Position of joist on flat roof information and advice on general building topics, builders merchants, problem builders, DIY Stores etc....

[LAB]

Hi all
At last blockwork on ground floor 6X3 mts extension finished need to fix joists for warm roof, do I fix the first joist on the inner skin blockwork, as someone mentioned in another topic there is a lot of "what to put in to a warm roof but no details of how to install one", any help, please

[welsh brickie]

you lay 100x50mm wall plate level on a bed of mortar on the inside leaf of blockwork.Then start your joists on top.
The joists overhang the outer wall and the fasia is fixed, usually a vented soffit is installed to allow air to ventiate the roof void.
To get a fall for the water to run off you nail a timber fillet to the top of each joist,its 50mm thick tapered to nothing the full length of the joist..You then need to nail wall plate brackets to the wall to hold the roof in place.
Then you can fix your roof boards.A triangular shaped timber is nailed on top of the roof boards around the perimeter to soften the angle of the the felt to the wall and to aid the water to flow to the gutter.
hope that makes sense..

[LAB]

Welsh Brickie,
Thanks again for your help and advice, can you tell me where do I lay the first joist, is it flush with the outer/inner skin then as required 400mm centres, thanks again

[welsh brickie]

yes you can lay it flush with the outer skin of blockwork,remember your fasia board will be fixed on top you need a bit of an over hang to allow for render,so you could nail 50x25mm batten to the joist to pack the fasia out.