Soundproofing semi: Opinions?

[mark482]

After much googling, reading, and a few quotes, thought I would try this one on all you helpful people

I recently moved in to my 1930's brick-built semi. Sound insulation is non-existent - I can hear everything from (the very nice) neighbours. When I say everything I mean TV, talking, doors closing, and... well you know, everything... The layout of my house is lounge at front, kitchen/diner at back and two bedrooms above all adjoining the party wall. The neighbours' house has had the ground floor knocked through and has an extension on the back i.e. one big room. Party wall is one brick (longest edge of brick, not quite sure of the terminology) with not great plaster on my side (finishing coat sound but undercoat pretty "sandy"), lots of missing mortar around the joists, don't know what it looks like under the plaster

Because the neighbouring house is rented and I can't count on the neighbours always being so reasonable (and because I'd rather not be so aware of their once-a-week schedule ), I've decided to put in some sound insulation.

This is what I decided is going to be the best option - willing to lose a little space from the rooms i.e. a few inches:

Make joists ground floor + 1st floor airtight i.e. fill holes around. Add rockwool between joists on 1st floor (to what depth from party wall?)

Adjacent to party wall i.e. lounge, bedrooms + kitchen: Build 2"x2" timber stud 1" away from existing party wall, attached to floor and ceiling only. Line with rockwool. Resilient sound bars on stud, two layers of 1/2" plasterboard, gap all around. Acoustic sealant around.

Loft: Seal party wall up to roof (expanding foam??) and make mortar good. Posisbly add e.g. rockwool-backed board to masonry. Line between joists with rockwool.

Use decent underlay + carpet lounge + bedrooms, possibly add board over current floorboards with some kind of insulation.

Still with me? (sorry for loooong post). Anything obvious wrong/missed/stupd ? I am a bit worried about spine walls + inner leaf of external wall (cavity, not filled yet) e.g. right now if neighbours are in front room of ground floor I can hear them very well from my front room 1st floor, and still hear from back room 1st floor.

Or... anyone recommend an acoustic consultant/someone who knows what they're talking about in the Leeds area?

 

[Nige F]

Just a suggestion gyproc metal drywall studding instead of timber ?...and acoustic board..all on their website, one to do myself so let us know how you get on

 

[freddiemercurystwin]

Unless you're proposing a specific insulation designed for sound insulation I'd see if you can opt for 50mm Isover APR 1200 (British Gypsum). Metal studs would be better as Nige F suggested because your timber studs will allow more sound through or look at the British Gypsum Gypframe GL1 Lining system. Not much point having resilient fixings if you've got a cavity which you should increase to around 85mm if you can afford the compromise in space. 2 layers of staggered 12.5 Soundblock (British Gypsum) plasterboard rather than normal plasterboard.

 

[Deluks]

You seem to have done the research and have it all sewn up. I'd agree about not using the resilient fixings, they are supposed to decouple the plasterboard from the shared wall, if you are already building a stud wall then this will already serve that purpose.
The extra benefits afforded by soundblock are much expensive for the slight increase in performance. Double 12.5mm standard will be plenty for domestic applications.

 

[mark482]

Thanks for the really helpful replies It seems to be so hard to get good advice on sound insulation - lots of companies selling rebranded british gypsum products and claiming "unique", + proprietary "miracle" products and lots of contradicting advice.

- I'll drop the resilient bars - I suspected that they were redundant, one of those companies I mentioned..
- I'll look into metal studwork properly - I was wondering if that might be easier, it looks affordable, and if it's better for the insulation great!
- Will go for the 50mm isover APR 1200
- I'll look into the soundbloc board, as Deluks said I think it is quite a small improvement for the price, at least according to specs on the web

A couple more questions if you can bear them...

- How important is the size of the cavity? Obviously this defines how much room I'm going to lose, and it's not the biggest at the moment! I read a few places 1" was ok. Am I going to regret this?

- The plaster on the party wall is pretty poor. I read that blown plaster can have quite an impact on the sound insulation. Given the space it is taking for no positive effect, should I consider taking it back to the brick and re-plastering, or possibly drylining, to get a bit of extra advantage?

- Any thoughts on the other walls - inner leaf of external wall and "dividing" wall on my side (neighbours have knocked through)? Plaster is bad on these - external one will probably be re-plastered from scratch, should I consider doing the other one too?

- Ceiling above is plaster and lath, probably going to boarded over as the plaster is really bad where cornice has been removed. Can I just lay isover on top of the laths between the joists, or should I put in a net/battens? Also, how far should I come from the party wall with the insulation - I would do the whole floor but getting the boards up is a real pain as they're t&g. Maybe it can be squeezed in from one end of the room?

Thanks again for the help, I hope this thread might be useful to everyone trying to find decent advice on this problem Will certainly report back how it goes...

 

[Deluks]

The total airspace includes any insulation, so if you have 3" stud placed 1" from the wall then you have a 4" gap from party wall to back of plasterboard. 4" is a sensible minimum.

True that missing plaster will give 'weak spots' It will be cheap to do if you do it yourself, and as it won't be seen the finish won't matter. Try and get a few bags of gyproc soundcoat and spread it nice and thick.

There will be no need to insulate the whole floor unless you are bothered about sound between your own floors.

 

[mark482]

Thanks, will work it out with 4" minimum.

True that missing plaster will give 'weak spots' It will be cheap to do if you do it yourself, and as it won't be seen the finish won't matter.

This had occurred to me - would be my first attempt at plastering and I imagine the finish would not be too impressive

 

[Reynardine]

Instead of rockwool, you might consider using slabs of material with a higher density.

If you google for "acoustic mineral wool slabs" or similar there are some vendors.

Slab Sizes are typically 1200mm x 600mm.
in varying thickesses e.g. 25mm, 50mm, 75mm and 100mm

 

[JohnD]

start with the cheapest bit, and fill all the gaps. this will mainly be round the joists but mortar joints may be poor and will be unplastered behind skirtings and between floors and in the loft. Hack out loose stuff and remortar. There may also be cracks as a result of subsidence and war damage. these may have been decorated over inside the rooms, but not out of sight. You can use plasterboard in the loft if the party wall is incomplete. Poke dense insulating bats between the joists to fill the gap against the party wall after you have repaired the joist gaps.

If there are, or were, fireplaces back to back, there may only have been half a brick between houses. If fireplaces still exist, check firebacks and (where you can) pargetting inside the flues which may be cracked.

If you put in built-in wardrobes against the bedroom wall, covering it completely, you will not need a false wall, and they will be useful. Hanging clothes inside will also absorb noises from

 

[tawelfryn]

Hack off plaster/render. Render with soundcoat, double dot and dab with plasterboard, bonding the boards.
Sorted.
All you have lost off the room is about 30/40 mm

 

[mark482]

Thanks for the suggestions.

- Will check density of rockwool vs. slabs
- Filling gaps is first on the list, boards up and working up the courage to open my can of expanding foam (some very deep gaps around joists) - I hear it can be a "dramatic" experience
- Irony of the wardrobe suggestion is that I've taken out a very extensive set of built-in wardrobes. They were pretty foul though - white MDF with fake panels painted...... orange (like the rest of the house, wish I'd taken some "before" photos, hoping the "after" will be better) - and the head of the bed was against the party wall. Like the icon though

tawelfryn have you experience of using two layers plasterboard over soundcoat? Losing less room is definitely appealing, but reading all the specs I could find (admittedly lab conditions not real life) I don't get the impression it would be as effective?

Maybe of use to others thinking about this, I have found this document very informative (Scottish Building Standards Agency):

http://www.arcamedia.co.uk/html/hsi.html

 

[Deluks]

The seperate wall is definitely the better option if the noise coming in is as bad as you describe. Dabbing board on will help cut out normal talking and other hi to mid frequency sounds but loud telly or music may still transmit.

 

[Reynardine]

open my can of expanding foam (some very deep gaps around joists) - I hear it can be a "dramatic" experience

If it's the canned foam I've been using then suggest maximum caution and respect for the stuff during use. i.e. wear goggles and gloves to protect your eyes and hands as it is seriously nasty stuff to get on you. e.g. iF the foam goes where you don't want it to , wait for it to dry ( at least 2 hours ) then remove it.

 

[Deluks]

Yeh, expanding foam, nightmare! Having said that it's very useful for gap filling, but not brilliant for soundproofing being light and not very dense.
Any big gaps should be filled with cut to size bricks and mortar. The foam can be used for smaller gaps though.

 

[tawelfryn]

tawelfryn have you experience of using two layers plasterboard over soundcoat?
http://www.arcamedia.co.uk/html/hsi.html

Its standard practice on Charles Church sites on apartments, albeit just 1 board thick dot and dab.
Soundcoat is excellent, if the noise is as bad as you describe then double board it, it will work. To be sure you could even use acoustic boards, which are slightly thicker.
If there is no firewall in the attic, build one, out of thermal blocks.
Fix another layer of boards to ceilings, (again acoustic if you like to make sure) over the laths and plaster,