How To Install a Window
Time Required: Over 1 day
While each window manufacturer has specific installation instructions for the wide range of shapes, styles and construction types available, on the whole, windows are installed in the same manner.
This guide will show you how to install a replacement window or new one in your home. A complete list of required power tools and materials can be found at the bottom of this page. When performing residential window replacement or window repair, keep the old windows in place until you have inspected the new ones for damage and verified their size.
If you’re interested in having one of our professionals complete window installation for you, click here to schedule a free in-home consultation.
Tip: Pre-hung windows come complete with finished frames, and you can insert them in one piece into the rough opening left by the old window.
Safety: You can rent scaffolding to safely install windows on upper levels of your home. Because windows are difficult to handle, find someone to assist you when working above the first floor. Always wear eye and hand protection when you replace window glass and fiberglass insulation.
Tools & Materials
- If replacing a damaged window, be careful to avoid jagged glass. Use painter's tape to cover any cracks to prevent shards from falling during the removal process.
- Center the new window in the opening, supporting it with wood blocks and shims placed below the horizontal jambs.
- Make sure the window is plumb and level and adjust the shims if necessary.
Safety: When handling glass, always wear hand and eye protection to avoid injury caused by broken glass.
- Use a circular saw adjusted so that the blade depth equals the thickness of the siding.
- Start the cut with the toe of the saw plate on the siding, but with the blade and heel of the plate above the surface.
- Slide the saw guard back, start the saw, and ease the blade into the wood.
- To avoid splintering, stop before the corner.
- Complete the corner cuts with a sharp chisel.
- On a level window with brick mold, tack the window in place by pre-drilling and then driving 16d casing nails partway into the top corners of the moulding.
- If the window is uneven, correct it by shimming below the side jambs and then tacking in place.
- Measure the diagonals of the window.
- If they are equal, the window is square. If not, adjust the shims until the window is square. Always double-check that the window is level and square after you adjust the shims.
- If the window has a brick mold, pre-drill holes in it and drive 16d nails through it and into the framing.
- If the window has a nailing fin, nail through it into the framing.
- In either case, start at the corners and space the remaining nails as recommended by the manufacturer.
- Drive all nail heads below the wood surface with a nail set.