Ask the Carpenter: Replacing a rotten sill plate

Ask the Expert Home Improvement
. AP

Q. We bought a 1938 home seven years ago, and just discovered that the original cast-iron drain pipe from our kitchen sink failed and has been leaking down the exterior wall probably since before we moved in. We’ve had the pipe fixed, but about 3 feet of the sill plate underneath the drain is rotten — poke-a-screwdriver-through-it rotten. Is it possible to cut out the rotten part and replace it with a fresh piece, or is it an even bigger job than that? Second, how do we find the right kind of contractor for the job? Considering the importance of the sill plate to the home’s structure, it seems we would need more than the average contractor. My husband has done a lot of carpentry, but we don’t want to take any risks with this one. Thank you.

S.H. and S.R., Needham

A. Actually, this is a straight-forward repair that many carpenters can handle. This type of repair is always easier if you can access the sill plate from the basement, but oftentimes we do the work from the outside. I’m betting that this area is also under the kitchen window, meaning that the window header is probably spanning the damage — which can reduce the need to support the house while removing the sill plate and replacing it.


Q. My home has a forced hot air heating system. It takes in no outside air, circulating only “house’’ air. My wife says she can smell the basement when the fan runs. Is there any benefit to having the system modified to bring in fresh air from the outside?


A. You should call your HVAC service provider and tell them about this issue. They might be able to add a fresh-air intake. Maybe some other readers have a solution as well?


Q. We recently had our chimney rebuilt with a new liner to the basement. The contractor has to add a cap. Should the top be equal or larger than the length and width of the chimney? I have read that this helps to keep the elements away from the chimney. Also, he will use a metal/masonry adhesive to secure it to the crown. I have read that this is better than screws, because moisture can seep in around them, but will the adhesive be strong enough against high winds? Should they add screws on the corners after it’s sealed?


A. Do you mean the top screened space? If yes, there must be at least 5 inches of clearance between the top of your tallest flue and the chimney cap lid. You can use either adhesive or Tapcon screws (masonry anchors) to attach the flanges to the chimney. I’m not sure what is the best practice, but my gut tells me that mechanical fasteners (screws) will withstand high winds better than adhesive. I’d use both!

Rob Robillard is a general contractor, carpenter, editor of, and principal of a carpentry and renovation business. Send your questions to or tweet them to @robertrobillard. Subscribe to our free real estate newsletter at