50mm Rockwool in cavity wall not 100mm

[theDIYkid]

Hi lads
Can I use 50mm or 75mm in cavity walling and not use the 100mm, its a small music room extension and trying to cut back in costs? 100mm fully fills the cavity I know but would it be k to not totally fill it.
Thanks
S

 

[johnny2007]

The difference in price is very marginal considering it's your house.
Invest a little more and you won't regret it.
Otherwise you could have a 50mm cavity and the bricklayer will curse you for a good time.

 

[theDIYkid]

The difference in price is very marginal considering it's your house.
Invest a little more and you won't regret it.
Otherwise you could have a 50mm cavity and the bricklayer will curse you for a good time.

Thanks, t works out about £12 more perpack for 100mm and then there is less slabs too for coverage, is there anything else I can use cheaper than rockwool at 100mm for the cavity. I intend to also put 50mm acoustic sound slabs on the inside of the build.

 

[johnny2007]

How much more is it overall?

 

[theDIYkid]

How much more is it overall?

About £100 more the 80mm with 8 slabs is £29 and the 100mm with 6 slabs is £43

https://www.ebay.co.uk/itm/Rockwool...c10&&&&&&&var=471490055194&varId=471490055194

 

[noseall]

trying to cut back in costs?

Seriously?

Skimping on the insulation is the last thing you want to do. Next you'll be asking if its ok to halve the cement quantities or leave out every other course of roof tiles.

 

[johnny2007]

The difference in price is very marginal considering it's your house.
Invest a little more and you won't regret it

I stand by my first comment

 

[pilsbury]

By even my penny pinching standards this is daft.

 

[cdbe]

See if you can get some 75mm Dritherm 32 from B&Q - cheapest you will get and it's performance is not far off standard 100mm batts, however it won't quite meet the regs with standard brick/block construction (but may if your acoustic insulation has any thermal properties, but you'd have to prove it).

 

[Tigercubrider]

Don't skimp on acoustic rockwool

 

[theDIYkid]

Ok thanks a lot for feedback and the *******ing I will stick with 100mm Rockwool cavity in the 100mm cavity between the 2 skins, assuming I push into place as its a 100mm into 100mm, also then I will add 50mm internal on the inside walls then plasterboard.
Thanks

 

[big-all]

my freind built his summerhouse and used 75mm rockwool all round so he could practice drumming in it
he was thoroughly disappointed when i walked past the back in the next door back garden talking to someone and the conversation was easily heard
off course i pointed out sheet material and a frame backed with sheet material and cladding was a good sounding board

 

[Tigercubrider]

To avoid the sounding board, build a timber frame that sits on neoprene inside the brick structure . Do NOT fix it to the brickwork. Fill the timber frame with rockwool and plasterboard it. Ideally two layers of PB. Use filler on all PB joints- Skim.
The idea is two independant boxes - one inside another- with no mechanical fixings breaching the gaps

 

[theDIYkid]

cool thanks for the tips will go down that route internally.

 

[noseall]

assuming I push into place as its a 100mm into 100mm

It is built in, not pushed in and fits between the tie wires.