At Arlington, we run a small three-man shop, cutting one frame at a time. Over the years, our frames have evolved in a different direction than most: toward old time mortise & tenon joinery, not away from it.
Our highly gifted craftsmen have carefully honed their skills until they can quickly and efficiently cut even the most sophisticated joinery as a matter of course. This method creates a much more satisfying frame to design, cut, and erect – not to mention the enjoyment of standing inside the finished home with the proud owners.
It turns out that this method is surprisingly no more expensive. There is no need to buy any hardware, or have metal plates made up in a machine shop to be wrestled into place on raising day. There are no timbers fitted into shallow housings and fastened in place by hidden screws, toenailed from the back side.
All of the layout and cutting of the more complex joints is done on the sawhorses at once. It may take 20 minutes to carve a nice tenon for that mortise, ready for a wooden peg to be tapped in on the big day of the raising. We leave the screw guns for the drywallers.
Sixteen years ago we had several of our joints tested by TUNS (Technical University of Nova Scotia, now part of Dalhousie University). The results were surprising, to say the least, with our connections far exceeding any expectations. We have found no reason to change to more “modern” methods.
No beam left behind
The other main difference in our timber frames is the fact that we build them to stand alone. They don’t require structural panels, or S.I.P.S. Of course, panels work fine on our structures, and we have no problem with them, but our frames just don’t need them, especially in the areas of dormers and open valleys. The dormers and valleys have a nailing surface everywhere you’ll need one for the 3/4” v-groove or other sheathing material. The general contractor doesn’t have to figure out how he’s going to frame a dormer in the great big hole we might otherwise have left for it; the dormer is ready for sheathing and the beautiful timber frame joinery will be visible from the inside for the owner to enjoy.
Our enclosure method
The roof is “built up” on site with materials from local suppliers. Over the frame, V-groove sheathing, or the less modern tongue & groove (without the “V” ), is nailed over the timber rafters. This is covered with vapor barrier in an unbroken envelope, all seams taped, with a couple of feet hanging down to later be joined to the vapor barrier on the walls.
Next, rigid foam is applied in two staggered layers. It is held down with horizontal 2x4s on 16’ centers, on top, nailed through the foam and into the timber rafters. On the gables the 2x4s are run out past to be chalklined and cut off to form the overhang. The foam is installed in an unbroken envelope, not pieced between other members like pink insulation in a stud wall. Some foams, like Quick-Therm, have a foil vapour barrier with handy “sticky tape” overhangs to make an easy seal.
Another layer of 2×4’s are installed vertically, with the tails running out to form the eave overhang. This layer is much easier to put on as there now is handy 2×4 strapping to walk on.
The plywood or board sheathing is applied, then shingles, or steel roofing. If the latter is chosen, the sheathing can be foregone.
A roof insulated this way will perform much better than R-value “rules” would indicate. The double air space created can breathe easily in all directions; around valleys and hips, from the soffit vents up to the ridge vents.
This air space seems to be the secret. The radiant floor in the Newcomb (link) is heated by an everyday electric 60-gallon hot water heater, bought new for $300.
It turns out that this roof system can be built more cheaply than factory-made roof panels, even with the extra time it takes to install. As all work is done on site, there are no unhappy surprises.
We use an “out fill” stud system on the walls, with either 2x6s or 2x4s. The contractor builds sections of walls the length of each bay which butt together on the back of the posts. These sections are framed like a normal wall with window and door openings, except there is no need for 2×10 headers, just 2×6 to give something solid for the inside and outside trim. Remember, the timberframe is carrying all of the weight. There is also no need for built up corners (drywall corners), so in the end, you use much less 2x stock than a conventional stud wall. These wall sections are often built on the floor, and boomed off out of the way by us when we arrive with the frame.
The first step is to attach drywall to the outside of the frame. If it is a windy day, one wall is done at a time. The drywall is screwed to all of the timbers. This keeps it tight even after the timbers shrink. Next, vapor barrier is stapled to the outside of the frame, wrapping around the house and joining back at the beginning, and taped. Remember the 2’ of vapor barrier hanging down from the roof? That is now taped to the wall barrier. You now have a complete one piece vapor barrier over the whole house, in one step.
Next, the stud wall sections are installed from the outside and spiked to the frame. Inside, the drywall is now screwed to the studs, keeping away from studs that are less than 6” from a beam. This insures that the drywall will curve slightly as the beams shrink over time, leaving no gap.
The 2×6 walls can be filled with pink, or with blown in cellulose for a bit better performance. If more insulation is required, we often add rigid foam to the outside in an unbroken envelope, held on with 1×3 strapping on the outside to attach siding, while creating the important air space.
In the last few years, many clients have been using 2×4 walls with no pink, and installing the vapor barrier over the outside sheathing. Many are using Quick-Therm insulation as it has its own foil barrier.
The manufacturers claim that this system, with the proper air space, will perform at the equivalent of R27 in a pink-filled stud wall.
This product has been around for a few years. There has been a little controversy about the R-value claims. So far, the only critics I have heard are competitors. I haven’t heard of an unhappy client.