Don_P
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# Posted: 4 Apr 2016 01:28pm
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My recollections are similar to Malamutes as far as settling. We had one that settled about 1-1/4" IIRC, that one had just allthread installed after the logs were stacked, no lags or olys or spikes during assembly, which left more gapping and consequently more settling. Shrinkage, initial moisture content vs in service moisture content, plays one part in settling but is not the entire cause. Leaving gaps which later close is another. In scribe fitted work there are a couple more things going on. A fine scribed edge can crush a bit until it forms a wide enough bearing surface to carry the load above it and the copes can spread allowing the logs to settle more deeply onto one another. This is part of why you'll hear a pretty broad range of settlement allowances.
Designing for settlement is something else to think about. It becomes more complicated if you go above one story. If there is much settlement you need to think about plumbing drains, interior support posts, do you want the stairs to slide at the bottom and go out of plumb or slide at the top and change that riser height, interior frame walls need to allow for the exterior walls sliding down, etc.
The old log buildings here were chinkers rather than scribe fitted. They typically did not allow for settlement, window and door bucks ran up tight to the header log with each log course below that pegged to the buck, no settlement allowed in those areas. The corners of course being a stack of horizontal logs did settle, most of those cabins have drooped to the corners over time.
In the post and beam method the vertical post logs or timbers support the header row(s) of logs. Since wood does not shrink appreciably in length there is very little settlement at the top of the wall. If there is log infill between the vertical posts then any shrinkage is accommodated either by allowing the logs to gap between each log or bringing the infill stack down together and incorporating a sliding joint at the top of the panel. With this method floor elevations and roof height do not change.
There are many ways to skin that cat.
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