loft conversion new joist support

1 Oct 2014
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United Kingdom
Hi sorry if this has been answered to conclusion before, but;
I own a mid terrace 1900 house. Floor size of 9m x 4.5m with a supporting wall half way along the 9m span.

Calculating with the live loads and the 4.5m unsupported span, leaves me with a joist of 225x 75mm.

However, the angle of the roof would mean the joists would have to be cut with such an angle that very little meat is in contact with the outer wall. This leaves me with 2 options;
1- bolt through the existing joist and rafter to create a joint to transfer of loads to the outer wall.
2- fit 2 steels I beams along the 4.5m length to hang the new joists. But these would have to be fitted inside a course of bricks, and party wall regs come into play.

My preference is option 1. But what will building regs say about such a method?

I have asked a structural engineer to look at this but he gave no assurance that building regs would signoff on such an old house (hence he didn't get the job!)


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He said either would work. But bolting through would be the most cost effective solution.

My gut says the loads will be fine with option 1. But option 2 is the more simple structural calc to prove.

Its a cost vs calc balancing act I guess.

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