Timber Framing with Yellow Poplar

      Advice on using Poplar or other woods in a timber frame for a house. December 6, 2009

I hope to build a timber frame house within the next 1-2 years and have availability of yellow poplar around 24 inch dbh or larger and clear spans of 25-30 feet from the butt end. Is yellow poplar structurally sound/strong enough to consider for a timber frame?

Forum Responses
(Sawing and Drying Forum)
From contributor G:
It all depends upon your building codes as to whether you can use it, structurally sound or not. Around here tulip poplar cannot be used for weight bearing walls in a dwelling. You need to contact your building inspector.

From contributor W:
I agree with the previous poster. Check with local inspectors and engineers to see if they have specs for your codes/species. I know around here with our snow loads timbers are spec'd out for doug fir although some timber frames I've seen are heart pine. Any other species are very difficult to get engineered.

From the original questioner:
Thanks for the info and I will check local codes and also the consulting architect with timber frame experience. It may be best to use the yellow poplar for trim etc.

From contributor S:
I do some work with antique lumber and have seen many poplar beams used in old timber frame buildings. What you have to remember though is in the old days they didn't have log trucks and moving a massive beam was a large undertaking and so they usually used whatever trees were close at hand and were big enough to serve the purpose. If I were building a new home I'd use oak or antique heart pine for the timber frame. You can use your poplar for framing, floors, siding and many other purposes.

If you go with poplar for the floor just remember that you'll get a lot of dents in it, maybe use it upstairs where there is less traffic. You'll want to get a copy of: "Grades, design Values and Span Tables for yellow poplar framing lumber", AG-351 from the North Carolina Ag Extension Service, Raleigh, NC, published 1985.

From the original questioner:
Thanks for the info on poplar uses. I purchased a Woodmizer last year and have been drying wood in anticipation of building our house. We have been married 30 years and hope to break ground next year. She is a very patient woman and so deserving of a solid well built home so I really do appreciate all the info from everyone out there and this site to discuss wood related issues.

From contributor B:
Sorry I'm late in posting - I've been busy building my poplar timber frame.

Click here for higher quality, full size image

From contributor P:
Contributor G has an inspector that has strayed in his interpretation of the building code, this is not uncommon. I was told one time that the only self milled construction wood that would be allowed was red oak. He had a notion in his head but it wasn't in the codebook. Poplar is not prohibited for structural framing anywhere. The first page of every structural framing chapter of the codebook has the law spelled out. Home milled wood may be required to be graded.

So to build "prescriptively”, as opposed to using an "engineered" solution, the lumber is graded. This establishes strength grades, which are then looked up in approved tables and from that maximum span lengths can be determined for your load conditions. This works for any species that you can get acceptable design values for - lumber 2-4" thick.

For heavy timber it can get more complicated. Timber framing is not a prescribed method of construction in the codebook, so technically it’s engineered right off the bat. Timbers 5x5 and larger have a different set of design values than 2-4" thick dimensional lumber. These values are in the back of the "supplement" linked to above.

There are few beam span tables, and there is one on the AWC website but typically beams are sized individually. This gets into engineering so often an engineer's seal is required on heavy timber plans, this does not preclude the use of any wood. Some inspectors will allow the engineer to grade the timbers to their satisfaction for the design. None of that means it can't be done. Not every inspector makes you jump through all the hoops, but don't let him make up his own hoops.

Poplar from my experience tends to check more than I like for a timber, I prefer to use it for dimensional lumber. That’s more personal preference than anything. Poplar also tends to fail quick, and it is not a long grained and stringy wood.

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