Loft joists

[messimagician]

I want to put a stronger floor in the loft. At the moment the joists in the loft are only 75x50 with the joints running from front to back of the property. Now I have had a structural engineer around and he said he would have to calculate the new floor as a proper floor because of the spans involved. 3.8m being the largest span

What is being proposed is a steel beam put on to a load bearing wall and into the party wall. Then have the new joists run parallel next to the existing joists.

My question is, how should the joists be fixed at the ends where they rest on wall?
I understand that I will need a timber packer underneath the joists. I'm just not sure on the fixing side as I don't was the joists to start twisting

The house was built in 1959 and built with a hip roof. There is a piece of timber propping up each purlin on supporting walls with what I think you call hangers fixed to the rafters and then to the ceiling joists, these rest on the purlins

 

[Ian H]

Just 1 steel beam?

I bedded a timber wall plate on my central wall and sat the joists into that. I used noggins to stop any twist but didn't fix them to the wall plate, I just bolted the front set of new joists to the rear set.

The hangers will stop the 75x50 ceiling joists from sagging and the purlin supports stop the roof sagging.

 

[messimagician]

Ah ok thank you

Yes usually you would have two steel beams, one wall that's bearing the roof is about 30cm offset from the ground floor wall and is sat across the joists in the living room. The SE said it could cause cracking to the ceiling but he said he would need to run the calculations first

The other half of the house the load bearing wall runs straight up from the ground to the loft which the SE is proposing to use

I'm just waiting to hear back from the SE, it would certainly make it a tad bit easier if I could put two steel beams in as then I could get the joists in through the house rather than taking them through the roof

Also the timber lintels in the bedrooms may need steel plates bolting to them to support the extra weight which is another thing I'm not sure on when it comes to fixing. If it involves having to take the lintel out to fix the plate then I'll just get someone in

 

[freddiemercurystwin]

Stronger floor for what, precisely? Sounds ludicrously over the top to me!

 

[messimagician]

Mainly for storage but I want to put a server stack up there with cctv recorder ect. Seeing as every bedroom as cracking down the centre of the ceiling the existing joists can't take a single person up there let alone any storage.