Detached garage. Warm roof, insulated walls

[Russdl]

 

A total of 19 'C' Section steel joists were used for the roof. We had two different sizes, the taller ones were for the larger span at the front of the garage and the smaller ones at the rear. The joist were mounted side to side and the 'fall' of the flat roof was to be front to back of the trapezoidal garage. To get the required fall I needed firring strips on top of each joist but with the fall being front to back and the firing going side to side each firring would be a different size.  

 

I couldn't get a saw mill to cut me 19 firings that were all completely different sizes so I did it with a skill saw. I also put a slight taper on top of each firring so that the roof boards would sit on the whole of the firring. That all seemed to work a treat and was less tedious than it sounds.

 

 

 

The rest of the roof was standard warm roof build up: OSB - Vapour Barrier - 120mm PIR -OSB - EPDM.

 

Getting 56m2 of EPDM up on the roof proved tricky. It arrived rolled up and I thought it might actually roll. Not a bit of it, it was reluctant to go anywhere. In the end we placed a couple of ladders against the roof and then used ratchet straps to hoist it up bit by bit. Once the EPDM was up on the roof the rest was a breeze, really easy to work with and stick down.

 

 

 

For the external wall insulation, we started with a 300mm high band of XPS around the base, sat on top of the foam glass. Above that was Rockwool for the breathability and fire resistance. The XPS was finished in black render and the Rockwool in white render, we then filled the trench around the garage with gravel leaving 150mm of the rendered XPS as a plinth. I couldn't quite get my head around how the finished rendered rock wool would feel, it's quite amazing, solid as a, well, rock. You'd never guess it was rock wool under the render.