking of getting a gasoline generator to operate the pump in case of a power failure. What size generator should I get, and who makes them?

WEST ROXBURY

A. Honda is one maker. As for the size, it does not have to be very big. Ask the dealer for what size to use. Instead, you will be better off with a pump that has battery backup. The batteries are good-sized and hold a charge for a long time.

Q. My wrought iron railing is painted white, and by the time Tropical Storm Irene came along the railing rusted at the joints and connections. The railing man came back, sanded off the rust, and repainted. The rust came back. What now?

RAY BUXTON, Bedford

A. The rust never left, it stayed in the joints because the paint was defective. At least I think so. To correct this, sand off the visible rust, then sand the white paint as thoroughly as possible. Treat remaining rust with Rust Reformer or other treatments that contain phosphoric acid, which will turn the rust black and make it paintable. Don’t use white paint. Buy Krylon Contractor’s wrought iron paint or Krylon’s Door & Shutter paint. Both are black, and neither one needs a primer.

Q. My shed has cedar siding rough side out. I would like to allow it to weather to that popular gray color. What should I put on it?

STEVE

A. Nothing at all, and in about two years it will weather nicely, but being red cedar, the gray will be fairly dark. Or, apply a clear sealer and wait two years before applying another coat of sealer. Two coats will not work because the first coat of sealer will penetrate the wood and seal it against the weather. A second coat will bead up on the first and the second will never dry.

Q. The paint on the inside of my microwave is peeling. I asked a friend if he would paint the inside, and he said, Oh, no, paints are toxic so it’ll not do. So I still have the problem: Can the inside of the microwave be painted?

CURIOUS

A. Ask your appliance dealer. If the unit is under warranty, you may be able to get a new one.

Globe Handyman on Call also appears in the Sunday Real Estate section. He is available 1-6 p.m. Tuesdays to answer questions. Call 617-929-2930. Hotton (photton@globe.com) also chats online about house matters 2-3 p.m. Thursdays. Go to www.boston.com