When most folks hear the term window trim, they think of beautiful interior casing and sill details around a living-room window. While the interior trim is traditionally a place to showcase finish carpentry, most windows also have trim on the outside, which plays a part in defending the windows and the home against the elements. So proper execution and installation of exterior window trim is probably more important than that of the flashier interior trim and is something just about every house carpenter will be asked to do on a regular basis.

Wood was typically used as exterior trim on houses for centuries, but wood trim demands regular care to keep it protected from exposure to the elements. In the last couple of decades, synthetic materials have taken over as a more durable choice for exterior trim, and I have switched over to these materials almost entirely. Synthetic trim materials come as flat stock or in conventional stock profiles. For the trim in the photos in this article, I used standard PVC brickmold for the jamb and head casing. I fabricated my own sills from PVC flat stock

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