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| The southeast corner of the main floor after installation of sheathing. The plywood extends right to the top of the walls for racking, even though the drop-ceiling that will be installed under the trusses will bring the air barrier down two feet from the top of these [10'] walls. When insulating above the ceiling, the extra plywood will serve to contain the loose fill cellulose around the perimeter of the attic. |
Tuesday, April 24, 2012
Sheathing the main floor walls.
Just a quick post on sheathing the walls. There is not much to say on the subject except that I used the same 1/2" t&g plywood on the walls as I did on the roof. The cost for this plywood over square edge is marginal and it makes for very robust wall sheathing. I'm sure it's been mentioned in several other places, but I installed the plywood on the inside face of the exterior walls for racking resistance, air barrier and vapour retarder. The seams will be taped at a later date to complete the air barrier.
Pretty Noose - Soundgarden
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Ive enjoyed reading your blog. I really like the thought put into the wall system. As I study your wall details, I notice that you do not use vapor barrier, but plywood on the inside of the wall. Also, it appears you nailed tamarack siding directly to your outside wall studs without any exterior sheathing. Do I read correctly? I very much like the idea of not building a wall that consists of insulation sandwiched between two layers of plastic. It seems to me that this system allows the wall to breathe a little. Do you have a source for tamarack siding? I had to look it up because I have never encountered this material in Alberta, although we have lots of tamarack trees.
ReplyDeleteHi Andrew,
ReplyDeleteI'm glad you've been enjoying my blog. I haven't added any new material in some time, but I'm still hoping I'll find time to bring it back to life on of these days.
To answer you questions, it seems you have correctly understood my approach. Like you I am wary of impermeable materials in envelope assemblies. The plywood functions as an effective and code-compliant vapour retarder here in Ontario (your milage may vary), and having it located so close to the interior of the assembly, it stays warm and dry (no worries about condensation).
On the exterior side, as you mentioned, I omitted exterior sheathing because it would have been overkill, but still wanted a tough exterior shell. The tamarack siding I used was planed quite thick (a full 1" at it's thickest edge) so even without sheathing behind it, it is very robust. Tamarack siding isn't very common here either, but there's a mill not far away where they've been making it for some time now. Not sure, but I think Tamarack is difficult to process into a finished product because the trees themselves are prone to "wind-shake" and good saw-logs often contain big cracks hidden under the bark...
Anyway, one thing to keep in mind with this approach is that there is no nail-base behind the siding, so some though has to be given to how the siding will fasten around windows, at corners etc. A little blocking here and there behind the Typar was all I needed to make sure I had good nailing.
Here is a link to the mill where I got my siding (and now also baseboard, casing etc.):
ReplyDeletehttp://www.precisionwooddesign.com/
Yes, and balloon framing pass the rim joist makes great sense as well. I notice that the studs on your inside and outside walls line up and are gusseted together. I suppose that gusset is necessary because that outer wall runs continuous. I was thinking of staggering the studs (2x4), with an airspace in between (2 layers of R12). I see that you spaced the two wall far enough apart to add a third layer of insulation. Thanks for the link to that mill. I will check them out.
ReplyDeleteLiving anywhere in Alberta, I'd highly recommend framing the cavity wide enough to get something close to R40 in the walls. Now that this house is closed in and running, it really is amazing how little effort it takes to keep the place warm in winter. If you're near forest at all, the Roxul insulation I used is essentially fireproof.
DeleteYeah, I will look into that. I had not considered mineral wool in place of fiberglass batt insulation. I have learned a lot from your site. Thanks again for sharing.
ReplyDelete