A New Window in One Day

It can be intimidating, but replacing a window is just a series of simple steps

It’s easier than you think! We’ll walk you through the steps.

The kitchen in our new house featured a garden window that was stealing useful cabinet and countertop space. We didn’t like its exterior look either, and ultimately my wife, Steph, decided to take the lead on replacing it. Doing it herself saved our family about $1,200, and with my help she got it done in just a day. At first she thought she was biting off more than she could chew, but she quickly realized that—like most carpentry jobs—window replacement is just a matter of following simple steps. Here’s how to do it:

1 REMOVE THE TRIM

Cut the caulk around the trim and the window. Pry the trim away from the window and the siding. Remove the trim from the inside of the house as well.

2 PULL OUT THE OLD WINDOW

Remove the screws or nails that hold the window in the opening. If the window still doesn’t budge, there may be foam, more caulk or hidden screws keeping it in place. Work a reciprocating saw blade between the window and the framing and cut around the window, then wiggle the window out of the opening.

3 FRAME THE NEW ROUGH OPENING

The new rough opening needs to be 1 in. wider and 1 in. taller than the new window. That allows space for leveling the window and insulating around it. We first raised and leveled the sill and added cripple studs. Then we added trimmer studs to make the rough opening the size we needed. Make sure the trimmers are plumb and there’s enough blocking for sheathing.

4 PATCH IN THE SHEATHING

Cover the framing with exteriorrated plywood or OSB. Our job required only a 2 x 4-ft. sheet of 3/4-in. CDX plywood. Steph cut it to size and screwed it into the framing with 2-in. coated screws. Then she capped the sill by nailing on a piece of cedar siding ( Photo

5), giving it an outward slope. If any water gets in, the slope will send it back out.

5 TUCK IN TAR PAPER

We used tar paper as a water-resistant barrier (WRB). Newer houses might have house wrap material, which will work the same way. Start at the bottom and overlap the existing WRB. Then cover the sides, followed by the top, always overlapping the previous layer and tucking the WRB underneath the siding as best you can.

6 FORM THE WINDOW PAN

The window pan protects wood from any water that might enter around the window. Cut flexible flashing tape 12 in. wider than the window opening, peel off the backing and lay the tape on the sill without stretching it. Starting from the middle, press the tape into the corners then up the sides. Fold it over the sill and stretch the tape around the corner. Many window installers don’t cover the side or top corners with flashing tape, but I always add the extra layer of protection. I wrap 4-in.-wide flashing tape over the side corners, then the top. When all the tape is on, roll over it with a J-roller.

7 APPLY SEALANT TO THE WINDOW

To make the connection watertight, apply a continuous bead of sealant along the side and top flanges. Be sure the bead goes right over the nail holes; penetrations through the tape must be sealed well. Don’t seal the bottom flange; if water gets in, it must have a way out.

8 PLACE THE WINDOW

Rest the bottom of the window on the sill, then tilt the window up and into place. You’ll need a helper waiting inside to center the window. Next, the helper will raise the window with a few shims and adjust them to make sure the bottom of the window is level. When it’s level and centered, drive a nail in the very bottom hole on each side flange.

9 PLUMB AND SQUARE THE WINDOW

Hold the window in place with a few sets of shims on both sides of the window, a pair that holds the top and one toward the bottom. Adjust the shims so the sides of the window are plumb. Once the bottom is level and the sides are plumb, drive a nail into the top hole of each side flange. The real test is how the window operates; don’t nail it off until it operates smoothly.

10 NAIL THE FLANGE

When you’ve centered the window and it’s level and plumb and operates smoothly, drive nails in all the holes on the top and sides. Don’t nail the bottom flange. Then install the drip cap that came with the window.

11 COVER NAIL PENETRATIONS

As an added measure against water intrusion, cover nails in the flange with flashing tape. Start with the sides and extend the tape a few inches past the bottom and top nail flanges. Then cover the top flange, making sure it overlaps the tape covering the sides.

12 INSTALL Z-FLASHING AND TRIM

Install Z-flashing above the top piece of trim. It should be cut to the same length and tucked under the water-resistant barrier (tar paper or house wrap) and will shed water over the trim. Then install the trim using coated trim screws.

13 REPLACE THE SIDING

Our siding is double-course cedar shakes, which we were able to match easily. Caulk around the window and trim using a highquality exterior sealant. Then paint the siding.