Shaping the Roof – green oak barn

Thursday 4/2/21

Today I started by dismantling the completed truss. I was able to move the king post and principal rafters out of the way but the tie beam was too heavy. I assembled the wall plates for the lefthand bay of the barn on blocks just above the slab and checked that they were square, straight and level. I then lowered the tie beam on to the wall plates, end by end and in stages.

Moving the tie beam down to the wall plate

Once the tie beam was on the wall plates I was able to knock it into the cog joints.

Lining up the tie beam - 2

I then brought the king post back in, put it in a vertical position and rested it on blocks so that its tenon was only 10mm into its mortice in the tie beam.

Erecting the king post

I then located the first principal rafter – this will be to the rear of the building.

Erecting the rear principal rafter

Next I located the front principal rafter and then knocked out the blocks at the bottom of the king post and all elements fell in place – very satisfying! I then pinned the truss together and checked that it was vertical.

Erecting the front principal rafter

I then cut some softwood common rafters, complete with birdsmouth using the template I made yesterday. I was pretty pleased with the way all these elements came together given that this was the result of pure maths (see here and here).

Testing the geometry of the common rafters

Unfortunately, the tent is not high enough to put the full length softwood ridge in place so I cut a shorter sacrificial piece to allow me to proceed to construct the key parts of this end of the roof. I will have to cut the true ridge when we put up the roof for real.

Sacrificial softwood ridge

Tomorrow I want to try and get the softwood hips in place as this will enable me to deduce the exact design of the green oak hips that will sit immediately below them. I need to decide how to join these green oak hips to the wall plate and to the end of the green oak ridge which will sit immediately below the softwood ridge.

Onwards and upwards.




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