Soundproofing noisy joists

[russy47]

Hi,

My property is 1920's Town/terrace era.
The walls are solid brick and the joists run through into adjoining properties.
This can be seen in my cellar and also heard! Sound from next door both ways is clearer in the cellar along the joists.
Im wondering if there is a way to plug or cut the joists to prevent the sound/vibration travelling along them without affecting the integrity of the joist.
Obviously any cut would be where the joist sits on the wall if accessible.
But could something be attached or drilled into the joists and plugged to deaden the noise travel??

I also am considering the alternative option of sound proofing and rubber type layers between these joists and wooden flooring on the the room that sits on these joists but would prefer to tackle the problem at the root.

Its a bit of a technical querey but any thoughts much appreciated!

regards

Russ

 

[Deluks]

The gaps around the joist are a common problem for airborne sound and can be filled with bricks/roof tiles and mortar.

Actual vibrations are caused by structural borne sounds and you will need to decouple the joists from each other, and possibly the wall as well, at least on one side.

If access from beneath is good you could possibly replace the joists with new ones in between, which could be fixed to the wall with bolt on hangers, then the existing joists could be cut (and possibly trimmed to the new ones.

Obviously you should match the quantity and size of the existing joists.

What sort of noise are you having to deal with here?

 

[russy47]

Hi Deluks,

The noise (sound as if) comes through the adjoining walls. Mainly voice noise and footsteps on hardfloors. Cant be specific ie low frequency. But I know that part of this is coming through the floor and joists due to the increased volume in the cellar.

Excuse my ignorance but can you translate some of your terms. Decouple I presume just means detach or cut where it goes into next doors.

'Fix to the wall with bolt on hangars'?

Im new to this so just trying to visualize what you mean.

Access is quite good in the cellar.

 

[Deluks]

Hi Deluks,

The noise (sound as if) comes through the adjoining walls. Mainly voice noise and footsteps on hardfloors. Cant be specific ie low frequency. But I know that part of this is coming through the floor and joists due to the increased volume in the cellar.

Excuse my ignorance but can you translate some of your terms. Decouple I presume just means detach or cut where it goes into next doors.

'Fix to the wall with bolt on hangars'?

Im new to this so just trying to visualize what you mean.

Access is quite good in the cellar.

Decouple meaning not touching, so yes cutting joists.
Joist hangers are metal cradles that can be bolted to the wall to support the ends of joists.

Are there any gaps in the wall around the joists? Not unusual to see big gaps where the joists slot into the wall. A common problem in older properties.

 

[russy47]

Ok got you now... yes i think there are gaps around the joists in many cases.

So these hangers... can they actually handle the weight and do the same job as the joist suspended on solid wall?!
I can just imagine the metal bending over time??

 

[Deluks]

Yes they are strong enough to carry a joist, plus however much floor loading the joist is carrying. This is a big job, and without sounding patronising you don't sound as though you have enough experience to carry it out.
It is a last resort though, actually forget I mentioned it

Get those holes completely filled and you'll likely solve the problem.
Shopping list: Some old bricks, some old roof tiles, a bag of readymix mortar and a trowel.

 

[russy47]

Ha is it that obvious! Your damn right I haven't got the experience but I'm very interested in possible solutions andclike to know what I'm talking about if I need to get someone to do the job.

But yes your right I'll be filling any gaps which I'm happy to do on my tod.

And may end up just soundproofing under the floor above these joist as decoupling foes sound tricky and costly

 

[Deluks]

If you have old gappy floorboards then fixing hardboard or similar up against them from beneath will seal those gaps too.
Then stuff some rockwool type insulation between the joists, loft insulation roll on chicken wire work well, then you have the added bonus of heat insulation for your ground floor as well.

 

[parakeet]

If you have old gappy floorboards then fixing hardboard or similar up against them from beneath will seal those gaps too.

Is expanding foam a viable solution to fill any gaps at that point?
Wouldn't more wood just mean more sound travel?

Then stuff some rockwool type insulation between the joists, loft insulation roll on chicken wire work well, then you have the added bonus of heat insulation for your ground floor as well.

Should some insulation be laid *around* the joists, to dampen sound?
Can you explain the insulating effect of laying insulation flat on chicken wire, *between* the joists, as though it were for heat insulation?

Thanks.a

 

[cjard]

Can you explain the insulating effect of laying insulation flat on chicken wire, *between* the joists, as though it were for heat insulation?

Thanks.a

chicken wire stops the insulation falling out

 

[parakeet]

Can you explain the insulating effect of laying insulation flat on chicken wire, *between* the joists, as though it were for heat insulation?

Thanks.a

chicken wire stops the insulation falling out

Thanks, but I meant...
By laying on chicken wire *between* the joists, how will that dampen sound travel? Shouldn't it somehow be wrapped *around* the joists?
I can see why *between* would help temperature insulation, but how sound?