Drywall Screwing Schedual

[hally]

Hi,
Quick question about screwing schedule, I'm using a a more dense 15mm drywall board than the standard board, its made by gyproc and its called Duraline. Its density is 927 kg/m3.... Do i use the same screwing schedule, Edges: 8 inches apart, Field: 16 inches apart. my studs are @ 24" centers. Also is it safe to do a half schedule on the 1st layer and then a full schedule on the 2nd final layer?
thanks for any advise
hally

[Soundman2020]

Do i use the same screwing schedule, Edges: 8 inches apart, Field: 16 inches apart. my studs are @ 24" centers.

I would expect that the same schedule is applicable, but don't take my word for it! Ask the manufacturer.

Also is it safe to do a half schedule on the 1st layer and then a full schedule on the 2nd final layer?

That should be fine, as it implies that the first layer will have 50% more than is needed, and the second layer will have the right amount, so I don't see a problem there. Just remember that the screws for the second layer need to be 15mm LONGER than the ones you use on the first layer, to ensure the correct penetration depth into the studs. But check with your local building code and/or inspector, to make sure that is approved practice where you live.

- Stuart -

[hally]

Thanks a mill Stuart

[hally]

Do i use the same screwing schedule, Edges: 8 inches apart, Field: 16 inches apart. my studs are @ 24" centers.

I would expect that the same schedule is applicable, but don't take my word for it! Ask the manufacturer.

Also is it safe to do a half schedule on the 1st layer and then a full schedule on the 2nd final layer?

That should be fine, as it implies that the first layer will have 50% more than is needed, and the second layer will have the right amount, so I don't see a problem there. Just remember that the screws for the second layer need to be 15mm LONGER than the ones you use on the first layer, to ensure the correct penetration depth into the studs. But check with your local building code and/or inspector, to make sure that is approved practice where you live.

- Stuart -

Quick question Stuart while we are chatting, for inside out walls what is the minimum airspace that is acceptable between inner and outer leaf. my outer leaf is 4" solid concrete block with plaster to seal it airtight and my inner leaf walls will be timber stud partition with 2 layers of 15mm Soundbloc plasterboard (1600 kg/3m). I want to build the inner leaf inside out... can i reduce the airspace to 50mm (2") filled with pink insulation given the density of the concrete blocks?

regards
hally

[Gregwor]

Here is a TL calculator I scabbed together in Excel:

TL Calculator

Type in your densities and spring gap and it will tell you how it will perform. Adjust your gap amount to see how much improvement or diminishment is made. Make your decision from that!

Greg

[hally]

Thanks Greg, the XL sheet is'nt working for me, my outter and inner leafs are different densities and the xl doc won't let me adjust the 2nd leaf. Any idea how to make it work. My 2nd leaf is 4" solid concrete block with a thin render, approx 32 kg/m^2 surface density, my inner leaf is 2 layers of firecore drywall @ 26 kg/m^2.
thanks
hally

[Soundman2020]

4" solid concrete block with a thin render, approx 32 kg/m^2 surface density,

That's not correct. Density of concrete is around 2400 kg/m3. 4" is 10.16cm = 0.1016m. Thus, the surface density of a 4" thick concrete wall is 243.84 kg/m2. Not sure where you got your figure from, but it is way, way off.


- Stuart -

[hally]

4" solid concrete block with a thin render, approx 32 kg/m^2 surface density,

That's not correct. Density of concrete is around 2400 kg/m3. 4" is 10.16cm = 0.1016m. Thus, the surface density of a 4" thick concrete wall is 243.84 kg/m2. Not sure where you got your figure from, but it is way, way off.


- Stuart -

Yes I was way off, not sure what happened to my calculations, thanks Stuart

Any suggestions on what my minimum air gap filled with insulation could be?
Thanks
hally

[Gregwor]

Any idea how to make it work.

Halley TL.png

I left the drywall at 10.7 kg/m^2 instead of 13 as per your guesstimate because there are a lot of variances in building supplies. I'd personally calculate it using this lower surface density because you never know what your batch of drywall will be.

How I made it work: the comments on the right hand side indicated that the cell was just getting the 2nd leaf density by multiplying the weight of one layer of drywall by 2. It's just an =B2*2 equation, so I just erased that and put in your concrete density.

For the gap (space) I've changed the comments for you so you have a better idea of what values to change.

Any suggestions on what my minimum air gap filled with insulation could be?

As I implied earlier, maybe your isolation requirements only need you to have an 1/8" gap. Or maybe a 4ft gap. Use the calculator to see how much the gap size (or more drywall) changes the wall's performance and that's your answer.

Greg

[Soundman2020]

Any suggestions on what my minimum air gap filled with insulation could be?

As Greg mentioned, that depends on what your isolation needs are. How much isolation do you need (in decibels), and what's the lowest frequency that you need it for? Those are two key questions.

Personally, I would not go much below 4" (10cm) for the air gap, regardless of wall construction or material densities, as the other resonances inside the wall can start t be significant with small gaps.

- Stuart -