Framing the main floor walls.

I'm skipping ahead with this post, as I will probably do now and again. This will be the first post that covers some of the practical aspects of air sealing this house. Just a reminder that all these "practical aspects of air sealing" are the application of what I have laid out in the "Details" section of this blog. Please note, this post doesn't cover the "building out" of the walls (ie: framing the truss wall) - that will be happening later. It's worth mentioning at this point that one big advantage I've found with the truss wall approach to framing the house is that since the exterior truss framing is all non-load bearing, a pretty straight line can be made to getting the roof on. It's just like platform framing any conventional house but with some added air sealing details. The truss wall can be "built out" at any time.

Some readers may be wondering why I am skipping past the framing and air sealing of the basement walls? Well, it's because I forgot to take photos when the basement was being framed and since the procedure is almost the same (a few extra steps involved with the basement), I thought I'd start here.

As I already alluded, framing the main floor walls was a fairly conventional exercise. The most important thing to remember is to ensure the proper application of the air-stop tape prior to lifting the wall. In this case, the air sealing strategy demands that air-stop tape be applied to the bottom plate during framing since it will be impossible to install properly after the walls are erected. Further taping of the sheathing can proceed at any later time. The procedure was as follows:

• Each wall section was nailed together on the floor deck then squared and braced.
• The bottom plate of each wall section was shimmed off the floor using 2x4 off-cuts, so as to provide work space for taping.
• Air-stop tape (in this case 3M All-weather flashing tape 8067) was applied to the bottom pate.
• The wall was lifted into position and braced.
• After all wall sections were in place, plumbed and straightened, 1/2" plywood sheathing was applied to the interior side of the stud wall.
• The air-stop tape at the bottom plates was "connected" to the plywood sheathing.

Frame a wall section.

After squaring, brace the exterior side with 2x4s - make your life easier
by nailing the braces on with duplex "forming" nails. Notice that since the
sheathing will be on the interior side, the header over that window opening
is flush with the inside of the wall so that the sheathing can be nailed to it.

Position the wall section so that it's near where you want it to be lifted up
(notice my chalk line in the foreground) then shim the bottom plate off the
 deck with scrap 2x4.

Apply the air-stop tape to the bottom plate. The 4" 8067 has a split backing
which makes the application easy. Peel the backing from one half of the tape
and apply it to the interior edge of the bottom plate, leaving the other half
of the backing on the tape. Later, this "flap" will tie to the plywood sheathing.

Before lifting the wall section into position, tuck the unused half of the
tape under the wall. It is critical to ensure that the unused "flap" of tape is
accessible and not pinned under the bottom plate.

When lifting a wall section and moving it into position, make an effort to avoid excessive dragging that may damage the tape where it is adhered to the underside of the bottom plate. Never having tried other brands of air-stop tape (Siga or Pro Clima for example) I cannot make any comparisons but I can say that the 3M 8067 is an extremely durable product that stands up well to job-site abuse. The 8067 does not tear easily and if punctured can be easily patched with a small piece of the same tape. After the main floor walls were erected, it was about three weeks before I installed the first (bottom) row of sheathing. During that three week period, the "flap" of 8067, with its backing still on, was left exposed to the elements and was rained on several times with no apparent effect on the tape's (aggressive) adhesive quality. It's quite impressive stuff, really.

In general I find it easiest to pull the backing off a couple of feet at a
time. Exposing too much adhesive at once can make for a lot of trouble -
especially if there is a wind blowing.

The "flap" on the left is "untucked" while the "flap" on the right has been
"tucked".

Plywood sheathing is attached and the "flap" has been adhered to it. When
installing the bottom row of sheathing, shim it off the floor with 1/2"
plywood scraps. If the sheathing isn't shimmed off the floor, it will pinch
the "flap's" backing and make it very difficult to peel off.