Real estate

ASK THE CARPENTER

How much insulation do you really need?

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Can you get away with applying spray-foam insulation in only problem areas?

Q. Is it useful if spray-foam insulation is applied only to the areas where ice dams occur, not the entire attic? We have a very large attic with a roofline near the center of the house that causes snow accumulation. The roof is too far off the ground for us to use a rake. Additionally, if we use spray-foam insulation and then later we need to replace the roof shingles, would we have to apply the spray foam again? Is the spray foam damaged by roofing removal/repair?

PEG O.

A. I’ve installed spray foam in knee-wall crawlspaces in finished attics, but I don’t recommend it. If you can access the entire underside of the roof, I’d opt for spraying the whole surface. I reached out to my friend Frank Blood at InsulationDoneRight.com, and he confirmed my suspicions; using spray foam in only the problem areas will create ice damage higher up on the roof.

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In a traditional structure, the roof melts the snow. It’s the bottom foot or so of the roof that is cold, and this is where the ice forms. By creating the cold spot higher up, there is more of a chance of ice damage, because ice and water shield protects usually only the first 3 feet of the lower section. The upper part of the roof typically only has felt paper, which is as easy to penetrate as it sounds. The best thing for you to do is have a professional look for solutions that best suit your needs. The whole roofline is typically the best option, but you may not need that.

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With regard to re-shingling, you will not have to replace any foam if you change out your shingles.

Handout
Sometimes you can bleach out a stain in wood.

Q. My kitchen is in a one-story ell to a dormered Cape a previous owner built. The ceiling is pine boards, each about 10 inches wide and with a satin-finish stain applied 30-plus years ago. There are three hand-hewn beams that appear to support the structure. One runs the width of the space, roughly 15 feet, and the other two are shorter due to a jog in the room. The roof leaked in several places a few years ago and was replaced. There are no active leaks. I’d appreciate any suggestions you can offer regarding how to conceal, cover, or treat the stains left behind. I plan to upgrade the kitchen and would like to get rid of the ceiling stains as well. Thanks.

MAUREEN

A. The boards look almost natural. Are you sure a stain was applied? If it was, the simplest way to cover up the stains is to paint your ceiling. I’d wash the ceiling, seal in the stains with a quality primer-sealer, and then apply two coats of paint.

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If you find that the ceiling is actually a clear wood, you can try bleaching out the stain. (I hate working overhead like this — crick in neck!) Mix oxalic acid wood bleach in a plastic container according to the manufacturer’s directions. Cover everything in the area below this stain, and be sure to wear eye protection and gloves.

Use a wet sponge and apply the bleach in an even coat. Wait the amount of time the manufacturer recommends, and then with clean water and a rag or sponge, wipe the mixture off the ceiling. Repeat as needed to remove the stain. Use clean water to wipe the area down afterward. A light buffing with fine-grit sandpaper, rubbing with the wood grain, can sometimes be done to feather in and blend different colors in wood.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @robertrobillard.