Timber framing joints - top tips (preferably with diagrams) thread

[SteveA]

There must be lots of us that make our own, or try to make, or want to make our own buildings/ log drying sheds/ hay barns/ storage shelters/ roundwood structures, etc.

 

I'm no professional carpenter by any standard but always willing to learn more.

eg;

- size of fixings according to the thickness of timber.

- width of a mortice joint according to the thickness of the beam

- preventing roof condensation/ and rot in posts at ground level

- any other stuff!

 

cheers, steve

[ucoulddoit]

Steve

 

Happy to share this although I'm not sure how legible it will be and it is quite a small outbuilding. One thing to note is there is no roof bracing shown. I relied on the steel roof sheeting which was well stiched together at the overlaps and fixed to dwangs along each end of the roof, but others might prefer diagonal BAT straps or something similar.

 

Andrew

[agg221]

Good idea Steve - hopefully this will develop into a really useful thread.

 

A few thoughts based on roof-related things I spent a long time digging around for and mulling over when building my extension roof:

 

In a building without a ridge beam, the rafters force the walls outwards. In a building with a ridge beam, the rafters pivot about the beam and hence pull the walls inwards. This allows you to choose which way round you want to put the braces and any tie straps required by building control which you want to hide.

 

Joints should take out no more than 1/3 of the section of a rafter.

 

The housed bird's mouth is the best joint I can find for fitting rafters to wall plates. The bird's mouth transfers lateral thrust to the wall, but in itself is prone to starting to split from the internal corner of the cut, due to the vertical load. If you house the foot of the rafter into the wall plate, the heel of the rafter carries the vertical load, which means it doesn't split.

 

Construction with a ridge beam is less common, so I ended up having to work out my rafter connections at the top. The step lap rafter seat proved to be a very good joint to fit rafters onto a ridge beam, as it resists any lateral or sliding movement and provides a good pivoting socket.

 

The whole roof would have held together without any fixings - I put some pegs in for security and resisting wind loading but in reality it would probably have been fine without them.

 

I worked out my joints by drawing the two sections, intersecting to the depth I wanted, full scale on a piece of paper (pretty much everything will fit on a sheet of A4). Where I needed to remove material, I split the difference between how much came out of the beam and how much from the rafter (assuming it didn't take more than 1/3 out of the rafter). I then took a thin piece of white plastic (about 2mm thick) and cut it to look like a carpenter's square and laid it on the paper with the internal corner lined up with the line of the beam. Wherever cut lines intersected with the square, I marked the positions off. I could then transfer the square to the beam and mark straight off onto it, with no measuring needed. I made a similar template for the rafter cuts. These saved me hours in measuring and trimming, and everything fitted first time (with a bit of shaving).

 

Alec

Edited October 10, 2015 by agg221

[SteveA]

That's a great start. cheers, steve

[agg221]

A couple of questions if anyone has any thoughts:

 

I need to fit vertical posts between two beams (ground floor and first floor). This will be with mortice and tenon joints, pretty much resisting vertical load only. The beams are 9" x 9" below and 5.5" wide x 8" deep above. The posts will be 5.5" (to match the upper beam) by 4". Any idea on dimensions for the mortice and tenon (single shoulders on the posts or double? Depth? I am anticipating that pegs will not be needed below, as per a sole plate. I could peg the upper ones or just leave them?

 

Because of the construction sequence, the 6" x 9" ridge beam is already in place and meets the upper beam described above in the middle (T-shape intersection). The top of the upper beam is about 14" below the bottom of the ridge beam so a short 5.5" x 6" post will need to be inserted. However, because the beams are already fixed, this can only be slotted in from the end, ie I can't use standard mortice and tenon joints. Any thoughts on appropriate joints which could be used both at the top and the bottom. I wondered about an open mortice and tenon at the top, but what about the bottom?

 

Alec

Edited October 10, 2015 by agg221

[slack ma girdle]

I can bring my shed book with me on Monday, if you are about. It has all the angles and dimensions you will need.

[SteveA]

I can bring my shed book with me on Monday, if you are about. It has all the angles and dimensions you will need.

 

Rubbing my knees at prospect of seeing your shed book Murray

[slack ma girdle]

So long as it is only your knees

[dirtybiker]

Hi, just finished my self build oak frame house. The framing part was done by the Pros at Border Oak but I have a full set of electronic framing drawings if you want them for reference.

Jez

[SteveA]

Hi, just finished my self build oak frame house. The framing part was done by the Pros at Border Oak but I have a full set of electronic framing drawings if you want them for reference.

Jez

 

Hi Jez, I've been following Border Oak on their facebook page.... amazing high quality stuff. I'm very interested to see your drawings as I've never seen any high-end oak frame drawings before.

 

I imagine you must be proper chuffed to have finished a self build in oak! Good man.

cheers, steve