Soundproof the shop floor

Most of the rooms in the flat I am using Gypsums Silent Floor system which I have been doing myself, see this blog from 2 and a half years ago. https://www.korfi.co.uk/gypsum-silent-floor-part-2/

For the room above the shop though I can’t really do that because of the number of partition walls on top of full width floorboards. So, I need to soundproof from the room below.

For this work I decided I would invest money in a company who specialise in providing sound reduction solutions. To meet building regulations you have to show that you can reduce both impact noise (people stomping about upstairs) and airborne noise (that music is on full blast again).

For me, that is 43dB for airborne noise and 64dB for impact. There will however be some leniency on that figure as they will take into account the house is 120 years old and has a great big chimney stack in the middle of the house.

There will always be an element of flanking noise so you should also think about that. In the shop all the walls have timber cladding and that will be my biggest culprit of flanking. As I didn’t want to remove all the timber, the next best thing would be to remove the coving, and the top 150mm off the cladding. That way the sound boards can butt closer to the wall, blocking of the sound waves travelling up and behind the cladding.

I haven’t measured what the current noise reduction is, but as I can just about hear every conversation in the shop from the room above lets say it is somewhere between 0 and 5dB

The tops need to be cut with a circular saw. To do that safely best to have scaffold boards on top of trestle tables. I have two trestle tables but no scaffold boards. To save money I decided to make my own out of the remaining leftover OSB3 boards.

I cut them into strips then bolted together to get lengths of 3.9 mtrs.

However, at that length across just 2 trestles it was too bouncy for me, so I just stood and watched!

I got two more trestles so I could use them.

With that done I was ready for the sound proof team to do their thing.

Sound absorbing brackets are fitted to the ceiling joists so that a framework can be suspended from it.

At this point I realised my first mistake. We hadn’t cut off enough of the cladding. 200mm would have been better, although now in hindsight I should have removed the cladding completely. Flanking should still be reduced, but not as much because it is now going up behind the ceiling rather than under it.

With the grid system complete, 100mm Rockwool RWA45 is installed. This insulation is to combat airborne noise.

Looking from the outside you can only just see the ceiling when looking at the top window. Not as much as I thought is showing which is good. Although it would have been better if the board was painted black.

Oooops……..

With the insulation in place, the first layer of Gypsum Soundbloc plasterboard is fitted.

Next it is time for the magic ingredient – Green Glue. This is sandwiched between the second layer of SoundBloc.
This glue is expensive and you need about 2 tubes per board. The aim of the glue is too reduce impact noise.

Final step, the ceiling is skimmed.

Time will tell if keeping the cladding is going to be a problem.

It’s going to be difficult to remove it now without damaging the ceiling. But to get a very rough idea of the airborne noise I cranked up Planet Rock on the radio and measured the decibels.

It fluctuated around the 76 / 77 mark. I then went up into the room above and measured.

I could hear the radio but it was muffled. The reading fluctuated around 33 / 34.
Which is a 43dB reduction. I doubt that’s how a proper sound test is done, but it is encouraging. Once I have underlay and a carpet upstairs it will be better. I haven’t measured impact noise.

The room next to shop, where I had the staircase, I decided to take down the lathe and plaster ceiling and have that redone. Because I am applying the Silent Floor system above, it doesn’t need the same thing.

Just two layers of Soundbloc with green glue between.

The final area that needed treatment was the alley that is under the bathroom and bedroom. This also has a suspended grid system and rockwool.

It does have the same 2 layers of soundbloc and glue, and the edges sealed with acoustic sealant.

But, as this is outside, it needs a different finishing material otherwise the boards will get damp and mouldy. This isn’t done yet, but will either be cement boards, or rendered with cement & sand over chicken wire mesh fixed to the boards.

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