Hello:
Well, my buddy, who will be helping me build my house, just saw the double-wall framing detail drawings and, he is not happy. He believes that framing such walls will be too difficult and take way too much time, mainly the window & door openings.

Has anyone here actually framed a house with double walls? Is it really that much more difficult?

what is his concern? the 2nd wall is the same as an interior partition; lining up the windows openings is just a matter of laying out the studs correctly on the plate; you can line up the plates of the two walls side by side and lay them out together. In the picture, I'm assuming you build the outside wall first and push it over the floor onto the foundation &stand it up - that could have some difficulty, but is doable.

Of course it does take more time - and money,but costs less over the long term & is much more comfortable.

Thanks Bob. :)

His major concern is bracing the outer-wall components while installing them.

Because we are building on bedrock, where the soil is only a foot or so deep, he says that we will need to brace to the sub-floor and that the outer-wall braces will interfere with erecting the inner-wall.

I was thinking that we would start at a corner and install one section of each outer-wall and then brace them across the top-plates with a 2x4 at 45 degrees. Then start installing the next sections to the next corner, using temporary braces to the sub-floor until we can install the next right-angle wall and brace that at the top-plate, and so on.

Does this make sense?

We will be framing each wall in 'manageable sections' as there will be only 2 of us doing it.

Rob.

Although I was living onsite during our house project, there were too many gaps in time when I wasn't actually watching, being engaged in other things, so that I didn't see much of the erection of the interior wall frames, although I have pictures of some of them lying on the floor platform. One way of bracing the outer wall to the platform is with braces located between studs of the inner frame, so that the inner frame is assembled and stood up around the braces. Anyway, at some point I asked the framers (crew of four) how long they figured it took them to assemble and erect the inner frame (182 linear feet for the upper level). They said perhaps a day and a half total. I get the feeling that your buddy, who obviously hasn't done a double wall before, is shying awy from from what he doesn't know. A great many double wall houses have been built over the years. The time and expense for the second wall isn't really all that much in the greater scheme of things.

I've done double wall where the outer wall is the structural one so we haven't had that issue, but I like this method better. So however you can do it.... your method of bracing the corners sounds good. Since you'll have short wall sections, the previous one can be fastened to the next one, so the only issue will be doing the first one. Another alternative is to brace it to a tree or to a 2x4 stake pounded into the ground - there won't be any weight on it so you just need it to sit there until it's fastened to the inner walls.

Thanks Dick & Bob. :)

I was planning to frame both walls and then install the hip-roof framing, is that the way to do it?

My buddy suggested to sheath the outer-wall sections, on the sub-floor, before erecting them - what do you think. Personally, I don't agree but I have been wrong before. I think that sheathing them on the sub-floor will a) make them even more unwieldy, and, b) make it difficult to make them as air-tight as possible. (Zip Wall Panels)

If we don't sheath the outer-walls on the sub-floor, should they be sheathed before framing the roof?

(I will be buying the hip-roof trusses from a truss manufacturer, I won't be building them myself.)

Thanks,

Rob.

sheathing them first makes them heavier, but it's a lot easier & much faster to sheath them on the ground than doing it after they're up. Just do shorter walls if you need to. Be sure to leave 1-1/2" of sheathing hanging below the wall to nail to the sill plate.

make sure all your walls are well braced before setting the trusses. I assume you're getting a crane to lift them?

Before sheathing the walls on the floor, be sure to do a quick check to make sure they are square.

Yes, I'd sheath on the floor. If you use wall jacks (Proctors or equivalent), the pair of you can erect longer wall sections easily, and have fewer joints. The jacks also provide temporary bracing until you nail on the wood braces, which saves having one of you wrestle with holding a heavy section upright on that windy day while the other scrambles to nail something to it.

You'll need something to tie the tops of those walls together anyway, and the local BI may insist on a 3/4" plywood or OSB plate for firestopping reasons anyway, so I'd get that on while the area is accessible, before setting trusses. In some designs, that top tie plate is left out, and the cellulose loaded dense packed from the attic space, ultimately covered with the layer of cellulose in the attic. The idea of that is so that if there should be any settling, despite the dense packing, the attic load above the wall will just settle to keep the wall cavity filled. I think it may have been Robert Riversong who once described doing it that way in a post here or elsewhere.

Thanks Bob, Alton & Dick, I appreciate your help.

I'll look into "wall jacks" - who knew!?!? :)

Originally, I was going to insulate with cellulose, and would want the space between the double-walls open to the attic, but now I think that I will be using Roxul Comfortbatts, as suggested by Liebler, as it is a more DIY product.

Although I don't like the 'thermal bridge' aspect to tying the top-plates together, other than with the roof trusses, I'll do it it the BI insists.

Rob.

Hello:

The 'mutineer' has requested that I make this post.

His question is: 'How much less energy-efficient would the house be, if the walls and floor were built as per the drawing below?"

My question is: "Is there an accurate way to determine the answer to his question?"

I cannot disagree that, constructing the house as the drawing shows, would be a lot less difficult.



You thoughts would be appreciated.

Rob.

I don't know, but my guess would be "some, not much" perhaps others have more detailed information. However, a couple of considerations: I'd (almost) line up the studs - of you are doing dense packed cellulose (please don't say fiberglass) so they'll need to staple fabric to the stud sides to form a deep stud bay. My electrician wants the studs offset by at least 1-1/2" so he can staple wires to the inside face of the outside studs to save drilling. If they're lined up he cannot do that. Second, I'd recommend spray foam rather than sheet goods at the rim joist to help air seal the area and the sill plate.

Also, Conservation Technology sells EDPM building gaskets that you can use between the foundation and the sill plate and under the exterior walls. The pink/yellow/blue foam stuff everyone uses is useless.

Thanks Bob. :)

Although this drawing does not show it, the construction drawings (mine) do have 16" OC studding on both walls - now, I have to move one set 1.5" - thanks a million for that tip!

Also, I will be using spray foam on the rim joist, I just don't know how to draw it using Sketchup.

I'll look into a source for EDPM building gaskets here in Montreal. Maybe I can drive to Plattsburgh NY to buy them or maybe Burlington VT.

I guess you are not a big believer in Roxul ComfortBatts. (I think you have mentioned that to me before) The 'jury is still out' on that one, too many conflicting thoughts.

Rob.

conservationtechnology.com will ups them within a few days. excellent service.

Hi Bob:

If I am using Zip Wall Panels for my sheathing, do I use gaskets on any or all of the exterior wall studs, under the panels?
Thanks,
Rob.

Yes. the zip sheathing is designed to make the outer surface of the wall airtight, but it does nothing for othher gaps such as the one between the sill plate and founation. An argument could be made that the gap between the walls and floor are covered by the zip, but the cost is minor and that is a common place for leaks.

Isnt the only real difference between your first and second wall options the subfloor extending to the exterior and an extra bottom plate?

I don't know the cost of the epdm gaskets, but when we spray foam the sill boxes we encapsulate the mudsill to the foundation in my opinion negating the need for a higher cost material than standard foam, the flexibility aspect of the gasket is nice though.

Thanks Bob & greentree. :)

I guess I'll go with the mutineer's drawing. If I don't, I'll be building it by myself.

Rob.

You obviously have considerably more thermal transfer on the Sill plate and floor joists with the new system. If you are planning on an exterior Sheet insulation it should be considerably mitigated.

The mutineers have agreed to this wall:





The details of which can be seen at: https://docs.google.com/file/d/0B7b9_F7Z3_0pT3JjeHdlQnJ2TEU/edit?usp=sharing

From outside to inside:

1. Horizontal siding
2. Vertical 1"x3" strapping
3. 2" Rigid foam - R-10
   
4. Zip Wall Panels
5. 2"x8" wall framing @ 16" OC filled with 7 1/4" Roxul ComfortBatts R-28
   
6. 2"x4" horizontal strapping @ 24" OC filled with 3 1/2" Roxul ComfortBatts R-14
7. 6 mil vapour barrier
8. 1/2" Drywall.

Notes:

1. The exterior of the foundation will have 2" of R-10 rigid foam and the rim joist will be spray foamed on the inside.
2. Sill, rim and drywall gaskets will be used.