How to Install a Window

By: Scott Gibson, This Old House magazine

Shopping List

Supplies You Will Need

1. WINDOW

2. CAULK

3. MINIMIALLY-EXPANDING FOAM INSULATION

4. 15-POUND BUILDER'S FELT
an alternative to membrane for flashing the rough opening

5. WATERPROOF MEMBRANE

6. METAL FLASHING

7. FOAM INSULATION

8. 1 1/2-INCH ROOFING NAILS
for fastening nailing fins to the sheathing

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Tools List
Tools You Will Need
- 20-ounce hammer
- 2-foot and 4-foot levels
- Hammer-tacker,
  for stapling builder's felt
- Utility knife
- Measuring tape
- Caulk gun
- Optional: Drill-driver and 1 5/8-inch stainless screws,
  for attaching sill extender to bottom of narrow aluminum sill
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Introduction
Overview
Steps:
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9

2 to 4 hours per window, depending on window size
Cost of window, plus $30 to $50 for other necessary materials

Difficulty: Moderate To ensure a waterproof, smooth-operating window, you must work methodically and not skip any steps

Windows do a lot: help establish a home’s visual character, let in light and air, and frame views from inside. But if not installed correctly, they can become unwelcome avenues for water. "Rot around windows, even in relatively new houses, is one of the biggest problems I see," says This Old House general contractor Tom Silva. "You can't depend on just the trim and the housewrap to stop water."

That's why whenever Tom puts in a window, he makes sure to seal the perimeter of the opening with sticky sheets of self-adhering waterproof membrane, strips of metal flashing, and judicious amounts of caulk. Any rain that gets by one of these layers will be stopped by another.

His final step, once the opening is watertight and the window is set plumb and square, is to plug the gap between the window and the framing with foam insulation.