Round wood timber frame pole barn

Hello everybody,
I have been wanting to build a new blacksmith shop for some time now, and this winter an ice storm brought down an oak on my old shop.Luckily no one was hurt, also my bellows, anvil and Jotul 118 clone were unharmed.

Let me say this will be a shop that doesn't have to follow code or last 30 years(even though I think it will). So my plan is to build a round wood timber frame pole barn, that is 12ft by 16ft.I plan to use oak for four of the in ground posts, two more will be (gasp) cherry, which is actually quite rot resistant. I have a dead wild cherry that we cut 10 years ago plus it was already dead a long time and the heartwood is still solid.Cherry will also be used for wall plates and rafters.The walls will be clad in slab wood from a local sawmill. I was originally planning on using slabs for the roof also, but then I was thinking about it and slabs are all sap wood, which rots faster.What do you guys think? If not I'll use catalpa shakes for the roof. In Ben Laws book Roundwood Timber Framing, he says oak is unsuitable for round wood timber frame, because there isn't enough heartwood. From what I understand oak sapwood is almost as strong as oak heartwood, although less rot resistant. The sap wood in the ground will rot in a couple years most likely but there will still be 6-8 inches of heartwood left. Since the oak is only for the posts, with the exception of one wall plate, I don't know if it is an issue because the posts have the tenon which would be in the the heart wood.My next question is the oak posts are still green and the cherry has been down for 3 years and probably drier then the oak. The oak will dry and shrink in the mortice but how much and is it an issue I should worry about? For pegs I intend to use catalpa which is a fairly soft hardwood. Ben Law uses oak so it seems he thinks it is a stress point. I think a timber frame could be built without pegs and unless a giant or dragon came along you'd probably be fine. I still think they should be used but is oak or other hard woods really needed?I am going to burn the ends of the posts and soak them in used motor oil or possibly linseed oil.

Thank you for any help
-The son of Ivan

Hi Ivanson...

Welcome to Permies!!

Let see if I can help some...

I was originally planning on using slabs for the roof also, but then I was thinking about it and slabs are all sap wood, which rots faster.What do you guys think?

Pine tar oil could address this as well as a good treatment of a product like exterior grade "land ark," though for roofs...pine tar oil is the best traditional treatment.

If not I'll use catalpa shakes for the roof.

Even without pto on a 16/12 pitch (53.13010235 degrees) you would get 50 years (maybe even 100 plus depending on other variables.)

In Ben Laws book Roundwood Timber Framing, he says oak is unsuitable for round wood timber frame, because there isn't enough heartwood.

Creator love him Ben is a great fellow...but reinvents way too many wheels...

I must say I read him as a very experienced novice and thinking of deep thoughts...not a traditional Timberwright or woodsman in many ways. Take him in small doses and often with a grain of salt as well.

From what I understand oak sapwood is almost as strong as oak heartwood, although less rot resistant.

And you would be correct in most cases as sap would in trad frames have little to do with the durability of the frame.

The sap wood in the ground will rot in a couple years most likely but there will still be 6-8 inches of heartwood left.

That is simple...don't stick it in the ground. Ben's "round wood" is romantic at best but not always the fastest modality. Try just a simple "Cruck" timber frame of the like and you would be better off (as well as have something that you could sell if needed and our move should you choose.)

Since the oak is only for the posts, with the exception of one wall plate, I don't know if it is an issue because the posts have the tenon which would be in the the heart wood.

Nope...not an issue.

My next question is the oak posts are still green and the cherry has been down for 3 years and probably drier then the oak. The oak will dry and shrink in the mortice but how much and is it an issue I should worry about?

Nope...not an issue.

For pegs I intend to use catalpa which is a fairly soft hardwood.

Not recommended even a little bit for your plan...stick with oak, cherry, or hard wood.

I think a timber frame could be built without pegs and unless a giant or dragon came along you'd probably be fine. I still think they should be used but is oak or other hard woods really needed?I am going to burn the ends of the posts and soak them in used motor oil or possibly linseed oil.

Trunnels (pegs) or wedges are a "must have" in almost all designs, unless you get into very advanced Asian timber framing systems that us "tessel tenons" and other "thread" tenon designs. Not worth the effort. I design/build many in Asian modality, as that is my specialty. I prefer no oblique braces (only horizontal methods of bracing) with either "trapping" gravity joints and/or drawing wedge systems.

That should get you thinking some more thoughts...good luck.

Regards,

j

Thanks for the response!
I though about using pine tar also but it seems really pricey not to mention dirty to produce so I think that's out for now.Ok shakes are labor intensive but they're still free which is nice.I kind of agree about Ben Law reinventing the wheel, he talks about round wood timber as if it's a radical new invention in green design when it's really been going on for centuries.I still think round wood timber has a purpose, it can be done for free, uses little to no gas, use smaller trees and uses the natural strength of a tree. The reason I will be setting the posts in the ground is it would double the work to build a foundation and a floor frame and I'm moving in a couple years so I won't benefit from the added labor. Its more of a free experiment in timber framing rather then how you would want to build a house.I think it should last 20 years easy and then if they want they could jack up the posts and build a foundation. For pegs, I have the options of cherry, oak, mullberry, and hackberry which is best?
Thanks again
-Ivanson

For pegs, I have the options of cherry, oak, mullberry, and hackberry which is best?

For your application and goal, any would be fine...I would recommend oak, then cherry as a second choice.

Regards,

j