So I have a cinder block block that is about 4 feet high.in which I will be putting a framed 8' wall. I will be using a 2x6 sill plate PT. How much space do I leave for the sheathing. It's an exterior wall. Also once the sill.plate is down, can I put.my studs on it or so I need an additional plate.

  • Hello, and welcome to Home Improvement. It's a little hard to understand what you mean; would you add a diagram to your question? And, you should probably take our tour so you'll know how best to participate here. Sep 28 '19 at 1:08
  • Are you installing floor joists on this cinder block wall and then installing an 8’ wall on top of that??? Is the 4’ high wall part of the foundation, so there is a crawl space behind this wall? Or, is this 4’ high block wall part of a 12’ tall wall system??
    – Lee Sam
    Sep 28 '19 at 7:36

It's recommended (and possibly required by building code) to add a sill seal below your sill plate. These are usually inexpensive rolls of foam, and serve to protect the sill plate from rot. The sill plate also needs to be properly anchored to the foundation, generally every 4ft is required. As far as a second sill plate, this isn't required.

  • so what any foundation over 16' long is going to require a double sill plate? Sep 28 '19 at 1:47
  • This was my guess based on observation in my own home, but based on follow-up googling, it seems that double sill plates aren't terribly common. My new guess is that the carpenter who built this house just wanted it to last, and went over the top. The ICC website is not very mobile-friendly so I'm not going through the trouble of reading it, but you can find their requirements there.
    – Nate
    Sep 28 '19 at 2:28
  • Yeah no requirement for double sills. Each sill plate needs to be bolted within a small distance of the end so you need more foundation bolts but joins are fine. Structurally this makes sense, studs bearing down on a sill don't care if there is a join, even if you put an enormous amount of weight on a sill and to the side was a join and you were able to cause that portion of the sill to lift up it just wouldn't affect anything. Walls are typically built and pushed up so that usually dictates the sill length, how many people are pushing the wall up and the weight of that wall. Sep 28 '19 at 2:38
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    I upvoted because with the information provided this answer is absolute correct, foam seal keeps the plate from rotting out due to moisture, anchor bolts vary in spacing based on seismic zone. The bottom plate is usually flush or slightly proud or outside to allow for metal flashing. Good answer +
    – Ed Beal
    Sep 29 '19 at 0:56

Single bottom plate, double top plate. Wall sheathing is typically 7/16" thick.

Current code in my area requires 2" rigid foam insulation on the exterior of the block wall. Some builders have been using 2x8 walls so they can overhang it over the foundation 1-9/16" so the face of the wall sheathing is flush with the face of the foam. I think it's silly, but that's what they're doing.

  • Are you saying there is a 1-9/16 over hang? That is a huge gap?
    – Ed Beal
    Sep 29 '19 at 0:58

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