Tips on Installing Windows

For maximum efficiency, follow these tips on window installation from an expert.
By: Dwight Barnett
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Q: I have been doing construction for more than 25 years now, and have seen the problems you talk about (in this column). But the one that doesn't get much focus is proper installation of windows. Commercial contractors are finally getting it right, but residential contractors or home builders just won't do it. They all try to jam the brick as tight as they can to the window frame, and in no time the window won't function properly. Your client is in for window problems in the future. Please comment about this problem. — M.M., Evansville, Ind.

A: First, all windows leak. Can't stop it, so you have to prepare for it. I advised the client to use a three-inch-wide ice shield to wrap the wood frame of the window opening before the exterior house wrap was installed. Before the windows were installed, the house wrap was taped and sealed at all window and door openings and at seams and utility openings.

As the windows were being installed, the nailing flange was sealed on both sides using silicone caulk. Any water that penetrates the window will be forced to flow down the wall between the house wrap and the backside of the brick veneer.

Did you note the weepholes at the base of the brick walls?

Second, homes are made of wood; wood shrinks as it dries. Because of gravity, anything attached to the home's wood framing will move in a downward direction. Depending on the species of the wood used for rough framing, the shrinkage can be as much as three-eighths of an inch vertically.

For a second-story frame home, that equates to three-quarters of an inch at the upper windows. That's a lot of movement to be accounted for.

The brick veneer does not shrink and is not attached to the wood frame, except for the brick ties, which are somewhat flexible vertically. Therefore, the brick must be considered a stationary object. As the weight of the home forces the window downward, squeezing the window against the stationary brick, the exterior portion of the windows sill will bow. If you have double-hung windows, the bowing leaves a gap on either side of the lower sash where weather can penetrate the home.

If you have casement windows that crank open, the pressure on the bowing sill will make the window inoperable. Sometimes you can force the window open, but you'll have trouble cranking it closed. My client chose casement wood windows, and we had to make preparations for the inevitable movement, so I asked the builder to hang the window in the opening with a one-half-inch gap at the bottom rather than simply setting the window in the opening and nailing it in place.

For a second line of defense, the brick sills of the home are not up and under the window framing as you thought.

The trick is to make it look that way. The brick sills were cut to fit even with the front of the window where caulking was then used to prevent weather entry. When this home begins to shrink, the window will slide down behind the brick sill, and it will be left to the owner to maintain the caulking.

You are right, however, that some brick layers make the brick snug at the sill and do not plan ahead for shrinkage and movement.

(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors.)

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