Due to my inexperience I chose to spend a little time working out a Sketchup model of what I wanted. This was an excellent way for me to understand how the frame would go together and what measurements I needed. Every piece of the build could be zoomed into and panned and rotated so it really was an invaluable tool for me.
Right, the frame was made from 100x47mm C16 regularised treated timbers. The reason for the double sole and top plate was so that the frame could be made in 4 large pieces and fixed to the first plate. Each corner was planned to overlap the timber below it so that if the half lap for the front elevation sole plate was at the bottom, then the frame section would be the same to sandwich in the corners. The same technique is used for the top plate so that all the timbers are overlapped and stronger joints.
The frame members we are cut at the same time then each section was laid out on the floor, 90mm nails fired through the top, bottom and toe-nailed each side so each timber end had 3 nail fixings - very solid. If the frame timbers had been cut and fixed in-situ then you'd only be able to toe-nail the fixings. These frames were a two man lift to carry to the bottom of the garden and once lifted into place another pair of hands would have been preferred. Instead they were screwed into place with some cross braces and then fine tuned one corner at a time.
Each corner would end up being 150mm wide so you'll see that instead of 3 timber members attached side by side a spacer is used top and bottom.
You'll see the bottom of the frame bridges the door opening, which is done to give stability to the frame and to stop it twisting until it's fixed in place, then it can be easily cut out after. You'll also notice that the door frame is stepped back 50mm as this is where I wanted to add the 150mm timbers which run vertically in line with the edge of the brick. This is the mistake I made as now these timbers would be 50mm above the first sole plate timbers. I could have fixed it and might still do but it's not having any structural effect. I'll show the photos of it later.
I wanted to double up on the timbers around the door, the sash window and the midpoint where the ridge board would be sitting on but around the stable windows I opted for a single timber. This would prove a small problem later on when fixing the cladding. The frame was nailed to the sole plate every 300mm or so - it's easy to carried away with an air nailer and blast around the frame shooting nails into everything. The frame was tied together with nail plates and then later I'd add another top-plate that would tie the corners together even stronger. I did have a few nails bounce around when adding the next timber as the metal plate below the corners sometimes bounced the nails of course!
This is a close up shot of the twisted front corner. The first sole plate looks nice and level but you can see the frame plates being lifted, only slightly but enough to cause a few problems later.
This is the offending front corner that's slightly twisted. Although the first sole plate look level it does twist up so that the frame does raise a little out of level. I still thought at this point it would be OK.