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Community and Q&A

Choosing Window Trim Style

user-7601308 | Posted in General Questions on

Hello, is there any difference aside from aesthetics when deciding between picture frame window trim and window trim with a stool and drip groove? this is for exterior trim. I am repurposing some windows that came out of another house and the jambs are wooden. they used to have stools with the drip groove underneath, but most were damaged when they were taken out of the previous home. It seems to me it would be easier to just remove the remaining stools and then do picture frame trim all around. My R.O. sills are all sloped and flashed with FlexWrap. The bottom of the jambs seem to also have a slight slope to them. Am I correct that either option is just a “make-up” choice and should have no effect on my water drainage?

should the jambs have positive slope like the Rough openings?


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  1. Expert Member
    Michael Maines | | #1

    Forrest, the decision is mostly an aesthetic one. Some people prefer the planar look of picture-framed exterior casing and if installed correctly it should work just fine. That includes having a rain screen gap and a sill pan that drains; the vast majority of rotten walls I've seen under windows are with picture-framed trim applied tight to the WRB.

    I usually prefer using an exterior sill extension ("stools" are on the interior) because it helps kick water away from the wall at a vulnerable location, and because I prefer the shadow line it provides. You can include a rabbet for the siding to tuck into and you can add a drip kerf, both of which help keep water out of the wall.

  2. Patrick_OSullivan | | #2

    The form comes from the function. Those extended sills are helpful for keeping water away from vulnerable areas. This was a necessity in older structures, and still helpful today even when you've employed good lapping and flashing techniques.

    In some house styles (e.g. colonial), picture frame will just look wrong, but that doesn't mean it hasn't become very common.

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