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Tulip Poplar for timber frame

Started by Horselog, December 14, 2010, 09:28:49 PM

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Horselog

Hello all, I have a customer asking me about using poplar for a timber frame.  I have been around most other commonly available woods for timber frame, such as oak, pine, and doug fir, but never been around poplar.  I know it tends to have a lot of internal stress which can cause cracking, but how much does that actually effect it structurally?  It would be some larger beams, such as 8x16 or 10x16.  Any input would be appreciated.
Benjamin Harris
Appalachian Mountains of Virginia
horse_logger@me.com

Qweaver

I built my entire post and beam cabin using poplar.  The largest beams were 7"x9" seal beams and none of them cracked badly.  But several of the upper posts and beams cracked and a few badly.  Most did not crack at all.  I don't know enough about timber framing to tell you if that would be a problem but it was not a problem for me in post and beam type construction.  I guess that if you had time to let the timbers dry you would be able to select those that did not crack for parts where a crack would be a problem.  I think that cracks in posts makes little difference in strength.  My biggest issue with large cracking was that the cross section of the timber could become way out of square.  I'm sure that some of these experienced timber framers will have some input on this.  See my thread on "building a cabin in the mountains" to see how my poplar timbers worked.
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icolquhoun

tulip poplar is just about as strong as EWP from everything I have read as well as done compression/beam deflection tests on.  It also usually grows very straight and without knots.  Therefore, in my opinion, it's a good material to use, provided you size the timbers/joints accordingly.  I also like the fact that it air dries extremely quickly.  I am amazed at how quickly, in fact.  As long as it is stickered well, it has dried perfectly straight and without warping for me.  It saws/planes/works very nicely provided you have good sharp tools.

I am currently building a 14x16 1.5 story cape with a lean-to off the back using tulip poplar due to it's weight because I plan on erecting this cabin in a very remote area by myself.   

carykong

The 18th century carpenters at Colonial Williamsburg commonly use tulip popular in their reconstruction projects. Their head carpenter attested to me that poplar was a common and preferred timber due to its strength, ease to cut, and plentiful supply in eastern Virginia. I, too, have experienced severe checking with poplar cants. Poplar dries fast so anything to slow the drying process down will reduce checking and cracking. No direct sunlight, cover, treat with sealer.  The 18th century carpenters use a 50/50 solution of turpentine and linseed oil to reduce checking.

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