Construction with green logs as beams...shrinkage issue.

[ayerwood]

Hello all,

If there is already an FF thread on this subject, sorry, and please point me in the right direction.  I am currently building a shop and would like to dress it up a bit with some Douglas fir logs.  The logs will be green.  I also am planning to build some smaller outbuildings this winter.  I am not building a "log building", but rather using logs for some posts/beams and siding it up with cedar.  I love the look!  As my log construction technical skills are minimal(at best  ;D), I wondered how to prepare for log shrinkage on these structures in the construction process? Is it even a big issue?  Special hardware needed?  Design? Pics?  I am stumped on this issue and worry that if its not right, down the road I will have serious problems.  Any thoughts would be greatly appreciated.  Thanks in advance.

[beenthere]

Plan on the D.fir shrinking across the grain, i.e. when used as beams they will decrease about 10%.
The posts will not shrink in length.

[Brad_bb]

You are using logs for posts and beams?  Are you using timberframe joinery?  If so, you will be scribing then?  If so, you'll assemble the frame and it will shrink as it dries but the joinerty helps hold it in location as it dries.

[Rait]

As beenthere pointed out, you would need to worry if the structure is hold up by both horizontal (shrinks a lot) and vertical (shrinks almost nothing at all) members, in your case if the structure is hold up by posts only, you should be fine.
If its the other way around, in here they use adjustable bolted toes, have wooden rings on top of post (to be removed when rest of building shrinks) or adjustable spline.

[jander3]

Green logs stacked as walls (horizontal) shrink 3/4" per inch per foot of wall height (i.e a 6' wall will settle 4.5").  To account for shrinkage  you have to install keys in the windows and doors.    You also need screw jacks for columns.   

Here is a blog post that shows you how to install a window....


http://peelinglogs.blogspot.com/2010/11/log-cabin-window-installation.html

Be careful, cutting a keyway with a chainsaw is the most hazardous log activity in log building.

If you are using green logs for post and beam construction, shrinkage won't affect you much.