The starting point for this project is a reinforced concrete raft foundation which is pretty level but not perfectly square. It is open on three sides with an existing wall bounding one of the short sides – the north side. It is nominally 8m wide and 4.5m deep. This is the slab immediately prior to the pouring of the concrete (21-Mar-19). Note the wall at the far end of this picture. That far wall of the barn it to sit on top of this wall.
Marking out was an iterative process. Given that the wall was immovable, we used that as our reference. The task initially was to identify the largest perfect square that we could put on the not perfectly square slab. We started by striking a line perfectly square to the wall from the rear end of the wall (right in the above picture) as close to the edge of the slab as possible. We did the same from the other end of the wall and then across the end.
This gave us a square 8134mm wide and 4565mm deep. I then calculated where the post centres would go and what the diagonal distances would be between the post centres.
With these calculations to hand I set about marking precisely where centres of the six full length posts should sit. I marked these by inserting a rawplug and screw.
I was now ready for the brick plinths to be put in place. Read about that here.