Do It Yourself: Use foam around window frame gaps
Q. I plan to install several replacement windows myself. What should I use to fill the gaps around the perimeter of the replacement windows and the existing window frames?
A. It used to be standard procedure to pack fiberglass insulation into the gaps, which should be quite narrow if you have sized your replacement windows correctly. The fiberglass was pushed into the gaps with a putty knife, screwdriver or similar tool.
However, most experts now recommend using expanding foam insulation to fill the gaps. You can buy this insulation in aerosol cans at most home centers and building-supply outlets.
The foam is faster and easier to use and insulates better than fiberglass. The product should include a narrow nozzle that lets you squirt the insulation into small cavities without making a lot of mess.
It is important to get the correct type of expanding foam. The container should clearly state that the foam is for window and door use; DAP and Great Stuff are among brands available.
These special foams expand with less force than some regular expanding foam insulations. This is important because too much expansion can distort the frames of the replacement windows, causing binding that can make them difficult to open and close.
Insulating the small gaps around the new windows is important to get full energy efficiency from the windows.
Q. I have a large deck built of pressure-treated wood. It was built in two stages and I have noticed that some of the boards on the newer section are shrinking, leaving gaps. Also, the deck was originally stained but a contractor who did some repairs coated the entire deck with a water-proofer. Could that be responsible for the boards shrinking? What should I do now?
A. It is normal for pressure-treated boards to shrink across their width. The shrinking is caused by the evaporation of water, used in the treating process.
Cheaper grades of treated wood contain more water than better grades, so they can shrink more and also often develop small cracks called checking. Even premium-grade, kiln-dried treated wood will shrink some in time.
I wouldn’t worry much about the shrinking unless the gaps get wide enough to cause accidents such as tripping. If that happens, you might want to have the deck resurfaced with a better grade of decking (composite decking is more expensive than treated wood, but doesn’t shrink).
As for the “water proofer” – whatever it might have been – I don’t understand why a contractor would apply that to a stained deck. Most stains contain water repellents, and in my opinion it would have been better to clean the deck and apply a new coat of stain.
But if the water proofer is not peeling or causing an appearance problem, I would wait a year or so, then give the deck a thorough cleaning and a new coat of stain.