Creating Slope on a Flat Roof

[Blokky27]

Hello all

Looking to build a flat roof on a garage about 7m x 3.5m. Joists to run across the shorter span. On top of these I plan to add firrings in order to achieve a slope for water run-off. Would prefer if the slope was front to back or back to front rather than side to side. This being the case I will need to run the firrings across the joists instead of along them which raises two questions.

1. Will the strength of the roof be less with the deck on effectively thinner support, i.e. the firrings (thinking of children going up there despite the fact they will have been told dozens of times not to).

2. How do you run firrings over 7m when they can only be bought in shorter lengths?

Thanks all.

 

[wilco88]

What roofing material are you planning to use?

1. Yes.
Run decent thickness battens across the joists first and add firrings on top of this. Any insulation going in?

2. Personally I'd make my own with a skill saw.

 

[wilco88]

Also, how far apart are the joists?

Make sure you have 1:60 fall