At the moment I have a flat roof on my garage which is 10' wide & next to that is my utility room which is 5 'wide. The flat roof is covered with felt & chippings & covers both garage & utility room as one roof. The joists are 15' long & are supported by the shared wall between garage & utility room as well as being fixed at the ends. The joists are only 4" x2" & are 22" apart.
I want to take out 10' of the adjoining wall to make my garage wider. Is it better to just put bigger/thicker joists in to cover the 15' span, or do I need to put an RSJ in to support the roof where I've removed the supporting wall? (hope this makes sense). if I can put in bigger joists what sort of size would I need to support the roof?
Thanks in advance