Loft conversation Floor joists on RSJ

[Iwhanmer]

Hi
Im converting a loft and need to hang joists of an steal beam totally below the support so that the bottom of the joist hangs 215mm below the bottom of the beam. The reason for this is one of the beams is sitting atop of another and would lose a lot of hight if I can't hang below the support.

I planed on using the Simpson JHA450/50 Joist hanger and they say to hang below the support you require timber bolted into the span of the beam as normal but an additional timber bolted to the top of the beam for the hanger to wrap over (45mm). The problem I have is the beam I am using us UB 356X171X45 and the max hight of the hanger I can find is 475mm so I will not have enough lengh in the legs of the hanger for the wrap over above beam. Is there anyway to support the joist hanger without the requirment for a top timber beam and wrap over. Would maximum nailing into the timber in the web of the beam be stong enough and within regulations? Could I possible just wrap over the timber in the span of the beam and that is enough support?

Any help is much appreciated.

 

[Static]

Can the steels not be designed to span in plane with the support beams? Or have they already been installed?

 

[Iwhanmer]

unfortunatly they have been installed and secured already.

 

[Static]

Have you asked your Architect or SE how they saw this working? Also if the SE needs the floor joists to restrain the support beams?

 

[Iwhanmer]

The Architect believed it would be ok to hang the joists totally below the support so long as they are laterally braced.
I don't believe the support beams need restraining by the joists according to the architect however I will double check with the site inspector.

I have received this email from Simpson:

JHA450/50 can still be connected completely below support without a wrap over from a steel beam with timber packers fixed in the web.

Use the maximum face nailing so minimum 20 Nr square twist nails (10 per strap) without a wrap over and the below support long term safe working load of 4.0kN.

So this looks ok? Unless like you say the beam requires restraint from the floor joists??

 

[Static]

Would seem the way to do it.. but you should get this confirmed by your architect/SE..

I ask about the restraint because with such a large beam it would suggest its spanning some distance.. which is where you get issues with the beam twisting under eccentric loading such as you are doing..

 

[Deluks]

Would seem the way to do it.. but you should get this confirmed by your architect/SE..

I ask about the restraint because with such a large beam it would suggest its spanning some distance.. which is where you get issues with the beam twisting under eccentric loading such as you are doing..

For a loft conversion? Lazy engineer overspecced?

 

[Iwhanmer]

Thanks I have asked the Architect about the restraint again in an email and will let you know what he says could throw a spanner in the works.

If I could go ahead with that plan I could have another problem. Hanging the joist below that beam would mean it could nicely fit into the span of the opposite beam (H= 254mm) and work well for that part of the floor. However there are 3 other beams in the loft and one is only 127 high meaning that the joists would have to sit another 127mm above that beam to bring the floor level. Can you get joist hangers that will allow the joist to sit above the beam. I don't think I could notch the joist as I would need to notch 73mm out of the joist I belive that woudl be more than is allowed?

I can attach the plans if you like.

Thanks for your help!! much appreciated.

 

[Static]

Attach a timber plate to the top of the beam then part fix to this.

 

[Iwhanmer]

Static.

Thank you very much for all your help I think that has sorted it!!!