Mono pitched roof design

[dajome]

I have a single storey rear extension on my detached house with a mon-pitched roof - standard construction with slates on roof. I want to remove the ceiling joists and rebuild so the ceiling is to the rafters. I presume that to do this I will need to remove the current roof - joist/ rafter construction and redesign a new roof construction of just rafters (to include some velux type openings for additional light). Can anyone advise as to design/ size of timbers, etc. The basic dimensions of the extention is 2.36m across the pitch x 5m long (internal measurements). Also, will I need to submit loading calcs to Building Control or is this pretty basic stuff?

 

[^woody^]

The work will require building regulation approval

You may also need a purlin or beam at mid or 1/3 span to counteract the lack of bracing which the ceiling joists would have otherwise provided to the external wall

So its not just a case of a particular sized rafter section

 

[dajome]

Thanks Woody - any idea where I can find how to spec what I need? Or would it be better to pay a professional to draw up the specs?

 

[^woody^]

If you can find a copy of rafter span tables on line, then they may help. But I think that the requirements for a supporting purlin or beam (or none) may need to be designed or proved by a suitably qualified engineer or suchlike.

You could perhaps do a dimensioned sketch and have a word with the BCO for your area .... he may offer some advice on what would be acceptable, or you may just get a grumpy one and a glazed look