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Last Updated: Friday, April 20th, 2012, Created: Monday, January 15th, 2001

Proper window installation

In this segment we went step by step through a proper window installation.

The critical details:

A window must be plumb, level and square.

A window must be properly supported by shims in the right places.

A header flashing must be installed above a window that has a minimum 6 degree slope to the outside and includes end dams to prevent water from entering the window area at the top.

Something must be installed in the window-to-house space (between the rough opening and the window frame) that acts as a "drainage layer" -- the furthermost point that moisture that gets past the flashings and caulking can go before it is redirected and drained outdoors. This drainage layer is a critical new element in cold climate window installations, an acknowledgement of the reality that water will probably get past the outer layers of protection, and that water must not be allowed into the walls. Window frames that counted on the exterior caulking are the greatest causes of water damage in walls below windows.

This same cavity must be completely insulated to keep the window frame warm.

This same cavity must be sealed off air tight on the inside of the house to prevent household moisture from migrating into the wall by air currents moving around the window trim.

Keywords: Air Barriers, Caulking, Damage, Drainage, Flashings, Frame, House, Installation, Insulation, Levels, Moisture, Moisture Barrier, Moving, Outdoors, Protection, Shim, Steps, Trim, Vapour Barrier, Walls, Water, Windows

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