Exterior Drum Practice room build plan, Wales, UK

Quick question: I'm wondering about filling some voids in the roof with expanding polyurethane foam. Can this stuff legitimately considered to be mass, or is it more akin to air?

Quick question: I'm wondering about filling some voids in the roof with expanding polyurethane foam. Can this stuff legitimately considered to be mass, or is it more akin to air?

Neither! :) It has very little mass, and it is also closed-cell foam (meaning air cannot get through), so it's not much use at all, acoustically. It's good thermally, and also for sealing gaps where water might get in, but not much going for it, acoustically. What "voids" are you planning to fill with it? - Stuart -

Soundman2020 wrote:

What "voids" are you planning to fill with it? - Stuart -

The void is essentially a gap above the top of the stud wall where the frame meets the outer skin and the roof (OSB). Hopefully you can see from the photo - I put some sections of 2x4 in between the joists for added support, but used scraps rather than measuring the exact length. With hindsight, I perhaps should have placed timber of the correct size there. Anyway, I will get my caulk gun in there and seal up where the board joints are, and thought I'd finish up with filling with foam. This is where I've got to - I still have some sections of OSB to put on the outside tomorrow, then I'll be going crazy with the caulk before the Tyvek goes on; followed by cedar cladding. The plan is to focus on getting the exterior properly watertight and airtight over the next few weeks before I start on the inner frame; and before Autumn in mid-Wales is upon me.. I have been caulking the studs on the inside where they join the OSB - but not the noggins. is this overdoing it? I was focussing on the studs where the join ran along the centre of the stud, so thought it may be helpful - but may be overkill? Another question! - With the inner frame, my plans are still evolving. I wondered if there would be any value in mounting the inner frame timber on anything (like strips of rubber) in an attempt to decouple them from the concrete pad (which the outer frame also sits on?). When I get to doing the floor, I will (hopefully - depending on picking one up at the right price) be laying an engineered wood floor on top of standard grade underlay - so it wont be floating to any decent level. Will attempting to isolate the inner frame as above make any real difference to the overall performance?

Really struggling to find a product suitable for lining my baffle boxes in the UK - aside from one product which will set me back over £200 for a roll (I need less than half a roll). I'm wondering if using rockwool slab covered with 2 layers of tight weave fabric would be appropriate? Not ideal obviously, but an option?

I'm wondering if using rockwool slab covered with 2 layers of tight weave fabric would be appropriate?

To be honest, I really would not go that route. It might work, it might not. You'd be pretty much on your own in figuring out the acoustic properties, and how it will stand up to air ablation over time, and if it will be grow fungus inside or not... Maybe you could contact a local HVAC supplier, and ask for their offcuts each week? It might take a while to get enough offcuts together of the right size, but it would be a lot cheaper than buying the roll! Just an idea... - Stuart -

Thanks Stuart - the mention of possible fungus has put an end to that idea! Will keep working on this

Hi folks Is there a document that compares STC for glass in various configurations? I'm currently weighing up 10mm toughened glass versus 10.8mm laminated glass. Will the PVA interlayer help or hinder in a M-A-M room design? I know that in some laminated glass the interlayer acts as a spring with the glass being a M-A-M system in its own right, so using two of these (one in each wall) would result in a 4 leaf design. Incidentally I finally found some pyrosorb to line my baffle boxes with... Cheers

I'm currently weighing up 10mm toughened glass versus 10.8mm laminated glass.

Take the laminated, for sure. To start with, it is nearly 10% thicker, plus it is laminated!

Will the PVA interlayer help or hinder in a M-A-M room design?

It won't do much for MAM (although it might help slighlty), but it does wonders for the coincidence dip.

I know that in some laminated glass the interlayer acts as a spring with the glass being a M-A-M system in its own right, so using two of these (one in each wall) would result in a 4 leaf design.

It's not a spring: it is a damper! It acts something like Green Glue in that sense. If you get proper acoustic PVB interlayer, then it's better still, but even normal PVB interlayer is still good. - Stuart -

Hi folks I thought I'd post my proposed wiring diagram - comments appreciated! Also, here's where I'm at with build progress. I'm going against convention with some aspects of the build 'evolving' - this has been more to do with cost and the fact that I've not been able to set out exactly whats going to be used where; I'm sourcing materials as I go along and getting the best / cheapest I can, for example reclaimed flooring. I have some temporary glass in. The amazing deal I got on used laminate glass went wrong when I dropped a pane. :oops: I've got a pane in that is quite scratched at the moment, which will be replaced by a new pane in due course. I have 10.8mm laminate in inner and outer frames.

my proposed wiring diagram - comments appreciated!

You seem to be chopping holes in your isolation walls all over the place! :shock: :ahh: That's a BIG non-no! ALL of your wiring must be done inside the room. You are allowed one single penetration to get the main power feed in, the from there you split it up and send it around the room using surface-mount channels, switches, outlets, light fittings, etc. Like this: http://www.calcentron.com/Pages/fram-tr ... aceway.htm http://www.export.legrand.com/EN/dlp-wa ... ng_95.html Sometimes called "trunking" or "raceway" systems. You also are showing straight-through ducts for your ventilation: :shock: :ahh: That's another big non-no! You need to have silencer boxes (a.k.a. "baffle boxes") on your ventilation ducts, and they need to be sized correctly to do the job. A ventilation duct is a huge hole in your wall, and totally negates all of your isolation. The ONLY way to get your isolation back again is to build silencer boxes that allow the air to get through, but stop the sound from getting through. Also, you show a switch for your fan, but you should probably get a variable speed controller (and a variable speed fan!) so you can easily adjust the flow rate, as needed.

The amazing deal I got on used laminate glass went wrong when I dropped a pane.

Ouch! I guess you could say that deal "fell through"... it even "shattered" previous records for such a deal... (And I probably should not be looking for a job as a comedian... :) ) - Stuart -

You seem to be chopping holes in your isolation walls all over the place! :shock: :ahh: That's a BIG non-no!

Fear not! I think thats more down to my dodgy diagram than anything else. The only penetration will be where the main feed comes in to the room. The only possible exception to this will be the maglock push buttons - unless I can find a way of wiring them to avoid this. If I do need to make a small penetration it will certainly be a big deal and I'll be sealing / overlapping and doing all I can to replace the integrity of the wall.

You also are showing straight-through ducts for your ventilation: :shock: :ahh: That's another big non-no! You need to have silencer boxes (a.k.a. "baffle boxes") on your ventilation ducts, and they need to be sized correctly to do the job.

As above, this is me being unclear with my diagram for the electrician (just wanted to illustrate for him what is where). :oops: There will a baffle box on the inside, leading to a flexible hose that is walled off behind a false wall. This attaches to a straight piece of plastic ducting through the inner frame, with an insulated flexible bit attached between the inner and outer frames. The supply then goes to the other straight ducting going through the outer frame. When it comes out of the outer frame it enters a sealed space on the outside of the building (a sealed cavity the same thickness as the wall) before winding through another baffle box. I'll write up my ventilation plan and post over the weekend to check this is appropriate... Sorry for the confusion

Aaah! That sounds better... :thu:

Hi all Quick question about my window glass. My glass may be up to 10mm smaller than the frame it's going in, which will leave a gap around the edges. I'm wondering how best to fill that space, which will be underneath / behind an inner frame trim. Will my acoustic caulk work as mass in that space? - or is there something else that I could fill the space with that would have a similar mass as my 10.8mm laminate glass? The 1x2 trim all around the inner frame will all be sealed up and air tight - it's more the issue of compromising the continuous mass that concerns me. Thoughts? Cheers

I would not try to fill such a large gap with caulk. I would suggest either rubber of some type (preferably Sorbothane, or maybe Neoprene), or just build out the frame with wood. Glass is about two to three times the density of wood, so an inch of wood will give you roughly the same surface density as 10mm of glass. Both of those rubbers are about half as dense as glass, so you'd need 3/4" thick (19mm) or so to keep the same surface density. So one plan could be to wrap 10mm Sorbothane sheeting around the edge of the glass, extending maybe 1/2" or so over the surface, then have 1/2" wood stops and trim to hold it all in place. That would do the trick, plus give you excellent seals all around the glass, and even excellent decoupling: your glass would float in the frame, fully isolatied. There's nothing better than Sorbohane for that. (Pricey, but excellent). - Stuart -

I would suggest either rubber of some type (preferably Sorbothane, or maybe Neoprene)

Great - some strips of 10mm x 3mm dense Neoprene ordered; thanks for the suggestion. I'm planning ahead to some future stages. My Auralex foam squares that have been in storage are looking really tired and faded in places, and I've been thinking about painting them. Logic - (and also google) - points to this being a bad idea as it would 'clog the pores' and reduce their efficacy. However, the link below counters that with some data. http://www.acousticsfirst.com/painted-acoustical-foam.htm So - I'm thinking I'll do this, at least with some of my foam.

... as long as you do it the correct way, like they did... :) - Stuart -

Hi all A couple of questions: For my inner frame ceiling, I'm running the joists through notches in the noggins in the outer frame joists (see pic below). I'm doing this simply to maximise room height; and reinforcing where the notches have been cut by mailing steel plates above each notch. The gap between inner frame joist and outer frame noggin will be around 5mm. Is this level of tolerance ok? I'm guessing that as long as there is no timber to timber contact this is ok? Secondly, I want to try and 'damp proof' my window by sealing the gap where the inner frame meets the outer frame. I wondered about glueing strips of tyvek face down so the waterproof side is facing away from the inside of the window. I dont want any humidity coming in through the gap. I'll then put a layer of calcium chloride crystals all along the base of the window frame, and the interior of the window frame will then be covered with a thin permeable neoprene that I have spare. I'm thinking that the relatively minor joining together of the frame via tyvek would not cause sound transmission from the inner to the outer frame (sound transmission through paper and neoprene would be minimal?) Thoughts welcome - cheers!

For my inner frame ceiling, I'm running the joists through notches in the noggins in the outer frame joists (see pic below).

:shock: :?: :?: :?: RED FLAGS!!! WAVING!!!! Did you get that approved by a structural engineer? There's a reason why those cross-bracing members are in there.... Are you certain that it is safe, legal, and advisable to do that? Do you have a signed report from a qualified structural engineer that says you can do that?

Secondly, I want to try and 'damp proof' my window by sealing the gap where the inner frame meets the outer frame.

Why would you want to do that? Where do you think the "damp" is going to come from? Did you fail to seal the floor and walls properly before you started, and you are now concerned about humidity rising through the floor, or seeping through the walls? What is the source of the "damp" that you are concerned about? And how will you prevent it from rotting your studs, joists and walls in general, even if you do manage to seal the window? I'm not sure I follow your reasoning at all... If there is a damp problem, it must be fixed at the source, not the destination.

I dont want any humidity coming in through the gap

That's the big question here! Where is that humidity going to come from? What did you not seal that is causing you concern? It would be far, far better to go back and seal that now, rather than try to protect only your window: If you have a dam problem, you absolutely must fix that before you build any walls at all!

I'll then put a layer of calcium chloride crystals

Why calcium chloride? Why not use a desiccant that is chemically inert, mush easier to handle, works faster, is cheaper, and holds a lot more moisture? In other words, just use what everybody else does: plain old silica gel. Also, if you do want use calcium chloride, have you calculated how much you will need? There are equations that you need to use to make sure that you have the correct amount of desiccant inside the window cavity. Did you do that? And did you use the correct equation for calcium chloride?

I wondered about glueing strips of tyvek face down so the waterproof side is facing away from the inside of the window

That would not work. Tyvek is not a vapor barrier: it is a water barrier. It will not stop humidity from getting through. In fact, that is it's whole purpose! It blocks water, but allows the wall to breath, expelling water vapor through it to the outside world. So putting Tyvek around your window gap would actually do the opposite of what you are hoping it would do: it would allow any humidity in the wall cavity to migrate into the window cavity, where it will condense on the glass as soon as the adsorption capacity of your calcium chloride is fully used. It seems to me that you should go back to the beginning, and first solve your humidity problems. There should be no way at all that moisture can ever penetrate into your wall cavity. The very fact that you think this is going to be a big problem, shows that you didn't seal something the way it was supposed to be sealed. You need to go back to that point and seal it, then move forward again. Yes, you do need the correct amount of desiccant in your window cavity to adsorb the small amount of water vapor that will be trapped in there when you close it up, those preventing condensation in the interior surfaces of the glass. But that's not what you are talking about here: you seem to be talking about major humidity problems. Those should never happen in the first place if your outer-leaf is sealed correctly. - Stuart -

RED FLAGS!!! WAVING!!!! Did you get that approved by a structural engineer? There's a reason why those cross-bracing members are in there.... Are you certain that it is safe, legal, and advisable to do that? Do you have a signed report from a qualified structural engineer that says you can do that?

My build doesn't meet the scope for building control so I haven't had a structural engineer involved formally. I have had informal guidance from a structural engineer though. Given my roof structure is at the upper end of building regs guidelines I'm comfortable with this - particularly as the steel nail plates are deigned for more heavy duty work than this and they more than replace the noggin strength that I've reduced through cutting a notch.

Why would you want to do that? Where do you think the "damp" is going to come from? Yes, you do need the correct amount of desiccant in your window cavity to adsorb the small amount of water vapor that will be trapped in there when you close it up, those preventing condensation in the interior surfaces of the glass.But that's not what you are talking about here

Actually, that's precisely what I'm talking about. I want to seal the unit to avoid any condensation problems inside the window; from pre existing moisture there now, and also moisture that may build up over time from atmospheric water vapour / differences in internal and external temperature, etc. hence sealing the gap between the frames. Given that the frames shouldn't touch, what's a good way to do this?

I want to seal the unit to avoid any condensation problems inside the window; from pre existing moisture there now,

Right. That's what the silica gel will do. It will adsorb any humidity that is trapped in the cavity.

and also moisture that may build up over time from atmospheric water vapour

And once again the question: Where do you suspect that the additional humidity is going to come from? If the walls are properly built, and the shell is properly sealed, then there should be no path for additional humidity to get in.

from atmospheric water vapour / differences in internal and external temperature, etc.

What would drive the humidity into the wall cavity? That's the question. There would have to be a permanent difference in pressure between the wall cavity and the inside of the room, or the outside of the building, as well as substantial gaps, cracks, holes or crevices that would allow the humid air to move. If you walls are correctly built, that should not happen. Unless you provide a driving force and a path for air to move into and out of that cavity, there is no reason for it to do so. Ditto for humidity: unless there is a source of humidity inside the cavity, there is no reason why the humidity in the cavity would increase. Once the silica gel has done its job of adsorbing the water vapor trapped in the cavity between the windows, that's the end of the story. Assuming, of course, that there is no source of additional moisture, and no driving force that would cause air movement.

Given that the frames shouldn't touch, what's a good way to do this?

Once again, if you build the place correctly, there is no need to do that. The NORMAL way of dealing with that gap is to wrap a piece of OC-703 in black fabric and place that across the gap around the sides and top, and to also include silica gel under the fabric in some way across the bottom. - Stuart -

The NORMAL way of dealing with that gap is to wrap a piece of OC-703 in black fabric and place that across the gap around the sides and top, and to also include silica gel under the fabric in some way across the bottom.

Thanks Stuart - thats what I'll do. Getting OC-703 is tricky in the UK but I believe that Rockwool do a product thats similar. The other bit I'm still not quite sure of is the gap between the door frames, which will be the only area where air and moisture could get in. I was planning to close the gap between the two door frames with some strips of 3x1 timber to effectively make the gap much smaller (around 5mm) and then fill the 5mm gap with acoustic sealant- so the inner and outer frames are effectively sealed up but the join is via acoustic caulk. Is this the correct way to do it? I'll post some photos of this stage if the above hasn't made sense

Getting OC-703 is tricky in the UK but I believe that Rockwool do a product thats similar.

That would work fine. Anything that is semi-rigid and not too dense would be good.

The other bit I'm still not quite sure of is the gap between the door frames,

Same thing! Semi-rigid slab of insulation wrapped in fabric, and press-fitted into the gap.

I was planning to close the gap between the two door frames with some strips of 3x1 timber to effectively make the gap much smaller (around 5mm) and then fill the 5mm gap with acoustic sealant

You could do that too, but set it backwards a bit into the cavity, skip the sealant, and put your fabric-wrapped insulation in front of it, with some wood trim on each side to make it look prettier.

so the inner and outer frames are effectively sealed up but the join is via acoustic caulk.

Unless you can find some "high elasticity" caulk, with a Shore 00 durometer rating of about 60 or less, then I'd skip that. Ordinary caulk is flexible, yes, but it can still create flanking paths for low frequency vibration, which might or might not be an issue, depending on how much isolation you are shooting for. Oh, and Happy New Year!!! - Stuart -

Thanks as always for the excellent advice you've given over the past year Stuart - the time and effort you put into advising and guiding others is hugely appreciated. Hope you have a fantastic year.

Hi I need to bridge the gap somehow between the bottom of my door frames - picture below. I thought that cutting some timber to fit snugly between the two frames, resting on the 2x4 frame footers for each frame? To deal with the flanking issue, I have some 5mm hard neoprene strips, which I could put underneath this piece of timber - and also on both long sides of the timber where it makes contact with each door frame. This will effectively create a floating timber step in between the door frames, which will be flush with the bottom of the door frames. Is this the right way to do this? The sides and top of the door frames will have rockwool slab cut to size, wrapped in fabric and stuffed in the gap as previously discussed. Cheers

To deal with the flanking issue, I have some 5mm hard neoprene strips, which I could put underneath this piece of timber - and also on both long sides of the timber where it makes contact with each door frame. This will effectively create a floating timber step in between the door frames, which will be flush with the bottom of the door frames.

The concept is fine, but I wouldn't use hard neoprene for that. How hard is it? What is the durometer, Shore A? If you don't know, or if it is too high (anything above about 30 or so), then skip that and get some Sorbothane instead. That's the best stuff there is. Put strips of that under the wood insert, leave a gap of a couple of mm between the wood and the door frame on each side, and caulk that with some high-elasticity caulk (not normal caulk), to seal the gap. - Stuart -