plywood for partition wall

[sm_jamieson]

I am making a soundproofing partition just inside a bathroom brick wall, not attached to it, and to save space, the partition is to be solid 18mm plywood with no battens. Wall area is only about 2.5 x

2.5metres. I want WBP plywood, but I can see softwood and hardwood ply at very different prices. I need the plywood to be very stiff since no battening is involved. It also needs to be very flat, and to not warp or bend, since it will be tiled on. I may also clad with a cement board before the tiles. What's the best ply to use ? Good suppliers ? Cheers, Simon.

[Chris Bacon]

Hm. Not at all sure about that. What's on the other side of the wall? Won't a 2.5m square (how do you join it?) of ply act like a giant wobble-board?

[sm_jamieson]

Well, that is the question. I thought 18mm ply may be stiff enough, especially with cement board on the outside. I may use angle iron studs to stiffen it up. The requirement is for a "camden partition" only 50mm deep in all, in front of a normal 9" party wall. I could attach the partition with resilient bars, but that reduces the isolation. In actual fact, there could be a horizontal stud at a bit below bath height, since under the bath could be sound insulated differently. If 18mm ply is not stiff enough, is there any other board suitable ? Simon.

[Guy King]

The message from "sm_jamieson" contains these words:

That's taking quite a chance over a 2.5m span. Personally I'd get busy with the battens.

[Guy King]

The message from "sm_jamieson" contains these words:

Ah, right, now I see what you're trying to do.

You could get away with 3/4" ply if you could stiffen it. A welded steel frame would do nicely, 2" box round the outside, 1" angles running side to side, with some steel noggins welded in between, the whole thing screwed to the back of the ply.

Or - you could cut long strips of ply and glue then on edge to the back of the board - if you could stretch to making the whole thing 3" thick instead of 2, that'd stiffen it up a lot. Particularly if you ran them crisscross interlocking.

[sm_jamieson]

Thats the kind of idea. Edges will be screwed to battens anyway. Some kind of steel structure sounds a good idea. Cheers, Simon.

[Chris Bacon]

What's on the other side of the wall, that can be heard through 9" of it! A jet engine being tested?

[sm_jamieson]

You're curious now. Its partly an experiment, since I'm doing the bathroom back to brick anyway. I'm a bit paranoid about the odd noises you get from next doors bathroom, usually only audible a night. With a 9" wall, if someone is sitting on the loo right next to the wall and, coughs or blows the old nose, it can be heard. It unsettles me ! So I'm trying to make it totally silent. Thus a gap, some mineral wool, some heavy boarding etc. Bathroom not huge, so needs to be a slimline as possible. The jet engine ? Well, the overhead cistern I am removing does a fair impression of one. As an aside, my (to be removed) chinawear has gone rusty ! I cut the old cast iron bath into 3 with an angle grinder, and the iron dust that had landed on the damp sink and loo went rusty almost before my eyes, and somehow worked its way into the glaze. It can be removed, but with a lot of elbow grease. I tried cracking the bath with a lump hammer but nothing was happening, and the lady next door thought her time had come ! Simon.

[Guy King]

The message from "sm_jamieson" contains these words:

Can't you ask 'em to go easy on the beans?

I'd have thought most of the noise would come from the windows, anyway. Certainly what happens in our terrace - in warm weather when everyone's got their windows open you can hear bathtime gurgles all over the place.

[Pete C]

Hi,

Why ply? It's very strong but not that stiff, or dense. Something heavy like moisture resistant MDF or a cement board like Fermacell should be better. If space is tight a layer of heavy rubber like stable matting could be used to damp vibration and resonance.

Check out what high end speakers are made out of, ply would be the last material to use. Plenty of info on soundproofing out there on the web too.

cheers, Pete.

[dg]

Use Fermacell board for soundproofing, rather than messing about with trying an unconventional ply construction.

dg