What wood is best?

[oklalogdog]

Happy Holidays everybody! 

I am starting a timber frame barn and have a question about wood.  We have basically two types trees here that are suitable for construction - White Oak and ERC.  White Oak is hard to work with, hard on equipment and is extremely heavy.  ERC on the other had is easy to work with and light.  The Center section of the barn and the widest span will be 20'.

Now for my question.  Is ERC strong enough and suitable for beams, trusses, and etc. or should I go with the white OAK?

[beenthere]

"Strong enough" will depend on the design and the grade of the wood species you use.
White oak is stronger than ERC comparing clear wood to clear wood of each.

Knots and localized steep grain in beams will change the actual strength when comparing the two species.

So no absolute answer.

There are design tables that engineers will use so the end design will depend.  I'd be a bit doubtful on a 20' span of either species at first blush.

[oklalogdog]

Thanks for your reply.  I am a bit doubtful about the ERC but you could park a bulldozer in the middle of a 20'  6 X 8" Oak beam.

[shelbycharger400]

erc is not considered structural by any means.     old bridges usto be made out of white oak for posts.

[beenthere]

Thanks for your reply.  I am a bit doubtful about the ERC but you could park a bulldozer in the middle of a 20'  6 X 8" Oak beam.

Demo that for us. Would like to see it.

[Magicman]

Me thinks that with the bulldozer illustration, you answered your own question.   ;D

[Brad_bb]

Surely you must have more tree species in your area that are suitable to frame with?  You don't have to use all the same type of wood in a frame either.  There are certain woods that are generally not used, like Cottonwood(though I'm sure somewhere there is an old frame with a piece of cottonwood in it).  Soft maple should not be used either.  But there are a ton of speices that can and are readily used in timberframing.  You must also learn to, at a minimum, grade the timbers yourself to know where they can and cannot be used in a frame, or if they should be culled completley.  Knowing how a timber will be loaded, depending on it's function in a frame, is important know where and how stress will be applied and whether a particular defect will be a problem for a given member.  For example, the loading of a post versus a tie beam is very different.  A post is in compression and can afford more defects(and is usually oversized) as oppsed to a tie beam, which will see more stress in tension in the center bottom side of the beam and compression at the top.  Defects at joint should be avoided in general, but especially in joints that will see tension loading.  These are just a few generalized examples.   A good start is to learn and understand the Nelma grading rules for timbers.  The next step is understanding how different defects affect a timbers use, depending on the location and size of the defect.  Learn which defects are not considered significant defects, and learn to look at grain runout.  Some of this is out lined in Sobon books and in Chapell's book.  You should print a copy of the Nelma grading rules(online), and ask specific quesitons here.  Ultimately you want to have an experienced timberframer or practicing engineer experienced with timberframing review the design beforehand to make you aware of what is necessary and where critical areas are.  I feel with anything more than a simple shed, this is money and time well spent.  Where are you planning to get your timbers - a local hobby miller?  a big mill?  a supplier who is familiar with timberframing?
I just did a google search and here is a link to the NELMA grading rules.  You want to look at Section 6 for timberframing.
http://www.nelma.org/reference/standard-grading-rules-for-northeastern-lumber/
Althought this is generally for Northeastern species, they are still good rules to learn as a guide, and you may have some of the same species.

[Al_Smith]

I suppose  it depends on what you have .I can't comment on silver maple but my parents have a  small "carriage " barn made or rather post and beamed with sugar maple  .It's over 100 years old .

The only problem it ever had was a couple of the main posts got a little soft near the bottom which I repaired with steel plates and 8 by 8 oak about 15 years ago .

I have seen in the  past machinery sheds made of eastern cottonwood but they were trussed rather  than post and beam .Extra heavy double plate trussed  bottomed plated and bolted together . If I recall right they used a type of spiral nail to nail the roof stringers prior to the metal roofing because cottonwood doesn't hold standard nails very well .That was back in the 60's .--for all I know they could have fallen down by now-- ???

[oklalogdog]

In reply to Brad_bb

Thanks so much for the info.  and I will download the material you advised me to.

In the eastern part of our state there is a lot of pine of various kinds as well as hickory.  I intend to use what I have on my land however and that is tall, canyon grown ERC and mature white oak. 

I will use white oak for the beams, posts and purlins I suppose and skin it out with board and batten ERC.

Oh and thanks for everyone else's replies.

:P

[Ozarkian]

So Oklalogdog, how's it coming along?  Did you begin the build process yet?  I would be interested in seeing how it turns out.  I am considering similar type build using ERC.  Thanks!  ;D

[oklalogdog]

I have cut some 1" boards for the board and batten and will start on the oak beams very soon.  Right now we are doing dirt work and building rail fences to get the place ready.

When we really get going I will post pictures of the project.  Our intentions are to build a barn first and then our house.

[oklalogdog]

The rail fence is a necessity to keep the cattle away from the building site.  Some things just have to be done first whether we like it or not.

Later