Innie Door Sill Pan
Hey all. We have all our 3in polyiso exterior insulation up. We’ve installed all our windows as outies but want to install our doors as innies. We have 4in of insulation around the perimeter of our slab foundation. I’m trying to figure out the best way to do a sill pan for the exterior doors that will also protect the foundation insulation from being stepped on.
1. I’m wondering what the best type of sill pan would be? I have ZIP stretch tape but I’m wondering if it might be better to do a metal sill pan, I’m just not sure how well ZIP will stick to concrete.
2. I also want to include a slope, I was thinking a piece of beveled siding, would that go under or over the sill pan?
3. To protect the foundation insulation I was thinking about using diamond plate steel to extend the threshold out past the foam, I saw a picture where someone did that on this forum. Or is there be an easier method?
4. I already have a PVC door jamb for 2×6 construction. For extension jambs, can I use lumber or should I stick with PVC? What would be the best way to attach those? Pocket screws or just through the face of the jamb?
Thanks in advance!
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Replies
CB,
You may find this article useful:
https://www.greenbuildingadvisor.com/article/how-to-install-doors-in-thick-walls
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Hey Malcom,
There are good ideas there but I would like to avoid cutting into the slab to create the recess. Is there another option for a sloped sill and/or back dam in this case?
Also in your detail, what holds the vertical foam onto the concrete slab? Is it screwed or glued to it?
CB,
Michael Maines, who is the author of that article (and posts here) is probably best placed to answer your questions.
Bumping. Hoping to get some more ideas for this.
Cottagebuilder, if the slab is already in place your options are more limited, but I would (and have) go with something like my two slab options, just without the recess and thermal break. You can either run heavy-gauge metal flashing, a Pemko sill (https://www.pemko.com/en/products/thesholds-ramps/commercial-thresholds) or a piece of stone or cast concrete over the foam as a sill extension. I've seen diamond plate used for this and with certain architectural styles it can look great. With more traditional designs it won't look right to most people. You may or may not need to add support at the outer edge, depending on the foam density and how well it's adhered to the concrete.
To limit thermal bridging through the door sill you could add a high-psi strip of foam under the sill, but that can be hard to get, especially in small quantities, and would likely only save you a few dollars a year in energy costs. It would increase resistance to mold resulting from cold interior surfaces. I'll attach my original drawing that GBA's art staff spruced up for my article.
I would NOT use a metal sill pan if you're in a cold climate; it will readily conduct heat. The last time I used one, made of copper, I saw heavy frost on the interior and realized just how dumb that was. There are a multitude of options for membrane and fluid-applied pans and they will all work. I would turn it up against the inside of the sill and run a piece of trim across to hold it in place.
If you want to include a slope, I would place a solid clapboard or similar under the sill pan, and plastic or rot-resistant wood wedges along the top to create a level surface for the door. It won't meet manufacturer instructions which require a solid substrate, so don't expect a warranty to be honored.
Extension jambs can be wood or plastic. I avoid plastic as much as I can so I would use rot-resistant wood. I also do my best to always include roof overhangs at doors, which makes a huge difference in how much stormwater they see. I'd probably pocket-screw or Domino them together before installation, but it's about the same amount of work to install them in place--just use a high-quality glue or sealant at the joint.
Hey Michael,
It’s funny you brought up the copper sill pan, we were down at the lumber yard today and asked them for input and they said to use lead or copper for the sill pan. I had read that that’s a bad idea to do in cold climates so luckily we didn’t buy any copper.
I think I’ll plan to use stretch tape and do the end dam like you mentioned with the trim.
I’ll try to find some cedar locally to use for the extension jambs.
Thanks for help!