Good catch, Scott--

On Fri, Jun 29, 2012 at 11:52 AM, Scott Stager <stagers@m...> wrote:> So
you are milling and building in quick sequence? =C2=A0No drying?
=C2=A0Tell us how that works. =C2=A0Even if the construction "holds" it
in place as it dries,
> doesn't shrinkage create problems?

I'm not an authority on wood moisture and shrinkage, but let me start by
reviewing the basics--

Wood moisture level. I have a moisture meter, and the numbers I've
found so far--

Green trees on the stump, about 40% Spruce logs on the rack, peeled and
air dried for two weeks, about 20% Milled lumber, cut today, about 12
to 14% Fiber saturation point (from literature), about 20%. This is the
level where the wood starts to shrink and check. It's also the maximum
recommended for use as firewood. Equilibrium moisture in our area,
about 4% (this is unusually low--it's usually more in the range of
about 5 to 6%)

Shrinkage--lengthwise shrinkage is usually very small. I don't have a
number, but we assume it's near zero. Radial shrinkage--for log walls,
about 1-1/2" to 2" total over four years, or 1.5" for a door. Windows
need at least 1" shrinkage allowance.

Techniques to accomodate shrinkage--

For log walls,
1.  Assume that the logs will check (e.g. crack). Usually, the biggest
    check is the shortest distance to the heart of the log, so scribed
    logs tend to check inside the walls where you can't see them. Neat,
    huh? The principal accomodation for shrinkage checking is to avoid
    twisted logs, especially left-hand twists.
2.  Allow plenty of room on top of doors and windows for settlement.
    This takes some getting used to and some joinery, but it's not
    that hard.
3.  Build the walls and occupy the house for a winter before you do the
    final sealing and chinking. We chink the inside with an acrylic
    latex product made for the purpose, foam all the windows and door
    openings the first year, then reseal and do the outside chinking the
    next summer. The first winter is a tough one, but you learn the
    lessons fast.

For stick build houses--
4.  Framing will twist and bend if you let it. Don't let it--just get
    everything nailed up while it's straight. Framing is very
    accomodating for green woodworking, because it's used for supporting
    loads along the length of the wood, so the shrinkage doesn't matter.
    As an aside, this house will be framed with 1.5" x 8' studs. They
    make for a very strong wall. The floor joists and rafters are 1.5" x
    12". Why? Insulation levels.
5.  Radial shrinkage in floor boards and wall panelling is unavoidable.
    Work around it. This probably means buying something nice for the
    floor (T&G or plywood), and using lap siding or board and batten for
    the inside panelling. Yes, you will have a fire hazard inside the
    house due to exposed wood. The alternative is sheet rock, so--- Tim
    used 1-1/8" tongue and groove plywood for the subfloor, and plans to
    add laminate finish flooring later. I used kiln dried 1.5" spruce
    T&G. Ben did multiple layers of locally milled spruce lumber.
6.  Spruce seems to be really good about not splitting as it dries, even
    if you nail it wrong, by which I mean even if you put two nails side
    by side in the same board. A better technique is board and batten,
    with one nail in the middle of the board, and one nail in the
    batten. Lap siding is nailed with one nail in each board, located
    just above the underlying board.
7.  Lumber air dries much faster than you might expect, especially when
    it's milled thin. We use 3/4" lumber for lap siding and for interior
    panelling. A couple of weeks will help a lot, but there is a trade
    off with color change. Log oil helps, because it has some coloring
    to prevent sun damage.

PK
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