Sawing Posts and Beams for a Timber Frame House
Advice for a beginner about sawing and using large timbers. January 17, 2011
Question
I am looking for solid advice on cutting timbers for a timber frame house. I have some perfectly straight burr oak trees with no branches in log lengths of 21 feet. Most diameters were between 18 to 26 inches at breast height before I took the trees down. They were plucked with a crane, so they never impacted the ground. I am new to cutting timbers and saw some posts referring to "free of heart center cuts" and "boxed heartwood cuts." Does it really matter that much? I don't mind if the timber splits a little. The white oak is to be used as the posts in my timber frame for all the bents. The plan is a 42x42 saltbox colonial here in Southern Massachusetts. What advice can you give me?
Forum Responses
(Sawing and Drying Forum)
From contributor S:
Solid advice from a softwood sawyer: Diameter of the log is measured at the small end. You will achieve more output if the log you cut is the length (plus 6") you need. There is obviously a physical limit to the size post you can make. The longer they are, the more the bow will be pronounced. Boxing the center tends to minimize the bow. Beams are challenging parts to learn on. I wouldn't recommend starting there.
From the original questioner:
Thanks. I've been sawing off and on for about 4 years now. Timbers wouldn't be where I'm learning. I am thinking about doing a timber frame home, and I'm at the research stage.
From contributor H:
Oak timbers wouldn't be my first choice (softwood). You have a lot more chance for splitting, cracking, bending, and twisting, not to mention they're just a whole lot heavier.
From the original questioner:
That may be true, but if I use softwood, the beam dimensions have to get bigger, making it just as hard to work with them. Softwoods don't have the same strength characteristics of hardwoods. I also have a John Deere 410 to help with the heavy lifting.
From contributor H:
A 12x12 pine beam is still lighter than a 6x6 oak beam.
From contributor A:
You should box the hearts and over-saw the timbers. Sticker out and when they are all done and you are ready to start cutting and fitting, take them out and size them. If it bends much, you can straighten it out some and resquare any twist. If the wood grays or gets dirty, it will not matter. Once resawn and fitted, take good care of it. I do 3 or 4 frames a year in oak and pine.
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From contributor P:
You should apply Anchorseal to the ends of the logs if you haven't already.
From the original questioner:
Is it okay to mix red oak and white oak in the frame for the first floor, then use pine for the second floor and roof? To be more specific, I plan to use the white oak for posts and connecting girts as well as bent girts. I plan to use the red oaks for the floor joists on the second floor, which will be seen from the first floor. Will it look bad, mixing those two like that? I was planning to use pine for the attic floor joists, principal rafters and purlins which will all be seen from the bedrooms; will that look bad? I'm trying to use the trees I have on the property as much as possible without paying someone to truck more trees in. I have some yellow birch and it was suggested I use that for bracing.
From contributor T:
I guess y'all don't have loblolly or longleaf pine up there, but you do have Eastern white pine. All three are desirable species for use in timber framing. Hemlock and fir are even better perhaps. It's true that for long spans the beams need to be sized quite large, but every species has drawbacks.
As to your question about mixing species, yes, it is done routinely by DIYers, but it isn't usually the first choice of designers or engineers. We're remodeling another part of our home and have a 24' loblolly beam clear spanning the entryway to the add-on great room. The beam sits atop two osage posts which are inset 4'. The wind braces were honey locust, but the wife has said they don't look good (don't "color-coordinate") so I removed them and am hunting the log yard for replacements. Probably go with osage.
The loblolly has a 3-sided (natural bottom) 20' long eastern red cedar beam intersecting it. It too is clear spanned, but the ERC is a faux beam supported in the attic by two 3" x 24" glue-lams glued and bolted together; the glue-lam sits atop the loblolly beam which sits atop the osage posts. So the loblolly has a portion of all the weight of the entire structure above the perimeter walls, concentrated in its center.
The osage posts are 10" by 10" so by the time you remove the 8' total inset and the 20" of post tops, the clear span portion of the loblolly beam is only ~ 12' 7" not counting the wind braces (when they are in). The visual effect says to the observer, though, that the pine beam is overtaxed.
We also incorporate post and beam construction in our home and unless they are a builder, guests don't really know the difference. We have hundreds of homes and cabins built from the stable but brittle ERC species here, and the beams are load-bearing. You just have to know the limits of the species. Many will say cannot use ERC for post and beam, but that is not the case - you just have to use more posts, and know where to use them.
From contributor A:
You can mix the oaks without any real problems. But try to use, for example, all white oak for the posts and red for the beams. That way it will look more coordinated. I have mixed all kinds of woods in frames. I try to use all the same in a room. You can frame the pine on the next level above the oak. Use what you have so long as you like it - who cares.
From contributor T:
I like contributor A's point, though - as long as you like the look of mixed species, who cares. Well, if your wife does, that's who.
From contributor D:
I've done quite a few timber frame modifications, assemblies, etc. in SE Mass, and the one thing customers want is the look of old hand hewn beams. My top piece of advice would be to hand plane all the visible sides of a post or beam. Get rid of the saw marks and you'll notice the difference. It doesn't take much time and the hand plane with a curved blade will look almost like hand hewn. You can even add the axe cuts if you want. Mixing the materials is no problem and would have been done with an original building. Contributor A had good advice about locating the mixes.
From contributor R:
Ensure your timbers are very square. Deviations from square will make open joints in your frame. Stick to conventional joinery techniques and typical timber frame open spans (12' is typical). A 42' x 42' is an enormous frame for a home.
