Load strength of timber stud walls

[catnipsta]

Hi

I live in a GF flat, and would like to install independent ceilings with sound insulation to my 2 bedrooms (both are 3m x 3m in size).

The bedrooms are separated by a timber stud wall (47x100mm studs with 600mm centres), and solid outer walls on the opposite sides.

The plan is to fix 50x150mm C16 joist timbers (400mm spacing) using a bearer to the stud wall and hangers on the solid wall ends. The joists will be supporting acoustic mineral wool slabs (AMW 60 100mm 60kg/m3 density) and 2 layers of 12.5 acoustic plasterboard.

My concern is whether the stud wall is strong enough to support the new independent ceiling weight.

Many thanks in advance.

 

[big-all]

most off the annoying noise will travel through the structure

you only need a light structure as the total loading 54kg spread over 9 square metres plus plasterboard probably 4x2" would be enough

and choose your spacings to suit the plasterboard size

 

[Blagard]

catnipsta

I really don't think your partition wall will have any problems with that loading what so ever especially as it is spread evenly.

New ceiling joists (per Building Regs) for that span would be as big-all has suggested. -You are going to load up the ceiling with a bit more than the usual plasterboard and insulation. Bearing in mind we all stick things in our lofts without any real problems, again I think you should still be OK with the smaller joists.

Would love to hear what difference it makes no pun intended!

 

[catnipsta]

Thanks Big-all & Blagard for your advice.

With regards to the ceiling joist size, it was recommended by (soundstop.co.uk) that the joist needed to support 23kg/m2.

Looking at one of the KD C16 softwood Span Tables, and taking into account the span width of the rooms (3m), I figured that I needed 50x150mm joists with maximum 450mm spacings.

As long as the stud wall is sufficiently strong enough to bear the 150mm joists, I will be happy. My local timber merchant is charging £1.80 +VAT for the 150mm, and the 100mm is 20p cheaper.

 

[Blagard]

Thanks Big-all & Blagard for your advice.
With regards to the ceiling joist size, it was recommended by (soundstop.co.uk) that the joist needed to support 23kg/m2.

Looking at one of the KD C16 softwood Span Tables, and taking into account the span width of the rooms (3m), I figured that I needed 50x150mm joists with maximum 450mm spacings.

I see where you have come from. Soundstop must have a fairly comfortable margin of safety in those figues by my reckoning! All the same you are best to start from there if your system follows the same specification.

Regards the Table - That is for floor joist dead loads. In addition to those loads are some hefty allowances for imposed loads! I found this that may help you understand
http://www.home-extension.co.uk/tech2.html
Its your money / choice at the end.
PS as a rough guide timber is sold by the M3 so a 20p saving is not very good. I would have expect closer to 50p making the 100X50 £1.30+VAT/m

I was paying 1.10+Vat in October for SC16 97x47 for a DIY Job. Only 24m bought! Builders I would expect get it cheaper still. Excuse my edit on figures I apparently can't add now or spell!

 

[Chukka63]

have you considered underboarding the ceiling with insulated plasterboard??.i dont know anything about accoustics,just an idea.

 

[Blagard]

have you considered underboarding the ceiling with insulated plasterboard??.i dont know anything about accoustics,just an idea.

Chukka
I reckon he knows more about accoustics than the pair of us. check out those sites in his posting! "The proof of the pudding ..." as the saying goes. I know mass is one the best sound insulators and there is certainly plenty of that going in and more wall for it to travel in before it emerges. The weakest spot I can see is the partition wall itself.

For what it is worth Travel Inns I have been involved with have had two layers of 19mm wall boards each side of a stud with a mineral wool infill the stud may also have been split to further reduce structure bourne sound. Can't recall the floor/ceiling detail tho! Sound performance on those builds were good. - Can't speak for other projects though as quality control is important to eliminate airbourne sounds due poor workmanship.

My last contract had two "test cells" separated with two 250mm concrete walls with a 50mm cavity (550mm overall)! Isolated plinths coming from the basement below, that was a 6m column with the test item on top! Floors a mere 500mm thick solid concrete.

 

[Deluks]

The 50mm of headroom lost with the 150mm timber will gain you an extra 50mm or so of soundproofing. Airgap between partitions is an important factor in reducing sound transmission, and as Tesco say, every little helps!
For maximum benefit the cavity should be completely filled with rockwool (or equiv) although 100mm should be considered a bare minimum. You then may get away with a single layer of 9.5mm over a standard 12.5, or just use a single layer of the 19mm gyproc plank.

Also consider that you can put less PB on the timbers of you affix a sheet directly to the ceiling above before fixing the new joists.

With all this in mind I'd personally be going for:
12.5mm standard pb on the ceiling, fill all joins/perimeter with acoustic sealant.
Add 100mm joists @ 400mm centres, spaced 12mm from the PB you just fixed up. (steel herringbone strutting down the middle)

Fill void with 100mm rockwool slab.
Attach single layer of gyp-plank or 12+9 as previously mentioned. Definitely the latter if not skimming afterwards.

As L.T.M. mentioned, sound will still travel through the studs but you will reduce most of the airborne sound using these methods. Unless your upstairs neighbour is Fatboy Slim.



Ps. never mind soundstops products, get rockwool slabs from your timber merch and save a few quid.

 

[catnipsta]

I will be adding a layer of 12.5mm soundboard onto the existing ceiling with a gap around the perimeter to be filled with acoustic sealant.

I am also planning to leave a gap of 25mm between this new installed soundboard and the top of the new joists (as stated in Approved Document E 2003).

My main concern is in whether the 47x100mm stud wall is strong enough to support the ceiling loads of the 2 bedrooms. From my calculations each room requires 8 x 3m joists, the stud wall would need to support 2 sets of 6 joists and 1 bearer (50x150mm) - the 2 outer-most joists will be fixed onto the side walls. I am thinking that the these side joists can be cut so that they too can provide some support for the bearers themselves.

Are there any places where I can find a table that shows me how much load a stud wall such as mine can support?

BTW..my existing ceiling is 2.9m, which I assume would need to be factored in when calculating the load support of the stud wall?

 

[Deluks]

By soundboard do you mean sound reduction plasterboard, or the fibrous lightweight board sold as a soundproofing product?
If your joists are filled with 100mm rockwool then plasterboard would be better.

In any case, 100mm joists will be fine over 3m @ 400centres, and your stud wall will hold up just fine a well. And as mentioned, 2 layers of 12.5 may be more than necessary, so use slightly less or use a single layer thicker board.

Do you know what the existing construction is, going upwards?

 

[catnipsta]

Thanks Deluks

Yes, by soundboard I meant soundproof plasterboard (the blueish coloured ones)

Above my flat is just another residential apartment.

I'll place my order for the 100mm joists and the other materials this week,

Thanks everyone for all your advice.