Thanks, that's really helpful! I'm thinking of something along the same lines (limited headroom, dropping ceiling + dormer was too expensive). Had been wondering if beams between party walls was legit, time to get the measure out!
I bought two 250x75 (I think) bolted them together and fixed to heavy duty joist hangers. I also had them put into the attic when I had the roof off to be re-roofed.
If I was doing it again I would probably use steel beams onto padstones built into the wall - however its not fallen down yet...
Thanks, that's really helpful! I'm thinking of something along the same lines (limited headroom, dropping ceiling + dormer was too expensive). Had been wondering if beams between party walls was legit, time to get the measure out!