Positioning flat roof rafters

23 Jun 2018
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United Kingdom
I'm installing a flat roof on a single storey extension. I'm installing the first rafter and unsure how far it should be from the adjacent wall that runs parallel. Is there a set distance or does butt up to the internal wall ?
I will be adding insulation in between the rafters so not sure if I need to leave space between the rafter and the wall. See illustration please.
As I'm adding firings there will be a 2inch gap which diminishes to zero between the top of the outer wall and OSB, how is this best filled in ?

Additionally, One end of the rafter will hang from the steel and the other end will rest on the wall, is a wall plate required for a flat roof or can the rafter rest on the brick?

Thanks again


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