Timberframing! Big Honkin' M&T with a router!

[Lynn Kasdorf]

Well, on my barn fixup project I'm getting into some real timberframing. Last weekend, I cut scarf joints on 2 6x8x15' white oak timbers. I made a template out of 1/2" birch ply screwed this to the side of one timber at the end where the splice goes. I hogged out the bulk of the wood with my prazi chain-saw beam cutter on a skil worm drive saw.

Then I used a top bearing pattern bit in a router to cut exactly to the template. Repeat this on the other side of the timber. Then, lots of chisel work cleaning out between the 2 sides. Then, repeat for the other timber.

Fitting these things is a real bear. Since each timber weighs something like 400lb, you don't just pick them up and shove them together. I picked up one piece carefully with my skid steer and forks and gently maneuvered it into position. Then, I pull the joint together with come-along and chains.

Of course, the joint needs refining- I kerf the joint with a hand saw. Pry the thing apart with a big pry bar, remove wood here and there with a chisel. Pick up with the skid steer and try again. Repeat about 3x. You get the idea. Pull the whole timng together, run a string from end to end to verify they are lined up, then drill and peg the joint.

This weekend I'm cutting 8x8 white oak posts with big tenons on the top that go into mortises on the beam.

I'm planning to cut the 8"x2" through-mortises with a router, a guide bushing and a template. I have a 1/2" diameter straight bit with a 3" long cutter. I bought this at a woodworking show from one of those no-name $5/bit vendors, and I've never seen another that long. Perhaps it is too dangerous because you could easily over stress such a long cutter and break it off- I don't know, but it has proved very handy.

I figure I'll cut as deep as I can go from one side, then mount the template on the back side and go as deep as I can. Then drill and chisel out the remaining in-between wood. Obviously, I'll have to take these cuts in many passes of ever increasing depth.

The posts get pegged into the beams, then the spliced 22' long beam with 3 posts will get lifted into place with my backhoe and forks and some sturdy helpers.

Working with these huge timbers is challenging, but really fun, and a great excuse to buy more tools (beam cutter, huge chisels, etc).

I'll post pics tonight.

[Doug Shepard]

You've got a lot of work ahead of you. I happened to catch a show on either A&E or History Channel last weekend (cant remember which and only caught about 15 mins of it). They had a tour through some outfit that was pre-fabbing timber framing structures. They were feeding big 8x8's around like toothpicks and running them through all sorts of specialized milling machines to cut all the M&T's, dovetails, bridle joints, etc. They made it look positively easy. Even using power tools you're going to have plenty of sweat-equity invested. Looking forward to seeing your pics.

[Michael Ballent]

Sounds like you are going to be busy... If you need some more long router bits you can get them from magnate. I use their bits for my Legacy Mill and they have held up pretty good. Their WWW site is http://www.magnate.net

[Scott Lemmers]

Post some pictures of the barn!!
I am going to start a similar project on the new property I just purchased. I may be looking to your for some advice.

[Lynn Kasdorf]

Here is a shot of the tall side of the bank barn up on cribbing blocks while the posts are being redone. The beam I am making goes in the smaller section with the window on the left in the photo. This is a somewhat newer addition to the original 1849 barn. You can see my old new holland skid steer with homemade forks that I use for manipulating the timbers. And junk- lots of chaos- until the barn is habitable, the place is a real mess. Many of my large machines are outside under tarps.

Below that is a shot of the scarf joint opened up and the 1 1/2" framing chisel I am using. Then a shot of it fitted together and drawn tight with a comealong. The timber on the right is about 1/4" wider.

When I do the big M&T joints I'll post pics of those. This is my fist serious timberframing experience. I have fooled around with timberframe joinery with 4x4 pressure treated landscape timbers, but this is the first time doing the real thing. This scarf came out a little loose- I plan to drive in shims when it is in place.

[Jerry Clark]

That is really neat Lynn. I saw on This Old House many years ago when they rebuilt a timber frame barn and did all the cutting and fitting by hand. Lots of HARD work. Good luck on your project.

[Kelly C. Hanna]

I love watching shows dealing with this type construction (and log home building too). I think it's an art taming those huge beams!

[Jerry Olexa]

Very nice work on those joints! Looks good. Be careful!!

[lou sansone]

hi lynn


sort of like building one big piece of furniture. Looks good.

lou

[Todd Burch]

Lynn, how will those two timbers get permanently attached to each other? Wedged trunnels? (I'm showing off with my extensive vocabulary ;))

Todd

[Jeff Sudmeier]

Wow, looks like a great project! Your joints look better than some of my "fine" joints :)

[Scott Lemmers]

Lynn,

Wow, you have your hands full for sure!!
Great looking work on the joints.
I have to admit, my project will seem like a cake walk compared to yours.

[Lynn Kasdorf]

Lynn, how will those two timbers get permanently attached to each other? Wedged trunnels? (I'm showing off with my extensive vocabulary ;))

Todd

The scarf joint will be centered over a post and have a through mortise cut to accept the post' tenon. It will also be pegged at an angle into the existing header beam that it is reinforcing.

The existing header beam is cracking at a mortise, hence the need to beef it up. The header beam on the wider section of the barn is in good shape.

Once the new beam and posts are in place, I'll tighten it up with oak wedges, although this will be overkill. The 8"x2" tenon will be in shear and will keep the joint together.

If I end up assembling the beam and 3 posts on the ground and setting in place, I can tighten the joing by driving in wedges from the top along the edges of the tenons- just to make it rock solid. I don't know if it will make sense to try to manipulate this assembly that way or not. I'll get that advice from the timberframe expert that has replaced another huge beam in the barn (8x12).