Cavity width tolerance

[23vc]

Hi
My cavity brick and blockwork is supposed to have 100mm cavity but in places it varies a bit, going up to 120mm Max. I guess this is because I've not got my inner skin bang on despite my best efforts. Just wondering how big an issue this is and whether I should redo it?
I'm using 100mm dri therm 32. Any thoughts welcome

 

[Doggit]

How are you intending to skim the inner wall. You could take some of the wave out with dot and dab, otherwise you'd need to bond the wall to straighten it. So how much work to redo the inner skin, and how come you weren't using a string line to keep you steady.

 

[noseall]

If it is a two storey jobby you can correct this after the first floor joists. If single storey, use the external brickwork as a checking datum when lining up your wall plates as it will be the external relationship between the rafter ends and the last visible course of bricks that will be affected by any cut rafter ends.

 

[23vc]

Thanks. To be honest I'm not bothered about it affecting the plastering as I can fix it with dot and dab, I'm not even sure what's gone wrong as its fine in most places. I was more concerned that it invalidates the insulation by having a slight air gap in places.
I will carry on and take more care as I go up to ensure the cavity is spot on 100mm.
Noseall when you say fix it after the first floor joists is that so it's not noticeable within a room?
Thanks

 

[noseall]

Noseall when you say fix it after the first floor joists is that so it's not noticeable within a room?

Yeah, it's just an ideal place to hatch the blocks back and re-set the gap. Incidentally, you need a 110mm cavity gap just to accommodate some of the more 'springier' cavity insulation batts.

Some of the fishy smelling earlier yellow stuff was quite well behaved. The latest brown mottled (better smelling) recycled stuff is pants.

 

[23vc]

Great, that's put my fears to rest then, cheers. Yeah I'm using the brown stuff, and cutting it with a saw (is there a better way?)
Thanks again

 

[noseall]

Great, that's put my fears to rest then, cheers. Yeah I'm using the brown stuff, and cutting it with a saw (is there a better way?)
Thanks again

Sharp Stanley knife over a piece of wood or several slashes with a brickies trowel on the site floor.

 

[23vc]

Thanks v much

 

[garyo]

Incidentally, you need a 110mm cavity gap just to accommodate some of the more 'springier' cavity insulation batts.

I've made that mistake. With the yellow stuff on a small porch I had to lean pieces of lumbar up against the blocks as I bedded them to keep the insulation from pushing them back out. Complete pain. Glad it was only small and single-storey.

 

[^woody^]

Are the ties suitable for a 120mm cavity?

 

[^woody^]

With the insulation, keep it compressed right up until it's going in the wall. Built up part of the leaf and then slot a row of the insulation in

 

[JohnD]

the brown stuff I've used is treated to prevent it shedding irritant dust and fibres. I've found it so much better in this respect that I would never touch the yellow again.

You can cut it with wallpaper shears or a carving knife, or (on the roll) a panel saw. It is easier when compressed.

 

[23vc]

Are the ties suitable for a 120mm cavity?

They're 225mm so I guess not. I'm planning on fixing it though, it's only 120mm in the odd place. It's generally more like 100-110. Good point though, I need to pay more attention!

 

[noseall]

With the insulation, keep it compressed right up until it's going in the wall

We used to slit the bale so that you could pull out individual batts through a central hole whilst the perimeter of the plastic wrapping stayed put and kept the bail intact and mostly compressed.
However, the newer recycled brow stuff likes to fall apart along its layers and you end up leaving part of your batt behind.
We end up now having to slit the bale open to retrieve the individual batts. Difficult to maintain compression overnight with an open bale.