Timber for garage roof rafters

[spada01]

I'm building a garage and am going to use 6 by 2s to span the width to take a flat felt roof.

What sort of timber do I need? Will C16 do as it's going to be dry, or does it have to be treated and is there a certain strength and type (planed, saw cut etc) that I should specify?

 

[mikric]

How wide is the span

 

[spada01]

4 metres

Also, what timber is best to use for the wall plate? I was thinking about 4 by 2 laid sideways (garage going up in celcon blocks 100 wide)

 

[^woody^]

150mm joists wont span 4m. You need 170mm @ 400 centres otherwise 200mm joists

You don't have wallplates for flat roofs

You can use plain or treated, but treated are obviously better for a roof which might get damp and suffer insect attack

 

[spada01]

150mm joists wont span 4m. You need 170mm @ 400 centres otherwise 200mm joists

You don't have wallplates for flat roofs

You can use plain or treated, but treated are obviously better for a roof which might get damp and suffer insect attack

Thanks Woody. I watched my neighbours extension going up and he has a piece of timber lying across the top of the wall and the rafters come off this. Isn't this a wall plate and surely one's needed for a flat roof to help distribute the load on the blockwork?

I've been using this guide which shows a wallplate too:
http://www.delston.co.uk/joists.htm

 

[^woody^]

There is no load to speak of from a flat roof.

A wall plate is unnecessary, as the joists can be just laid on the masonry and then the walls built up to restrain the joists, stop them twisting and seal the garage.

If you fit a wallplate then you should also fit noggins at the bearings

 

[spada01]

There is no load to speak of from a flat roof.

A wall plate is unnecessary, as the joists can be just laid on the masonry and then the walls built up to restrain the joists, stop them twisting and seal the garage.

If you fit a wallplate then you should also fit noggins at the bearings

All now makes sense. THanks