How much height to add to RO for a sloped sill?
Hi all, new user here. I’m a owner/builder with an eagerness to learn.
We’re building a workshop/studio/garage in N. Florida with Thermasteel SIPs.
I’ve been deep diving on building science youtubes and wherever I can read more in my spare time leading up to this point.
My question is about the use of a sloped sill that I’ve discovered while watching the Build Show content and others (WKD Construction) who employ this technique.
Since we’re using prefabricated panels and flangeless windows, I’m stuck on how much room in my rough opening I should spec for the addition of the sloped sill (back dam, sloped siding cut to length of sill (5/8″?) and reverse shim placed on top of that slope for the “level” platform for the european style window unit to rest upon.
If it’s, say, a 5/8″ sloped piece, then I assume flipping the material for the level platform would mean about an inch and 1/4 total? (5/8 plus 5/8?).
How common is this sloped sill practice?
Thoughts? Thanks in advance!
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Replies
The pitched sill is a great detail. Your drawing shows the 5/8" wedge (clapboard or shim) with a similar wedge used to level out the first slope. The total height of the material would be roughly 5/8" (thickest point to thinnest point). It will probably end up slightly more. I would say between 3/4" and 7/8" extra for the buildup of material would be enough. Of course, the RO requirement for the window would be added to the sloped sill material.
Hope this helps,
Randy
Much appreciated Randy. I think the 3/4 to 7/8" makes sense, being that there will be a little additional height cumulatively with the material built up as you write. And yes, I'm working with the manufacturer for the RO they require and then adding this extra space so I can make an effective sloped sill assembly similar to the drawing.