Joist hangers hanging off bottom of RSJ

[kingandy2nd]

Hi all,

Getting near to doing my flat roofs now, and was working out the heights of the joists vs the wallplate and the RSJ on the other side.

I’m using the following joist hangers:

Simpson Strong-Tie JHA270/75 75mm Jiffy Joist Hanger

With the current heights involved, the joist hanger would need to hang off the bottom of the rsj by approx 60mm.

Would this cause any issue?

To get my heights I’ve used an offcut of the 8 x 3 that goes into the RSJ.

I could increase the thickness of the wall plate to gain some more height, but the hangers then start going off the top end of the 8 x 3.

Ive seen some pictures where timber is fixed below the rsj as well as in the web, is that worth doing in this case?

thanks
Andy

 

[KenGMac]

kingandy2nd, good evening.

Suggest you have a look at the link below, especially the last page?? it describes your problem and what to do with it.

Ken

https://www.metrofixings.co.uk/pdf/JHA_Data_Sheet5.pdf

 

[kingandy2nd]

Hello @KenGMac

thanks for your comment. I had seen the guide (I actually bought my fixings from metro).

the diagramed refer to a different hanger that has a top fixing as well, I think mostly for loft floors.

my hangers are face fix only, as I can’t do a top fixing. I think there is suppose to be some of the hanger below as otherwise you could only using them for fixing into 9+ Inch timbers.

thanks
Andy

 

[Ian H]

Mine are like that but also folded over the timber at the top before they went into the RSJ.

 

[^woody^]

There's nothing wrong with doing it like that.

Strictly, there should be noggins in between the joists to prevent twisting, so you are doing that you could nail those to the support timber too.

 

[kingandy2nd]

Thanks guys - yeah the plan is for noggins. Will fix them as you suggest Woody. Ta