Hanging existing loft floor joists on new RSJ

[wwwebber]

Hi,

As part of my loft room renovations we need an RSJ installing at floor level to support a purlin that has been cut (long story). This RSJ will pretty much sit on the existing floor joists and be supported by brick wall at both ends. This RSJ will be perpendicular to the floor joists so I think maybe I could re-enforce the 3x2 floor joists too by hanging them off the RSJ that will be above them - can this be done and is there a recognised type of hanger that can be used here ?

Thank you.

 

[^woody^]

3x2 floor joists? Boing!

Any hanger can do this. But how to deal with the floor rocking sideways is the thing. Is this being designed professionally or are you just throwing it up?

 

[wwwebber]

The RSJ to support the purlins will be installed by a competent builder. The floor already exists - its just a matter of taking advantage of the RSJ further by providing extra support for the floor joists. For further clarity, the RSJ will sit across where the joists are at mid span where a loft "dwarf wall" was so I am hoping it can provide some extra support in the middle of the joists span as they are already fully supported at both ends. As I've already said they are only 3x2 so will need this support if I can do it. I am also considering laying some 3x3 alongside it but that's another story. I hope this makes things clearer.

 

[Ian H]

Don’t do the 3x3.

Can you get under the 3x2’s for a joist hanger? Otherwise you might be better bolting a timber into the RSJ and coming off that with something bigger ,5x2 or whatever.

 

[wwwebber]

Don’t do the 3x3.

Can you get under the 3x2’s for a joist hanger? Otherwise you might be better bolting a timber into the RSJ and coming off that with something bigger ,5x2 or whatever.

I see what you're asking - No, I cant get under the 3x2s unfortunately - they're busy holding up ceilings that we have no plans to disturb. I cant lose height in the loft or the rooms below either. So as you see I am left with either providing extra support to the existing 3x2s by somehow utilising the RSJ I mention or laying new 3x3s side by side with the 3x2s to do the same job. Or even both. Am I onto a loser here ? or can I do something like what I am suggesting ?

 

[Ian H]

The hanger would normally go under the 3x2 then up onto a timber in the RSJ.

I’m sure there will be something you can do, even screwing an L shaped strap to the top of the 3x2 and then into a timber in the RSJ.

I’m sure someone that knows more than me will be along shortly.

 

[wwwebber]

That is useful thank you. So essence, if I get some timber bolted into the RSJ then that opens up a variety of methods I can use to strap joists to it that are already in situ.

Cheers.

 

[Ian H]

Yes, that’s right. You could get your rsj pre drilled for bolting the timber in.

I used this type:

https://www.screwfix.com/p/sabrefix...B1s97H3kTZOIv-zhr58aAorlEALw_wcB&gclsrc=aw.ds

If you could spare an inch of head height you could hang 4x2’s between your 3x2’s and keep them a couple of mm off the ceiling. Can’t be much of a span with it having 3x2’s now.

 

[^woody^]

The RSJ to support the purlins will be installed by a competent builder

But who is doing the designing and specifying of the method for supporting the joists?