Improper window installations are one of the biggest problems contractors and manufacturers face on the job. Traditionally, framers have always installed doors and windows for the contractor. Now contractors increasingly are using professional door and window installers to take the burden of this work off the framers so they can do what they do best. Having specialists install windows helps ensure that the products are installed correctly. Here is a proven way to install windows so there won't be callbacks to the contractor. It involves five basic steps:
Presumably, the rough window opening has been framed according to the specifications of that particular window. If not, measure the window and frame the rough opening 1/2 inch larger than the window's width and height. This will allow you a 1/4-inch clearance around the window for shimming adjustments.
1. Cut lengths of house wrap into 18-inch wide strips. Starting from the bottom, stretch a length of wrap across the opening so 10 inches extends below the rough sill. Cut the wrap next to the opening on each side and fold that piece over the rough sill. Staple it in place. Repeat this process on both sides and the top of the opening. When finished, you will have an opening wrapped with a ten-inch border on the outside and folded over to cover about 8 inches inside the opening. Staple the material down firmly in each corner to protect the studs from any moisture that may leak in around the window.
2. Stack two layers of foam Sill Sealer on the rough sill and staple in place.
3. Before setting the window into the opening, run a bead of silicone-based caulk all the way around the inside of the window's nailing fin. While one person holds the window in place, the other slips shingle shims between the window and the rough opening to make sure the inside gap is even all the way around the frame. The gap should be about a 1/4-inch. Use a level to ensure the window unit is level and plumb. Shim as needed, then tack each corner of the bottom fin.
With the person outside still holding the window in place, unlock the window sashes and open both the top and bottom about a 1/2-inch. This applies to sliding and double hung or single-hung windows. This gap should be even from top to bottom on a slider or right to left on a double- or single-hung. If necessary, use shims to move the window so the sashes are all aligned. Once the window is square, finish nailing completely around the window fin. Double check your reveal to make sure the window didn't move while it was being nailed.
4. The next step involves using a good quality window tape made especially for taping around windows and doors. The tape comes in 50-foot rolls and is about 4 inches wide. Starting at the bottom, stretch the tape over the fin, with the top edge right next to the frame. Extend the tape beyond the fin on each side the width of the tape, or about 4 inches. Cover each side fin in the same manner. Finally, tape over the top fin and cover the ends of the tape on the sides. Now staple each corner to hold the tape down in case of strong winds.
5. For the final step, fill the 1/4-inch shimming gap between the stud and the window frame on the inside with low-expansion foam. Don't over do it! This forms a final barrier behind the nailing fin all the way around the window. This is the fifth and last preventative step to keep water out. The next day you can then remove the shims and foam the little spaces that are left.
I know this seems like overkill but we haven't had a call back for a leaking window for four years. That's about 38,000 windows. Not bad!
Author Profile: Guy Lundsten is founder and president of Installation Masters in Spring Lake Park, MN. His crews install about 800 windows each month.