Lateral support straps for joists

[acurachris]

Hi

I am nearly at first floor height for my extension and I have made a hole to check the existing floor level. The bottom of the existing floor joists sit level to the bottom of the hole I made and the top of the joists level to the purple line in the picture.

Regs say:

• Restraint straps must turn down the cavity by at least 100mm and be tight against the face of the wall.

The problem I have is when i install the lateral support straps, they are not going to sit on top of a block.

The regs say rebate the straps to allow the floor covering to be laid, so i could do this but they'll need rebating about 30-40mm down the block, is this normal and acceptable?

Hope this makes sense!

 

[^woody^]

What exactly are you doing? Does it actually need straps?

 

[acurachris]

I'm installing the first floor joists. I'll need to strap them to the parallel walls as per my regs below.

"Provide lateral restraint where joists run parallel to walls, floors are to be strapped to walls with 1000mm x 30mm x 5mm galvanised mild steel straps or other approved in compliance with BS EN 845-1 at max 2.0m centres, straps to be takenacross minimum 3 no. joists. Straps to be built into walls. Provide 38mm wide x 3⁄4 depth solid nogginsbetween joists at strap positions."

 

[noseall]

You need to cut the masonry to suit.

 

[noseall]

The regs say rebate the straps to allow the floor covering to be laid

This means you need to chisel the straps into the timber joist by a few mill so that the strap does not foul the floor deck.

they'll need rebating about 30-40mm down the block, is this normal and acceptable?

Yes. It is how we do it all the time. You'll have even more fun if you have a masonry gable end.​

 

[acurachris]

You'll have even more fun if you have a masonry gable end.

I do have a masonry gable end (two actually - L Shaped extension!) although the joists are not running parallel to this, so this wouldn't need strapping to the joists would it?

 

[noseall]

I do have a masonry gable end (two actually - L Shaped extension!) although the joists are not running parallel to this, so this wouldn't need strapping to the joists would it?

The rafters (not the joists) will need strapping back to the masonry. It's to stop the gable being blown out.

Edited corrected

 

[John D v2.0]

I'm no builder, but lateral support straps are for benefit of the wall not the joists. So on an existing cavity wall that will end up less exposed, it's unlikely to be needed unless there is some additional factor of passing that support on to the external wall.