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I'm building two stud walls joining at a right angle to create a small room in the corner of a larger room. The timber I'm using is 63x38mm (2 1/2" by 1 1/2" - actual measurement) CLS. One wall is 2.4 m long, the other wall with the door is 1.8m long.

Now looking at the soundproofing solution I have in mind I wonder if these studs will be strong enough to support the wall. Can anyone advise on the strength of such a structure with 40 or 50cm centres? The walls are not loadbearing.

Heaviest case, the wall layering will be: Soundboard | Stud wall (40cm centres) | Soundboard | Rubber panels on which are suspended: | Soundboard | Soundboard

An alternative layering would be | Soundboard | Stud wall (50cm centres) | Rubber panels on which are suspended: | Soundboard | Soundboard

The soundboard is heavy sound resistant plasterboard which weighs 28kg for 2.4m by 1.2m.

The rubber panels weigh 15kg for 1m by 1m

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  • What is the reason for not using traditional dimensional 2" x 4" lumber for the studs ? This would allow you to put thicker sound proofing materials inside the wall as well. – Alaska Man Apr 17 '20 at 18:41
  • @AlaskaMan I rushed into this project as our home got too small for the people living in it during confinement. I initially planned to go for the thinnest wall I could to save space, then soundproofing was an afterthought. As it is, I've done half the studwork already, which I'd like to keep, so I'm thinking on whether to downgrade the soundproofing to lessen the structural load or not. I am also planning to use acoustic rockwool inside the wall. – Sterl42 Apr 17 '20 at 21:36
  • This is definitely the “weak link” case. No matter what you do, the weak link will be at an opening...like at the doorway, windows, if any, and light switch or outlets. There’s a special way of solving this problem, depending on what your STC rating is... – Lee Sam Apr 17 '20 at 23:17
  • What is the span of the studs? (Unsupported height of wall.) – Lee Sam Apr 17 '20 at 23:34
  • How big is the door? Is it solid core wood, reinforced steel, etc.? Swinging door or sliding? Seals? – Lee Sam Apr 17 '20 at 23:38
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You could always use the lumber you have and reduce the spacing to something like 5 3/4" (that's the actual spacing ratio for a 2x4@16"oc) to get an equivalent amount of control over the deflection.

I would not use anything less than a 2x4 at 16" on center, or it's equivalent. The main reason for this is because if someone were to lean on that wall they could crack the boards on either side. This would not only ruin their appearance but it could reduce their acoustic performance. Additionally, if a seismic event were to occur the weight of all that materials you have on there would begin to move with the earthquake. It would bend the wall out of plane causing cracks. 2x4s at 16" is the code recommendation to avoid these cracks.

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  • I originally posted this over on woodworking where @SaSSafraS1232 has pointed out: "Dimensional lumber's actual sizes are 1/2" smaller than the nominal sizes. A "2x4" is 1 1/2 x 3 1/2". This was originally due to milling losses." which implies that my 38x63mm would be labelled as 2x3. When you talk of 2x4 is that the actual measurement you can take on the lumber? – Sterl42 Apr 18 '20 at 7:45
  • No it's nominal so I took the deflection from a 1.5"x3.5" member then got the equivalent spacing for a 1.5"x2.5" – represton Apr 18 '20 at 13:58
  • Not sure if these are available where you are or what code equivalent would be where you live, but that's a standard cut of lumber for an interior wall in the US. If you can't find 2x4s you can also do 2x6 (1.5"x5.5") at 2 feet on center. – represton Apr 18 '20 at 14:08

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