Toby CambrayWhere the extnesion roof meets the old wall at first floor, I stripped one row of tiles, trimmed the counter battens, screwed 150mm PIR (in 2 x 75mm layers) to the wall to forma plinth similar to the ground floor
The roofers then did some nice lead work to cover and protect it. This was a spur of the moment decision and perhaps not the wisest - it was quite expensive and probably not great on the up front carbon front. I'm feeling the pressure a bit and had to make some quick decisions. It should be pretty robust and looks nice - also a pleasure to watch skilled people doing stuff like lead welding. Didn't get any picture but it's a super cool process to see
It was then on with the framing! Things started to happen very quickly at this point. The details take take all the time, and also the lions share of the cost in materials. All the 2x2 was about £250, a few sheets of 11mm ply for the gussets... First up, 2x2's were fixed to the wall at 600 centres, with masonry fixings.
The structural eng specified a very particular make and type of fixing, which were a bit tricky to get hold of, but are the only ones with a pull out test certification in concrete block. They are great to use tho - no messing around with rawl plugs. I pre-drilled the 2x2s at specified cetres, taking care to cordinate with the mortar joints (as in to miss them). The datasheet for the screws calls for no more than 60mm from block edge. I chiseled off the render in a few spots to locate joints...
And then spaced out the fixings accordingly, as best I could within reason. The windows also got a collar of 2x2 at this stage positioned so as to support the edge of the sarking board. I had to scribe the studs in in a few places such as around cables and bell casts. Here you can see my teporary setting out pegs with the laser sat on one (these are marked off with two or three useful depths).
OPnce the first layer of studs was in, gussets are fixed to the sides. A fair bit of deviation can be taken out at this stage, so the new surface should be much more square and plumb than the original, by adjusting the width of the gussets with the help of the laser. Our walls aren't too bad, ainly no more than 10mm out.
Others (andy simmonds and Tim Hulse, amongst others) using similar details have used factory made trusses, fixed to the walls with shims and brackets. This is probably a bit quicker but the materials are more expensive, so if you're doing it DIY like me the larsen truss arguably makes more sense.
The corners took a bit of figuring out - getting the right order of operations and positioing everything so you can actually get a screw driver in is a bit tricky. I did the short lenght of corner first which was easier to practise on