Ask Jon Eakes

Last Updated: Sunday, February 15th, 2004, Created: Sunday, February 15th, 2004

Just how do you install windows properly?

The reality is that there is not just one good way to install windows, but there are certain principles that must be taken care of with any installation to prevent cold air or water leakage later. We followed one good installation with Brian in Victoria B.C. where window leakage has often been a problem.

Basically a window installation must shed most of the water with the siding, what does get through someday is keep away from the wood and directed downward with a drainage path that positively drains outdoors -- the wall portion between the sash and the frame is insulated and sealed air tight on the inside. Here are the details of one way to accomplish that as we follow Brian with my camera.

1- Milled and pre primed 2x6 for the rough sill provides positive drainage outwards.

2- Row of building paper under the window -- building paper is always put on in shingle fashion, overlapping to direct water away from the wall.

3- Primer on building paper, wall and sill to assure permanent adhesion with the peel & stick to come. Long term adhesion of peel & stick can be a hidden problem.

4- Peel & Stick applied to lower portion of window to receive and redirect outwards any behind-the-siding water flow. Note they bring the peel & stick into the house beyond the window frame to avoid the black sealant, which is under the blue surface, from bleeding into the white finish caulking. Notice careful and total sealing of corner joints -- three layers to really seal the corner and not leave a little gap at the horizontal-vertical-wall junction.

5- Building paper 'shingled' over the rest of the opening. Any water that penetrates the siding is directed down to the waterproof lower area and shed outwards. They don't use the peel & stick here in order to allow any moisture in the framing to move through the building paper and out.

6- Spaced shims provide complete horizontal support for the window over the tapered sill plate and a drainage pathway outward.

7- Sticky adhesive is placed over the window frame to catch and seal edge of building paper to the window frame just prior to the installation of siding.

8- After insulating between the window and the house framing, foam backing rod is stuffed around the frame, to be covered with caulking and the sill plate put into the wet caulking to seal it to the frame.

9- The 2007 code requirement in Canada now require end dams on all header flashings over windows and doors. For details on how to do that, follow the link to window header end dam jig.

"Window Wise"

is a Canadian program dedicated to good window installations. Their site is worth a visit.

Keywords: Air Barriers, Doors, Installation, Leaking, Moisture, Rain Screen, Rot, Sealing, Techniques, Windows

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