OpenRent Community

House into flats convesion

Hello Landlords

Id really appreciate your help with this. You may have come across this when considering or developing a project.

There is a semi detached 80s build that has been converted to 2 flats, 2 separate entrances.
Its ceiling between the upper and lower flats (once the upstairs and downstairs of the original semi) have no sound reduction whatsoever. It is just as though someone is upstairs in a normal house.
My question is are there regulations that 2 separate dwellings must have some work done to ensure the dwellings barrier is safe? Heat and fire retention laws?

Many thanks

There needs to be an hours fire resistance between each dwelling What I do is this. … Plasterboard the ceiling and skim up. Fit rockwool fire and sound barrier in between the floor joists. Make sure all first fix electrics and plumbing is done. Lay boards back down. Use 8mm underlay and then carpet. Laminate is too noisy!

ps dont forget smokies and emergency light to hallway (put the latter in before you are told to)

Thank you for replying.
When you say need to do is it building regulations? and if so how would it be known it had been followed?

well do you know that your place had permission to be in two flats? Yes a place in two flats HAS to have fire protection. and dont you want to reduce sound at the same time? When I do a place up I make sure I leave inspection points so if anyone in authority asks what have you done I can easily show them . I also take photos

Hi Colin sorry I dont know if it had permission. I dont know how I would find out either. Nor about if the fire protection has been put in place.

Assume you have bought it? Your solicitor should have found this out (permission) .It will either be freehold or leasehold of course (long leasehold at least). I have bought both types . If you are also the freeholder you are in a good position but more resposibility. You can lift a floorboard up to see if any insulation is there. You need to investigate as if along the line it is inadequate then to remedy after is more costly.

That will certainly provide fire resistance with the right thickness of plasterboard, but simply adding rockwool between floor joist will not achieve the required decibel level reductions, particularly as any testing will be done without the carpet and underlay.

The gypsum plasterboard “White Book” details all the construction methods and ratings, well worth a look.

In our conversions we added a double layer of 12.5mm gypsum soundboard, fixed to a metal frame suspended ceiling grid on acoustic hangers, 100mm of rockwool over the ceiling grid retaining a 300mm minimum air gap to the underside of the floor. Then adding a floating floor on rubber isolating membrane on top of the existing floor boards, plus a fibre board underlay to laminate flooring. Our test results were the best ever produced in our area, outside of an organ factory with 300mm thick concrete floors, and exceptional considering it was a conversion of an old building. Because the laminate flooring is a hard surface, the tests were conducted on top of it, thereby including the additional layer of sound reducing fibre board underlay.
There are a few tricks to achieving these results including sealing up every gap around the perimeter of each layer of ceiling boards with silicone, as airborne sound travels like water. The airgap and acoustic hangers are needed to mitigate impact sounds.

I appreciate this may not be possible in regular houses with limited ceiling heights, we were lucky enough to have 11 foot high ceilings in the original buildings. There are construction methods to address the issue in properties with low ceilings, again detailed in the White Book.

You can cetainly go the whole hog . My coucil inspector was happy with what I had done in the limitations of the building

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Thanks guys for your replies.

Chris could you explain about the decibel level please?
And how would you find out if any tests were ever done?

Hi, decibel is a measurement of the level of airborne or impact noise, and are tested by organisations qualified to do so using specialist equipment.

The required levels of compliance are dictated by the government building control department / Approved Documents. If you are trying to check the compliance of an existing conversion, I would suggest you contact your local building control office to check the permission for that conversion, which should include noise test results and / or details of compliant construction.

If the property is a new build / purpose built Block of flats / maisonettes / terraces, I think they are excluded from producing actual test results, but they have to confirm compliance with the ‘Robust Standard Details’ for the construction of the relevant acoustic elements.

It’s quite a while since I did this myself, and requirements may have changed since then, but your building control officer will be able to guide you in this issue.

Glad to hear it worked out OK for you Colin.

Ours was a new conversion, so we had to jump through hoops to satisfy the building control department. We went the extra mile knowing tests were required, not wanting to risk marginal results. Also it means we have far less issues with noise disturbance from adjoining tenants, which I didn’t want to be sorting out forever and a day.

I did it all alone, with the help of my wife, to ensure the integrity of the installation. Not technically difficult but heavy work handling soundboard, which you will of course know being a joiner.

A building inspector told me fire resistant plaster board matches many sound reducing products . In US they use two layers of this plasterboard stuck together with a silicone like materal they call it green something look on u tube. Small air gap with vibration asorbing properties
Sound and fire resistance. Pack between joists with rock wool , factor in cables, underlay and carpet.
Mains wired linked fire alarms.

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V Useful not sure if been up dated though

Thanks for the link.

Chris 45 Doing the work yourself is always a good idea if you have the energy! All that sort of building work is heavy and labour intensive . But the satisfaction of a good job is great

Yes Colin, and amusing. Found my wife dangling from the MF ceiling frame, as she’d kicked over the ladder one time…

I sometimes wonder if it was the best approach, had I paid someone to do the work I could probably have built a portfolio twice the size in the same time, of course, with twice the debt! But at least I know it was done properly. The satisfaction and the pride, that is until the tenants move in…

I’ve discovered I can get almost as much satisfaction and pride from designing our retirement beach villa and apartments without barely lifting a finger towards the actual building work. Being an architect it’s all I ever really wanted to do, and with labour at £10/day and tradesmen (?) at no more than £20/day, there was no way I was getting my hands dirty at my ripe old age :slight_smile: However the frustrations of building on an island in Thailand have taken their toll… lots more grey hair and wrinkles. I can’t bring myself to put tenants or tourists in the apartments though, mentally disfigured for life with my UK letting experiences…

Yes it does, it’s all down to the density of the board and fire board & sound board are very similar.

The best method is to apply 2 separate layers with staggered joints to mitigate the passage of noise through aligned joints. And, as you say, an airgap is beneficial if you can accommodate it.

I don’t know about the US, but in UK carpet and underlay have to be removed for sound testing.

i ve never been asked to do any sound testing. Another point its really hard to stop sound travelling along floor joists in an existing building