sub floor

[electrified]

If you puddle the concrete well into the edges and corners there won't be much of a gap.
If you've dug out the topsoil there won't be many weed seeds left.
And don't know about your house but there's not a lot of sunlight in my subfloor (which plants need to grow).
So don't worry about it

That makes sense.

another thing i’m confused about is can i have my internal dpc, one or two bricks lower than my external course?

Can i have full fill rockwool insulation in a 50mm cavity without and damp problems?

And using a wall starter kit, does this require a dpc vertically? (i’m not using a starter kit, i see these wall ties that screw into the original brick and lay on the mortar of new brick)

Many thanks.

 

[oldbutnotdead]

Yes you can.
If you only have 50mm cavity you'd be better off using Celotex or similar- yes it's pricey but is a more effective insulator per mm of thickness (50mm PIR is about the same as 90mm rockwool). If you do use rockwool it needs to stop at the higher of the dpcs (and make sure you don't block air bricks)
If the wall you are building off has a working dpc then no you don't. Otherwise yes put one in.

 

[electrified]

Yes you can.
If you only have 50mm cavity you'd be better off using Celotex or similar- yes it's pricey but is a more effective insulator per mm of thickness (50mm PIR is about the same as 90mm rockwool). If you do use rockwool it needs to stop at the higher of the dpcs (and make sure you don't block air bricks)
If the wall you are building off has a working dpc then no you don't. Otherwise yes put one in.

ah. I’m pretty sure the wall i’m building against does have a dpc ( i’m not too sure though). I could put one in just in case but the mortar doesn’t stick to it very well does it i’ve heard. I can’t see if it does have a dpc as it is rendered. Also i’m going to cut a channel out of the render for both leaves so it reduces water getting into the corner. had other people saying that 50mm cavity is old and the new cavity size should be 100mm. I’d rather a 50mm cavity as it gives me more space. This is what i might do…. 50mm cavity with full fill rockwool or full fill celotex board. But if i have to a 100mm cavity i would do 50mm of celotex tight to the inner skin. Which one would you recommend to me? All i’m concerned about is these insulations bridging the cavity and causing damp. Would it be ok the full fill a celotex board?

Cheers.

 

[dapperman]

Yes you can.
If you only have 50mm cavity you'd be better off using Celotex or similar- yes it's pricey but is a more effective insulator per mm of thickness (50mm PIR is about the same as 90mm rockwool). If you do use rockwool it needs to stop at the higher of the dpcs (and make sure you don't block air bricks)
If the wall you are building off has a working dpc then no you don't. Otherwise yes put one in.

Hi is a 50mm cavity ok to have and can you fullfill celotex board?

Or would it just be better to have a 100mm cavity?

Thanks

 

[oldbutnotdead]

Mortar doesn't stick to much. If you want to put a vertical dpc in crack on, just butter the bricks/blocks where they hit the dpc, it'll be fine.

If building control are involved you'll have no choice about 100mm cavity (or 150 in a few months). You'll get better thermal performance from 100 with bats than from 50 with PIR and it'll be cheaper.

 

[dapperman]

Yes you can.
If you only have 50mm cavity you'd be better off using Celotex or similar- yes it's pricey but is a more effective insulator per mm of thickness (50mm PIR is about the same as 90mm rockwool). If you do use rockwool it needs to stop at the higher of the dpcs (and make sure you don't block air bricks)
If the wall you are building off has a working dpc then no you don't. Otherwise yes put one in.

as electrified said, i’m doing similar to this and need to know what cavity size and insulation to put in this, thanks.

 

[electrified]

Mortar doesn't stick to much. If you want to put a vertical dpc in crack on, just butter the bricks/blocks where they hit the dpc, it'll be fine.

If building control are involved you'll have no choice about 100mm cavity (or 150 in a few months). You'll get better thermal performance from 100 with bats than from 50 with PIR and it'll be cheaper.

That’s what i’ll do then, 100mm cavity with full fill rockwool bats, sound ok?.
Also when should i start to put these in? Above the dpc or on the dpc?

One more thing about a cavity fill, where you fill the cavity with concrete? Does this need to be done, and at what level to? And do you put an angle away from the inner leaf, if so how?

Thanks

 

[dapperman]

Mortar doesn't stick to much. If you want to put a vertical dpc in crack on, just butter the bricks/blocks where they hit the dpc, it'll be fine.

If building control are involved you'll have no choice about 100mm cavity (or 150 in a few months). You'll get better thermal performance from 100 with bats than from 50 with PIR and it'll be cheaper.

Hi, how deep would I need to did for my footing and how thick and wide does the concrete footing need to be. It will be a concrete block double skin wall about 2.2m high. I’m thinking to have the footing 450mm wide.

Thanks.

 

[oldbutnotdead]

Depth depends on local ground conditions, nearby trees etc, 700mm is about the minimum in firm clay. Can either be full fill or 200mm strip if you don't mind laying blocks in a trench
Width have 100mm of founds either side of yr wall (so if 100mm cavity,block and brick you'd want 500 wide).

 

[dapperman]

Depth depends on local ground conditions, nearby trees etc, 700mm is about the minimum in firm clay. Can either be full fill or 200mm strip if you don't mind laying blocks in a trench
Width have 100mm of founds either side of yr wall (so if 100mm cavity,block and brick you'd want 500 wide).

what do you mean by “either full fill or 200mm strip if you don’t mind laying blocks in a trench”. I’m thinking of having 100mm full fill rockwool for my cavity, where do i start this below above or on the dpc. Thanks

 

[oldbutnotdead]

Dig your trench to required depth.
Full fill means filling the trench completely with concrete to subfloor level. Strip means pouring 200mm depth of concrete into the trench and start your brick/blockwork below ground level.
Either way, you need to set the height of the concrete to the brick or block gauge (otherwise you will either be cutting blocks down or making up with some thick mortar courses).

 

[dapperman]

Dig your trench to required depth.
Full fill means filling the trench completely with concrete to subfloor level. Strip means pouring 200mm depth of concrete into the trench and start your brick/blockwork below ground level.
Either way, you need to set the height of the concrete to the brick or block gauge (otherwise you will either be cutting blocks down or making up with some thick mortar courses).

ah i get it, i will do a strip, 200mm seems a little small though doesn’t it? Also what are your thoughts about the rockwool question?

Thanks