Putting a run-off angle onto a flat roof

[markf]

I will be installing a new flat roof on an extansion being built. I want to have the roof at a slight angle/pitch to allow water to run-off into the guttering.

Is it possible to but pre-cut timber in a wedge shape that will sit on the joists (joists are 3.5m long) to give me the angle before fixing the roof deck boards, or will I need to cut these myself? Do such things have a particular name?

Thanks

 

[masona]

Do such things have a particular name?

Yes, there're are called "Firring". Normally start at 2" to the length of what you need. Timber merchant can cut them out for you. My local timber yard buy them in treated at pre-cut at 3.6m long, then cut off the length you want.

You fit the firring on top of the ceiling joists, bearing in mind some building regs require air cross flow in which you put down 2"x1" in opposite direction of the joists then firring on top in line with the joists.

 

[markf]

Thanks Masona