Insulation

eeiifn

Hi,

I am in the process of insulating between the ceiling downstairs and the floor upstairs (10 year old dormer). Initially we never insulated this but have found it very noisey. We are using 140mm rockwool flexi, I'm just wondering would it be a good idea for noise reduction to put two layers of
insulation in? Probably won't fit 2 layers of 140mm but could use a top layer of 100mm rockwool roll on top of the flexi? Plan to put down solid timber floor on top of the OSB boards? Does any know if this would be
a waste or a good idea??? Thanks and any other tips on the best way to sound proof would be much appreciated...

Slig

eeiifn wrote: »

Hi,

I am in the process of insulating between the ceiling downstairs and the floor upstairs (10 year old dormer). Initially we never insulated this but have found it very noisey. We are using 140mm rockwool flexi, I'm just wondering would it be a good idea for noise reduction to put two layers of
insulation in? Probably won't fit 2 layers of 140mm but could use a top layer of 100mm rockwool roll on top of the flexi? Plan to put down solid timber floor on top of the OSB boards? Does any know if this would be
a waste or a good idea??? Thanks and any other tips on the best way to sound proof would be much appreciated...

The best sound proofing would be 2 different density materials to absorb different sound waves. More important than that would be to ensure there is plenty of bracing between the joists. The reccomended is 1.35m intervals but really its the more the merrier.

eeiifn

The best sound proofing would be 2 different density materials to absorb different sound waves. More important than that would be to ensure there is plenty of bracing between the joists. The reccomended is 1.35m intervals but really its the more the merrier.

Hi Slig,

Thanks for replying, I'm not well up on this so would like to get it right second time round. Could you explain what you mean by "ensure there is plenty of bracing between the joists"? What is bracing?? Are these the little boards?? They are probably about 5 or 6 foot apart maybe more - I notice there wasnt many of them when I took up the floor? Would you recommend putting more of these in now? Would this improve things? Also what would "2 different density materials" be - Sorry I'm not well up
on this at all............ thanks for the help...

Slig

I'm trying to remember my college years, as far as I can remember for sound insulation different densities of materials will absorb different ranges of sound.
Regarding the bridging, its the smaller pieces of timber that brace the joists, there are usually only 3 or 4 between every joist. The more bracing is in your floor the more solid it will be and the less movement will occur.

davgtrek

there are 2 types of noise to deal with. airbourne ( the telly in sitting room or metallica in the bedroom ) and impact ( stilettos on the first floor ).

the rockwool will help a lot on airbourne and heat insulation. pack in as much as possible anyway as its relatively cheap.

it sounds like you will be re-flooring upstairs. in this case i would suggest that the buildup of layers from room to joist is as follows.

1 whatever timberflooring you wish on top of
2 standard thickness 12.5mm plasterslab. This is excellent at absorbing sound, is easy to lay and vut in sheets and is very very cheap. compare its cost versus any proprietary rubber based acoustic matting and you will see.
on top of
3 OSB boards as planned.

Obviously swap the plasterslab & osb boards in areas under tiling ( wet areas ) for marine ply.

I have this buildup in my own house and its very effective acoustically.

in hindsight I would not put the rockwool quilt insulation in the floor under any wet areas. if theres a leak its not great stuff. i would leave it out there.

in the old days ( 50+ years ago in now listed properties etc. ) they used to use sand in between joists. excellent acoustic properties and very cheap.
heavy though.

good luck.

p

eeiifn

Thanks Davgtrek and Stig for the replys......

So the plan is to put some more braces between the joices to make it more solid and then fill the joict to the top with insulation, (is it necessary to leave any cavity at the top of the joict - next to the OSB board?? or can it just be filled up completely with insulation)
The OSB board then goes on top....
Davgtrek, do you nail down the plasterboards? (these are boards that
are paper either side with what looks like chalk in the middle?? Am I right?)
As the joict is now covered with OSB how will I know what to nail the plasterboards to? I plan to lay a solid oak floor on top, if I go for the plasterboards do I still use an underlay with the oak floor?

Thanks again for all the advise.............

davgtrek

you can fill the depth of joist with insulation or leave a small bit at top. that doesn't matter. whatever 1 thick or 2 thin rolls gives you.

no need to nail plasterslab ( yes the ordinary paper with chalk in between ) buy you would need to mark on it with a marker where the joists are if you want to nail thru to joist. acoustically clipping the floorboards and using as little nail through to joists as possible would be better. a floating floor as such.

only reason for underlay under floor boards is to give some effect of a real timber ( bit of give ) and to absorb small abnormalities in surface of floor. this is not needed for a first floor as you feel the hollowness anyway and it will have some give/spring.
it wont feel like floorboards glued straight to concrete floor.

MAKE SURE OSB boards are SCREWED down. maybe leave a slight gap 1mm rather than butting them tight to each other. If they have a T&G your're grand anyway.
Otherwise you get the squeaking when walking over the floor, though with the plasterslab on top it will spread the point load of foot but in case.

the squeaking is the boards rubbing against each other.

good luck with it

p

Carlow52

OP sound is carried by air so if u have any recessed lighting in the ceilings this will reduce the efficiency.

RKQ

Good advice above.
Double slabbing the ceiling will also greatly improve sound proofing. Use a resilent bar between slabs to decrease vibration sound.

19mm plasterslab on metal tophats, on joist is good especially if you have "height" issues and don't want to plane bottom of doors. Or re-hang all existing 1st floor doors.

Layers under or over joists will greatly improve sound insulation.

eeiifn

Thanks all for the advise..... spent the weekend putting in extra bracing between the joists and it seems to make a bigger difference so far...... much more solid to walk on and alot less vibration.......

RKQ can I just check with you what a resilent bar and metal tophats are? The work is all DIY so not familiar with this.... Thanks again...