Sound proofing under floorboards solution?

cem

We have creaky floorboards so replacing/re-screwing them to stop the creaking. Also want to take advantage and stop sound coming upstairs through the floor.

I would deeply appreciate any recommendations for what could be used under the floorboard AND over the floorboards.  Budget is an issue as can't spend too much on it.

Many thanks in advance

tacpot12

Rockwool Sound Insulation Slab under the floorboards; currently on offer at Wickes Rockwool Sound Insulation Slab - 100 x 400mm x 1.2m | Wickes.co.uk
For over the floorboards, you want a good quality rubber (not PU foam) underlay. You need mass to deaden sound, so the heavier the better. Something like this: Duralay Lifestyle 130 Carpet Underlay - Tradepriced Carpet Underlay
Note that Tradepriced underlays have a sound reduction rating but this is an impact rating, so only relates to noise traveling down through the floor when you drop something upstairs. 

cem

tacpot12 said:

Rockwool Sound Insulation Slab under the floorboards; currently on offer at Wickes Rockwool Sound Insulation Slab - 100 x 400mm x 1.2m | Wickes.co.uk 

Thank you.  is the following the same thing as the one you;ve mentioned?
https://www.building-supplies-online.co.uk/rockwool-rwa45-acoustic-insulation-slab.html

Jeepers_Creepers

Hi Cem.

Is this air-borne sound or through the fabric of the building? If the former, then I'd suggest the most important thing is to absolutely close off every teeny gap. If you use these insulation slabs, they'd need to be snug and tight against the joists, and also sealed at each end where they meet the walls.

Something I did in my hallway when I renewed the T&G flooring was to lay 8mm-thick laminate-underlay fibreboards over all the joists first, frame-sealanting them together and especially around the perimeter where they butted to the walls. I then laid the new T&Gs on top. I did this mainly for draught-proofing (and added thermal insulation), but it would also have helped sound transmission if it had been an issue.

It's a bit like a double-glazed window which has a dodgy seal - the higher frequency sounds from outside (birdsong, tyre swish, stuff like that) comes through clearly even tho' the windows themselves block off pretty much everything. It's the same with sound transmission between attached houses and flats - and gap in a side wall under the floor will act as a path.

So, if I was concerned about noise transmission, in addition to adding the 'proper' stuff under the floor, I would also lay a complete layer either immediately under or even over the flooring, sealed as I said before.

Is all of this within your own home, or are you living above someone else?

tacpot12

cem said:

tacpot12 said:

Rockwool Sound Insulation Slab under the floorboards; currently on offer at Wickes Rockwool Sound Insulation Slab - 100 x 400mm x 1.2m | Wickes.co.uk 

Thank you.  is the following the same thing as the one you;ve mentioned?
https://www.building-supplies-online.co.uk/rockwool-rwa45-acoustic-insulation-slab.html

They aren't quite the same thing. Rockwool's website doesn't have the information to say exactly how they differ, but it is likely that the Wickes product is slightly less dense although both will be around right density to produce the best sound reduction that can be achieved with mineral wool. The biggest difference might just be the packaging and the minimum order quantity. The RWA45 product tends to be sold in bulk from builder's merchants and will have a minimum order quantity, whereas, the Sound Insulation Slab is sold via retail outlets and you can by just one if that is all you need. Check the width carefully. The link you supplied was for a 600mm wide slab, whereas the item at Wickes is 400mm wide. The other difference is the density of the Wickes item is lower at one edge to allow you to squeeze into a space that is slightly too narrow for it. Rockwool call this their FlexEdge. The RWA45 doesn't have this because it is designed for buildings that are built to higher tolerances.  

cem

Jeepers_Creepers said:

Hi Cem.

Is this air-borne sound or through the fabric of the building? If the former, then I'd suggest the most important thing is to absolutely close off every teeny gap. If you use these insulation slabs, they'd need to be snug and tight against the joists, and also sealed at each end where they meet the walls.

Something I did in my hallway when I renewed the T&G flooring was to lay 8mm-thick laminate-underlay fibreboards over all the joists first, frame-sealanting them together and especially around the perimeter where they butted to the walls. I then laid the new T&Gs on top. I did this mainly for draught-proofing (and added thermal insulation), but it would also have helped sound transmission if it had been an issue.

It's a bit like a double-glazed window which has a dodgy seal - the higher frequency sounds from outside (birdsong, tyre swish, stuff like that) comes through clearly even tho' the windows themselves block off pretty much everything. It's the same with sound transmission between attached houses and flats - and gap in a side wall under the floor will act as a path.

So, if I was concerned about noise transmission, in addition to adding the 'proper' stuff under the floor, I would also lay a complete layer either immediately under or even over the flooring, sealed as I said before.

Is all of this within your own home, or are you living above someone else?

Thank you for your reply.  
Did you use something like this over the joists?
https://www.builderdepot.co.uk/fibreboard-7mm-underlay-8-59m2
when you say frame-sealanting - you did in between the fibreboards - right (sorry I know might be a basic question but just want to be sure)
and then something like this, over the floorboards? : 
https://www.builderdepot.co.uk/timbertech2-acoustic-plus-gold-5mm-underlay-8m2-roll
Thank you so much in advance

cem

tacpot12 said:

cem said:

tacpot12 said:

Rockwool Sound Insulation Slab under the floorboards; currently on offer at Wickes Rockwool Sound Insulation Slab - 100 x 400mm x 1.2m | Wickes.co.uk 

Thank you.  is the following the same thing as the one you;ve mentioned?
https://www.building-supplies-online.co.uk/rockwool-rwa45-acoustic-insulation-slab.html

They aren't quite the same thing. 

Thank you. You have picked up on some great points. The Width, the soft edges, density etc.
Do you know if there are any cheaper alternatives to Rockwool? Thanks again