good morning everyone ,
I'm attempting to build a post & beam / log cabin garage.... 8" x 8" upright posts / 4" x 8" sill & header plates / uprights placed at 8 ft on center. overall size = 24 x 60.( 5 bays )
A few questions are
1. what dimension would be best for the tenon going from the beam into the sill & header beams.
2. what size peg is best
3. what is best way to join sill & header plates at the 4 corners of the building ( while also tenoning 8"x8" post into them.

any suggestions or reference to a good book would be greatly appreciated.
thanks fpr your help.
t. mark anthony - TMA

Hello TMA:

Well quite a project but I am alittle confused, your building is 24 feet wide by 60 feet long, and it is 5 bays with uprights at 8 feet, that doesn't work out, my math says 5 bays at 8 feet apart equals 40 feet in length, but maybe I am missing something.

For starters I suggest tenons on the top and bottom of the posts to be 2" by 7", this allows alittle for shouldering, and I would let the tenons to go right through the upper and lower plates, making them 4" in length.

I would use 1" hardwood pins but others might argue differently, and don't forget to design in wind\sway braces in the appropriate spots.

As for the corners, I believe that the building inspector from your area might have something to say about connections such as this. You no doubt will have to get an OK before you start construction. He may require metal connectors of some kind to ensure the building code is followed.
Good luck NH

Mark:
You should spend some time reading up on timber frames. There are several good books available through the guild on the subject. Each or any one of them will give you a good understanding of the subject and help answer your questions.
NH has given you some good advice on tenons. But each frame is different and without knowing all the details, such as roof construction method(s) a 4x8 plate might not be correct. And if your dimension of 60' long is correct (or even 40' long) then you're going to have to make a scarf joint somewhere in the plates and the sills. The location of the scarf joint can effect it's strength and this should be designed correctly.
There is a series of articles available by download (I believe) from the guild which shows different types of joints, including scarf and corner posts connections.
But as I mentioned the whole frame design needs to be considered to understand which one is correct.
Planning the correct frame, now, instead of after it's too late will save you lots of time and money.
Good luck with your project. Jim