Thursday, July 4, 2013

Starting to look like a house!

Here's the north side of our new extension, showing the first sheathing board now installed, under the stepladder. One down, 25 or so to go. You can also see the Amish-bought polyiso insulation boards -- the shiny foil-covered things to the right.

Here's a detail of a let-in cross brace. These are 4 by 1 planed pine material, which no-one would consider a particularly strong board, but they only have to work in tension and compression, and make a triangle with the studs, so they're actually enormously strong and will in fact keep the entire building from "racking" like a house of cards. Racking is when the entire building leans over. Here in Maine, where high winds, particularly in fall, and heavy snow loads are both natural hazards, you can see lots of "racked" buildings, all of which were insufficiently braced. Ordinarily in a modern building the 4 by 8 foot sheathing boards would do the work of bracing, but ours will be weakened by heavy insulation.

Speaking of which, here's a detail of the wall 'sandwich' showing the 1.5 inch polyisocyanite insulation under the 7/16ths OSB sheathing. The lighter colored framing on the left is just regular planed 2 by 4 stuff that we'll use on the inside for the interior walls, in this case the bathroom wall. It knocks together much more quickly than the full-width hemlock, but lacks the shear strength we want. I can't believe that people build whole houses with this stuff, but up until recently nearly all houses will built using "nominal" planed 2 by 4s, which are actually 1.5 by 3.5 inches.

This insulation has a reflective exterior which works by reflecting radiant heat loss back into the building. It needs an air gap to work well. Here, we'll have a slightly loose fiberglass pack in these walls, because standard R19 fiberglass batt is only 5.5 inches, not 6. That should allow the radiant heat property to work well. It takes 3.5 inch screws to get through all that foam and the outer sheathing, but once they bite into the hemlock, they're not going anywhere.

Unfortunately, the reflective surface also works very well in full sun while you're cutting the boards to size, so I'm wishing for either a cloudy day or some shade. It can get quite uncomfortable with the extra heat and sun-dazzle, working with this foam board.

The Ernie seal of approval. He's perhaps a little confused by the notion that there's a whole new 'inside" space arriving for him to chase Flame in.

Here's a detail of a corner "post"where three 2 by 6 hemlock studs come together to make a strong corner, plus you can clearly see the backside of a let-in cross brace. The joints have to be nice tightly fitted for the brace to work at full strength, no big gaps. Mine are all nice and solid, which, considering this is the only "real" bit of carpentry in the whole building, makes it seem like a shame to cover them up! I use my lightest circular saw and a nice sharp Sheffield-made (of course!) carbon-steel framing chisel that Aimee bought me for a Christmas gift one time.

Now that was a good gift. I already had a set of traditional framing chisels, but they were blacksmith-made here in the US, not real Sheffield steel. You can easily tell the difference. The cruder chisels can't be pushed through the wood as easily by hand as the Sheffield tools can. They're a pleasure to work with.

Flame explores the new space too.

Ernie eyes up one of his sheep from the new vantage point. The many south-facing windows and patio door overlook the main paddock, so he'll be able to supervise the sheep from a position of comfort!

Since I've been beavering away on the new building, Aimee has taken over my regular summer job of keeping the garden weed=free. Proper job! Just look at those nice clean rows.

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