ERV duct route through top and bottom plates?
I have never built a house that had ductwork. Our next house will have an ERV. I think I found the perfect location (close to outside wall for intake and exhaust, serviceable location, etc. This would be under the stairway landing. The only problem I’m having is I would need to run the supply ducts inside the walls of the stairway (bedrooms are on either side of landing–see attached drawing). These walls are not loadbearing. If I platform-frame them, the ducts would have to penetrate a bottom plate and a top plate, which seems too tight. The other choice would be to balloon-frame the staiway walls, but it sounds like the fireblocking needs to be at the level of each floor. Either way, it sounds like I need to get a 3.25″ rectangle width or a 4″ round duct through one or more 2x4s. Any suggestions? Thanks! (Climate zone 6B/7B–West Yellowstone, Montana)
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Replies
Ducts are routed though top and bottom plates all the time. For non load bearing wall, just cut the hole you need. Sometimes you need to put some support for drywall, this can be one of the mending plates or 1x2 metal trim angle.
Sometimes it is easier to build a 2x6 wall to be able to run round ducts.
To add to what Akos said, if your wall is running perpindicular to the joists, the joists will tend to pin the top plate in place so you won't have any flex of the wall where you cut the top plate for the duct.
If your wall is running parallel to the joists, you may need to put in some blocking to hold the top plate in place on either side of the cut, but you just need to tie it into the joist on either side of the cut.
A trick I've used that may work depending on exactly what you're doing and how much access you have, is to replace or sister the top plate with something "big" like a 2x8 or 2x10 laid "sideways". This lets you cut out notches or holes as needed but keeps the integrity of the top plate since the larger board "wraps around" the notch or hole. It's best to drill the corners of a large notch here so that you radius the corners of the notch for less stress, and less chance of splitting.
Bill
That will do the trick. Thanks a bunch!
Oval.