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Ask the Carpenter: Cracks in the basement, rodents in the garage

Ask the Expert Home Improvement
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. AP

Q. The basement floor in the home my parents had built has a long crack running from one side to the other. Can this be corrected by laminating the basement, which is damp?

GINNIE MAYHEW

A. Cracks are a common sign of settlement. You should be concerned if you see any of the following:

■ Gaps forming between the floor and walls

■ Gaps forming between the walls and ceiling

■ Walls pulling away from each other

■ Cracks on the walls, especially near the corners

■ Doors or windows that cease to open correctly or floors and surfaces that noticeably slope

If the floor crack is seeping water, you can’t stop that with an injection or a patch. You’ll have to relieve the hydrostatic pressure by installing an interior drain tile. With drain tile in place on the inside of foundation footings, the ground water under pressure has somewhere to go — the pressure causes it to seep through the gravel bed surrounding the drain tile and into a sump pump.

That said, concrete basements will always crack. Usually, small cracks rarely impact the structural integrity of your home. Bigger cracks or those caused by instability of the soil beneath your house can lead to serious issues. If you notice significant cracks in your basement, make sure to have them inspected by a professional to identify their damage potential.

 

Q. We have an HVAC unit in our attic and would like to add insulation to the rafters bays to make the entire space conditioned. The attic is for storage and won’t be finished. In the Boston area, what type of insulation should we use: open or closed cell? We know closed is more expensive, but want to get the right product for our conditions.

M.B.

A. I reached out to my spray foam contractor, Frank Bood at InsulationDoneRight.com. Frank recommends closed cell because of its high R-value per inch; many homes in the Boston area have small roof rafters. Closed cell will also prevent moisture from getting to the roof deck.

 

Q. For two years now, squirrels or chipmunks have been chewing up our new garage door, both the wood and the plastic edge. I may have left bird food in the garage years ago. I definitely try not to leave anything tasty in there anymore. I tried capturing the animals with traps, but they seem smarter than I am. Do you have any advice?

A.A.

A. I’m guessing that they smell or think there is food in there. I reached out to Matt Carr at Concord-Carlisle Pest Control for advice. Matt says you probably have mice. He recommends putting snap traps on the inside to the sides of the bay doors. Mice feel the temperature fluctuations when they’re out searching for food and want to investigate. Also, when mice travel, they drop bits of urine as scent markers because they can’t see well. When other mice pick up this scent, they think there’s a mouse party going on in there and don’t want to be left out.

Interesting tidbit: Mice can climb almost anything (including wallpaper) and gnaw through aging mortar.

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. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.