John Sayers' Recording Studio Design Forum Archive

No pics to prove it, but those things have a 3-5mm gap

Maybe I'm just a little slow at "getting it": So those wood blocks are ONLY in contact with the inner leaf? They do not touch the outer leaf anywhere? If so, then why do they go up above the outer-leaf joists? I'm just not seeing how you are going to keep your two leaves decoupled here... Are you planning to soffit around each and every one of those joists somehow? If so, how and why? If not, then back to the other question: why do the blocks extend up into the space between the joists? What's the purpose of that? The existing roof joists are outer leaf, and therefore must remain outside of the inner leaf at all points, and it's not clear to me how you are going to accomplish that...

which I intend to gap with a low modulus caulk like this...

What is the durometer hardness of that stuff, when it is cured? I checked on their website but could not find a data sheet for that specific product. They do have the data for some of their other products, but nothing at all for that one. It would be good to find out. to make sure it will work OK, to keep the leaves decoupled.


- Stuart -

Soundman2020 wrote:The existing roof joists are outer leaf, and therefore must remain outside of the inner leaf at all points, and it's not clear to me how you are going to accomplish that...

In short...I'm not. It is the compromise I arrived at
As I see it I had 4 choices:
1: Hang a ceiling off the existing joists using resilient channel to decouple it. The concern here is I was concerned about the amount of weight this would add to the joists as I am also supporting the outer leaf on those as well - it would be equivalent to the weight of more than 3 normal ceilings.
2. Interleave new joists resting on the new internal walls between the existing joists (I don't have much headroom to work with) and hang a ceiling off those. Doing this I lose about 40+ mm of headroom.
3. Just a new thought....I suppose I could add joists - as in glue and bolt a 90 x 45 to the existing joist to add strength (reduce deflection etc) - AND use resilient channel...which might be a solution for scenario 1?
4. Do an inside out ceiling with only one leaf and cop the lower TL that will result. It's much lighter...It gives me a higher effective (acoustic) ceiling...plus it's cheaper.

What say you?

Soundman2020 wrote:What is the durometer hardness of that stuff, when it is cured?

Yeah..hard to come by some of this info. Here's the Fyrethane data...I can't see durometer ratings
http://www.tremco.com.au/fileshare/Data ... 0Sheet.pdf
Or there's this stuff from the same people...I think this is a little softer from looking at the 'movement capability'.
http://www.tremco.com.au/fileshare/Data ... 0Sheet.pdf

Scott

The mention of Caulking.

Not sure this is applicable [as I follow your build thread].

There was forem conversation I followed with Rod Gervais [Build it like the Pros].

He mentioned a caulk he recommends called 'Big Stretch'. I'll be looking into this for my upcoming build.

I don't think Big Stretch is available in Australia, but this seems to be a recommended alternative -

http://www.hbfuller.com.au/products/tra ... 56631.html

Available at Masters. I think it's a polyurethane product which I believe is good for this purpose. There was a thread on here where John stated the pros & cons to each type of sealant and poly was highly regarded.

Cheers guys,

The Big stretch is not available as far as I can see here in Oz! Also, according to Stuart (aka Soundman2020), the Fuller stuff has too high a durometer rating, meaning it is too rigid when it cures - which is fine in some application but not in this. Trying to find something that has a rating below 20 on the durometer scale AND that's available here. I've been using the Fuller stuff for all the seals where non-resilience is not an issue.

I am looking seriously at option 3 above which will mean a different tack. I'm hoping for 30-40dB of attenuation, and I'm concerned the compromise will make that impossible.

Update 3/5/15
Further consideration has me thinking I will sister a 90 x 45mm pine beam to most (8 or 9 out of 12) of the existing joist in order to increase the load bearing capacity of that system. I will run the beam from outside leaf to outside leaf and ensure it is positioned down against those outer frames.

On top of the joist I will still use the 19mm particle board (yellow tongue flooring I mentioned earlier) as my outer leaf. I will use resilient clips to hang furring channel to hang the ceiling from as the inner leaf.

Considering the 16mm version this stuff for plaster board: Just going to go 1 layer at present ($$)
http://www.knaufplasterboard.com.au/upl ... P_2014.pdf

Really appreciate the look in guys. Any thoughts on my sistering idea?

Scott

My ventilation silencer box design. Using 18mm plywood and 50mm duct liner. Overall length should be 940mm and not the indicated 913...not sure what happened to the diagram there?? * I'll make two of these and they will sit right on the outer leaf - one for intake one for outlet - as indicated in an earlier drawing.
* I plan on using 200mm flexible ducting and an inline fan that I'll located in the ceiling space above the adjacent workshop.

I'm about to build silencers myslef, Do you know if there is much difference in the absobsion using duct liner compared to to material covered rockwool?

HI "Tombot". Please read the forum rules for posting (click here). You seem to be missing a couple of things!

Do you know if there is much difference in the absorption using duct liner compared to to material covered rockwool?

The difference in absorption isn't the issue: it's the difference in ablation, as the air flow removes fibers from the mineral wool, then sprays them all round the room... Doesn't happen with proper duct liner, which is specifically designed for the job.

- Stuart -

Silencer number one in progress... Design question...
I am planning on doing a whole wall bass trap for the rear (west) wall. I was going to do an inside-out wall AND this, but I'm thinking as this will give me a greater air gap it will be a better overall approach...yes?

Also, will this negate the need for superchunks in the rear corners or is it too early to say? Obviusly the door makes it difficult to do a superchunk there.

Scott

Progress pics... Any thoughts on my rear wall design??

Progress pics...
Insulating the south wall. Fluffy stuff in the cavity - higher density in the frame. West wall frame installed...finally Interleaving joists begins... Fixing and sealing the top (outer leaf) layer begins - which sits on top of the existing ceiling joists. Gotta sort out some of the ventilation side of things before all the internal joists go in. I have to assemble one of my silencers in the roof cavity...it's too big to get into the space in one piece...that should be fun! I have a plan.

Any comment on my rear wall bass trap design? Things I'm missing? ...tap tap..is this thing on?

Give me a shout out if you're following the thread

Interleaving joists begins...

Hard to tell from the photo ... but are you certain that the inner ceiling joist is NOT touching any of the outer shell ??

RJHollins wrote:

Interleaving joists begins...

Hard to tell from the photo ... but are you certain that the inner ceiling joist is NOT touching any of the outer shell ??

Yep - I've gone to great lengths on that front. There's a minimum 5mm gap.

Thanks for the look in.

hopefully the structure does not expand/contract due to temperature and settling, as that is less than a 1/4 inch clearance.

Progress pics...
Top layer going in. Got some duct liner...and some glue...and well...