How to solve soundproofing challenges?

[Gorbstein]

Help!

Picture this : 1910 semi, party wall merely a single skin of brick and plaster, empty external cavity walls, and shared floor joists which run across the two dwellings. Bedrooms and sitting rooms meet at the party wall.

Couple it with very loud dogs and a TV next door and you can probably understand my frustration. However, I have just moved in and so cannot sell for quite some time. I also prefer not to shoot the dogs, shoot the owners, or shoot myself.

So, I'm really hoping there is a positive soundproofing solution to all of this. It may take time and money, but I am prepared for that.

Challenge #1: Party wall. As I said, this is a single skin of brick directly plastered (no lath). There are also door architraves meeting the party wall upstairs, giving about 50mm (possibly 55mm) to play with. Downstairs I have some beautiful cornicing which I desperately want to keep, giving me roughly the same 50mm approx to play with. In all other rooms I have lots of space to burn. What would be the best solutions?

Challenge #2: Shared floor joists through party wall. Even in the back rooms I can feel/hear next door walking around. The floor actually bounces in my property. I also expect this is a prime cause of flanking noise. Can these joists be cut and supported another way? Or is there some way of deadening sound travel?

Challenge #3: Cavity walls : a huge source of flanking. With an earplug in one ear and the other to the external wall, I reckon I could hear my neighbours dog fart. Would standard cavity insulation help? Or would it need to be some acoustic insulation to fill the gap?

Yours, desperately,

D

 

[simonjay]

Help!

Picture this : 1910 semi, party wall merely a single skin of brick and plaster, empty external cavity walls, and shared floor joists which run across the two dwellings. Bedrooms and sitting rooms meet at the party wall.

Couple it with very loud dogs and a TV next door and you can probably understand my frustration. However, I have just moved in and so cannot sell for quite some time. I also prefer not to shoot the dogs, shoot the owners, or shoot myself.

So, I'm really hoping there is a positive soundproofing solution to all of this. It may take time and money, but I am prepared for that.

Challenge #1: Party wall. As I said, this is a single skin of brick directly plastered (no lath). There are also door architraves meeting the party wall upstairs, giving about 50mm (possibly 55mm) to play with. Downstairs I have some beautiful cornicing which I desperately want to keep, giving me roughly the same 50mm approx to play with. In all other rooms I have lots of space to burn. What would be the best solutions?

Challenge #2: Shared floor joists through party wall. Even in the back rooms I can feel/hear next door walking around. The floor actually bounces in my property. I also expect this is a prime cause of flanking noise. Can these joists be cut and supported another way? Or is there some way of deadening sound travel?

Challenge #3: Cavity walls : a huge source of flanking. With an earplug in one ear and the other to the external wall, I reckon I could hear my neighbours dog fart. Would standard cavity insulation help? Or would it need to be some acoustic insulation to fill the gap?

Yours, desperately,

D

There are lots of posts on this forum about party wall soundproofing (general principles: mass, isolation, avoidance of air paths), so I'll not repeat it all again. But specific points about your case:

Party wall - 9" thick solid wall plastered directly is very common up to the 1930s. A common method is to build a isolated stud wall with 2 sheets of plasterboard but the improvement is variable - you cannot do much in 50mm. If the wall is thinner sound penetration will be worse.

Shared joists are bad and air leakage around them is likely (maybe under the floor). If the floor bounces from next door there almost *must* be some gaps ! You can check for this and close up any gaps with expanding foam or mortar. Ideally the joists would be separated, but this might affect next door if the bearing on the party wall is poor. Ideally they would be cut back to half way through the partly wall and bricked off, and your joists offset so there is no chance of them touching. Best of all to have your joists running from front to back and not touching the party wall at all. Downstairs you could put in a solid floor.
Taking it to the extreme, I heard of someone who built a new brick skin creating a cavity wall and supported his joists off that, but then new foundations might be required, and a lot of space is lost.

Cavity walls. If there is sound leakage into the cavity (dodgy air bricks, etc), this could be an issue. Cavity wall insulation might have the side effect of sealing air gaps, and could help absorb the sound. There is no special acoustic insulation for use in cavity walls.

Summary:
Check for air leakage first, then deal with the shared joists (the 2 might be related). Then consider isolated stud walls.
Make sure you check under the floors and in the loft. Some of these houses had a common floor void or roof space, and the sound comes straight through.

Unfortunately the results are hard to predict and often disappointing. We'd all like to like in detached houses !

 

[Gorbstein]

Wow, brilliant response. A mine of information. Thank you.

I forgot to mention I had previously searched for soundproofing on this forum, but couldn't find a thread that specifically mentioned the combination of soundproofing the wall and underfloor at the same time. I didn't want to spend a fortune on a false wall then break any seals by having to go back and do underfloor.

I am going to tear up a few floorboards this weekend and see exactly what the situation is with the joists.

I was just quoted roughly £1k per room to add a stud wall filled with heavy acoustic insulation and two layers of acoustic plasterboard. I was also told the wall cavities could be drilled and filled with some kind of acoustic insulation. Going to get quite a few more quotes methinks..

 

[simonjay]

Wow, brilliant response. A mine of information. Thank you.

I forgot to mention I had previously searched for soundproofing on this forum, but couldn't find a thread that specifically mentioned the combination of soundproofing the wall and underfloor at the same time. I didn't want to spend a fortune on a false wall then break any seals by having to go back and do underfloor.

I am going to tear up a few floorboards this weekend and see exactly what the situation is with the joists.

I was just quoted roughly £1k per room to add a stud wall filled with heavy acoustic insulation and two layers of acoustic plasterboard. I was also told the wall cavities could be drilled and filled with some kind of acoustic insulation. Going to get quite a few more quotes methinks..

If there is some acoustic insulation that can be put in the cavities, make sure that it is also suitable for external walls and will not let moisture through. And acoustic insulation will be denser than normal cavity wall insulation, so will not be as good as keeping the heat in !

 

[tony1851]

Is your house original, or has it been subdivided vertically since 1910? It seems unusual for a house of that age to have a one-half brick thick party wall; similarly, most speculative houses built before 1914 tended to have solid 9" walls rather than cavity walls.

 

[themiddleagedun]

A few old terraced houses here in Lancs have a 1/2 brick party wall. they're as much use as a chocolate kettle.

I've never heard of the joists running through from one house to the next though.. Sounds like you're "up against it" Good luck.