How do I build a joist into a wall?

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Sorry, another joist related question from me...............

When I build a joist into a new wall, how do I actually do it?

My plan is for the joists to sit directly on top of a course of blocks, and then the other end will be on a joist hanger attached to a ledger board.
I will take the level from the top of the blocks.

I had assumed that I would cut a block so that the vertical edge was in the right place for the side of the joist.
Position the joist next to the block, and then place the next block.

Joists will be on 450mm Centres, so each block will need to be cut down accordingly.

Do I bed the joist in Mortar on all 4 sides? ……………….. and then seal with Silicone afterwards.

If I opt for a joist shallower than 220, do I notch the blocks so that they encapsulate the joist, or do I cut them off vertically, and just fill the void with Mortar?

Originally, I was going to fit 220 Joists so that I could get loads of insulation between them, but on thinking about it I think I would probably be better off fitting shallower joists and then fixing Celotex directly to the underside.
 
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If you use the full 220 mmm for fibre-wool, you will save yourself a lot of money and have better long-term insulation.
 
You put all the joists on first, sat directly on the blockwork, they should be spaced at the required centers. Then be secured by nailing a batten accross the top, far enough back so you can get the (cut) blocks in.
For 50mm joists at 400c the blocks will be about 330 long. These should be fully mortared in. If the joists are below the top off a course (of block)
just fill the void with mortar :)
 
As the young gentleman above has said.
Make sure joists are regularised.

Regards insulation if floor is 18mm chipboard, joists are 50x200 at 400mm centres and 12.5 firelune plasterboard, then you will need 165mm of XR4000 Celotex to give you 0.16W/m2K. This will comply with current regs and will fit inside joist void.
oldun :cool:
 
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As the young gentleman above has said.
Make sure joists are regularised.

Regards insulation if floor is 18mm chipboard, joists are 50x200 at 400mm centres and 12.5 firelune plasterboard, then you will need 165mm of XR4000 Celotex to give you 0.16W/m2K. This will comply with current regs and will fit inside joist void.
oldun :cool:

i would like to know.... i can remember quite recently where you were not allowed to build joists into a wall. there was a shoe thing to meet the regs at the time.
 
I think you're referring to the "joist seals" used to achieve compliance with Part E and Part H in terms of air leakage and heat loss?
 
i would like to know.... i can remember quite recently where you were not allowed to build joists into a wall. there was a shoe thing to meet the regs at the time.

Joist hangers are metal shoes that can be built into the wall, and then the joist sits in the metal cup that hangs out from the wall.

Joist Seals are rubber seals that you can use to seal the gap if you opt for building the joist into the wall.

Joist seals seem like a great idea, but thay are a darn sight more expensive than sealing the gaps around joists with Silicone. I should also imagine that they make it much harder to level the joist.

My BCO said that although regs do advise that all joists are mounted in joist hangers, he would still prefer to see them built into the wall and so has advised me to go down that route.

Thanks for your tips everyone.
 
People tend to go for the easier option and hang the joists but after completion, the floor slightly bounces, then they wish they had built them in.

And... hangers are normally recommended between attached buildings (i.e. semi-detached, terrace houses).
 
I think you're referring to the "joist seals" used to achieve compliance with Part E and Part H in terms of air leakage and heat loss?

exactly.... and i thought it was regs...

you live and learn..

or are they still compliant..
 

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