Saturday, August 11, 2007

I finally got the floor timbers up to the property and onto the pier foundation!

Although these pictures don't tell the whole story, it was a major ordeal getting the very large sill timbers to the site. They are 20' 9"x9" green tamarack and douglas fir. I had to use my Jeep winch and pull myself up, anchoring to trees, to the steepest part of the access trail. It was painful, laborious work. Hopefully I won't have to take my trailer up to the work site many more times! It took about 2 hours and 6 different trees/anchor points to crawl up to the top! My winch is plenty strong enough, but I'm afraid I need a new car battery to keep up.

The sill timbers fit well on the piers. Things were not quite as level as I had hoped, though. I ended up having to shim under the plates with different sizes of pressure-treated boards. I had always intended to put a 1.5" layer of pressure-treated wood between the concrete piers and the plates, but I had to customize the thickness of the pressure-treated layer a bit. I used a 2" chisel and mallet and a hand plane.

Once the sill plates were reasonably level and square, I tightened them to each other with rachet straps and then pegged them. Those timbers are now forever joined.

Since I did not have a power drill out at the site, I used my old-fashioned boring machine to bore the peg holes. It was fun and worked really, really well!

The 1.5" mortises spaced 16" O.C. are for the 2x8 floor joists. These mortises are 4" deep, and the original plan was to cut 4" deep tenons into the joists and just let them into the mortises. This "hybrid" floor framing method which uses traditional sill plates but conventional dimension lumber for joists is described in Chappell's book (page 13, I think?)

Peter, however, recommended against leaving only 4" of support at the ends of the joists. My brother-in-law, Jeremy, pointed out that the joists, supported in this way, might eventually split with the grain, weakening the entire joist.

To play it safe, what I will do is cut the 4" tenon into the 2x8 joists and let it into the mortises and then use conventional joist hangers to support the bottom of the joist as well. After committing to hangers and nails for the joists, the mortise/tenon portion of the floor system seems superfluous. However, I've already cut the mortises.... :-)

Overall, the floor timbers turned out well. There is some minor warping and checking and a minor level mismatch in one corner, but overall the floor frame is solid. The timbers are way oversized, but I like the pure strength in these timbers! Each corner has two 1" oak pegs. If I build the joists and subfloor correctly, this will be a very solid floor.

The tie-down straps will screw into the side of the sill timbers and the posts, firmly connecting the frame to the foundation so that a monster wind doesn't throw the cabin around. The cabin site is generally exposed to heavy winds, so this is an important consideration.


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