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Garden timber studio - walls

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Garden timber studio - walls

Postby jmch » Mon Oct 22, 2018 5:09 pm

Hi

I've asked a builder to build a garden studio for me. Due to budget, it will be timber-built, sitting on a new concrete slab with brick/block footings to damp level only.

I've read Rod Gervais's book and lots of helpful posts here and elsewhere, and grasp the 'room within a room' / decoupling concept.

My nearest neighbour's house is 15 metres away and it's a very quiet garden/neighbourhood. But I want to be able to track live drums at some point.

Make up of my walls from outside to in:

Red wood cladding on top of damp proof membrane fixed directly onto
22mm OSB board fixed to
Timber framing
Between the batons: Rockwool RW3 100mm insulation (density 60 kg/m3)
Small air gap (circa 100mm)
More Rockwool RW3 100mm insulation
Timber frame
Double thickness fire board (with green glue between) fixed directly to frame

Ceiling from the outside roof:

Shingle tiles on top of damp proof membrane fixed directly onto
22mm OSB board fixed to
Timber framing
Between the batons: Rockwool RW3 100mm insulation (density 60 kg/m3)
Small air gap (circa 100mm)
More Rockwool RW3 100mm insulation
Timber frame
Double thickness fire board (with green glue between) fixed directly to frame

I read that RW3 was the best insulation to use to provide sound proofing but I understand this is only really effective at mid to high frequencies.

I spoke with Rockwool and they said :

"To be honest, using the different density products does not really affect the overall dB reduction, please see attached Wall '02' using ROCKWOOL Flexi at 35kg/m3 instead of the RW3 which performs in the same way.

Also, filling the space between the studs with ROCKWOOL Flexi (Wall 03) does not improve the construction any further - any further improvements will only be achievable using more layers of plasterboard and the resilient bars."

So I get I need as much mass as possible.

I have 3 particular questions I'd really appreciate some views on:

1. Do I have enough mass in my outline above - both inner and outer leafs?

2. Should I go with RW3 in between the timber batons or downgrade to their Flexi insulation?

3.Should the gap between the two decoupled leafs be empty or should I also add some softer, 'fluffy' insulation in this gap?

I appreciate it's not an ideal build to achieve massive dB reduction, but I am hopeful it will be around 50dB, which will be sufficient for my situation, I feel.

Thanks
John
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Re: Garden timber studio - walls

Postby blinddrew » Mon Oct 22, 2018 5:41 pm

Hi John,
Having just finished Rod's book as well it certainly seems like you're in the right direction. You could add another layer of board outside and in to increase the mass but I'd leave the air gap as a proper gap. Given those walls, the challenge will be to make sure your builder actually follows the design properly and doesn't leave anything 'good enough' to scupper it.
What's your plan for doors / windows / ventillation?
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Re: Garden timber studio - walls

Postby jmch » Mon Oct 22, 2018 9:02 pm

Hi Blinddrew
Thanks for the encouragement mate. I hope I am going at it in the right way. And yes I'm on my builder's case the whole time - it's certainly not cheap.
I was indeed thinking of adding another layer of board to the outside, before the redwood cladding goes on. I guess I can wait til the end and do some levels testing.
I can't afford aircon right now but will be adding in a fresh air intake and exhaust fan, which will duct in through the void in the roof and feed through into silencer/baffle boxes. I'll also use an electric radiator when needed.
Door wise, I'll be having two solid fire doors which will be decoupled. Not going to bother with a window - again my budget can't stretch.
I really need some opinions on the three specific questions I posted. Those are the things I just can't get straight in my head. Thank you for your suggestion re the air gap. I've read both sides of the argument - leave it empty and fill it with soft insulation. My builder has suggested soft insulation bats for it.
Any thoughts on my other two questions?
And what are you planning/doing?
Cheers
John
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Re: Garden timber studio - walls

Postby blinddrew » Mon Oct 22, 2018 10:55 pm

I think maybe the outside is a bit light. Another caulked layer of board would probably be useful. To be frank, you can rarely go wrong with more mass but two layers plus green glue outperforms four layers without (iirc) so that should be ok.
As to the different kinds of rockwool, might be worth trying an email to mr G directly?
I'd be surprised if there was a great deal of difference between similarish densities.

I'm still at the research stage at the moment, too many things up in the air to do more than read up on it.
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Re: Garden timber studio - walls

Postby James Perrett » Tue Oct 23, 2018 12:41 am

You're not going to get anything like the soundproofing you need from that structure. The outer layer has to be far heavier than OSB with cladding. My first studio had a similar outer structure - it was little better than playing in the open air.

At a bare minimum you'll need to use standard concrete blocks in the outer walls but medium density blocks are better still.
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Re: Garden timber studio - walls

Postby jmch » Tue Oct 23, 2018 5:38 am

Thanks for the feedback.

James I'm surprised to hear you say concrete is my only option. I've recorded in bands in more than one garden timber shed and the sound reduction was sufficient.

However, that was before I turned my thoughts towards doing it myself. So I completely accept that my plan might be less than perfect and I don't have enough mass.

Given my budget constraints, it has to be timber. I'd appreciate your view on what I could do to help matters in this context. Another layer of 22mm OSB on the outer walls and roof? Or add a layer of fire board to these leafs? Obviously the increased roof load would have to be bearable.

Thanks
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Re: Garden timber studio - walls

Postby blinddrew » Tue Oct 23, 2018 9:54 am

I'm a bit surprised by that as well James. Obviously you have the hands on experience but a wall as jmch describes (assuming a second layer of drywall on the outside) is pretty much exactly as RG outlines in his book as being good for 63dB of isolation.
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Re: Garden timber studio - walls

Postby Sam Spoons » Tue Oct 23, 2018 10:51 am

'Music' is far more intrusive than other more random forms of noise when unwanted. The neighbours will likely be much more sensitive to a low level of drums in the background than, say vehicle engines or such like.
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Re: Garden timber studio - walls

Postby kinglouis » Tue Oct 23, 2018 12:00 pm

Hi,

Sounds like a great project.

I've built three garden studios in different contexts, I can't claim to be an expert but can happily share my experience briefly.

1. Feather edge shed to start with over an OSB raised floor. Never going to hold in much sound but we constructed an OSB and 2"x4" frames filled with 4" rock wool to make an internal subframe, separated from the original structure by 2", with a 4" rock wool false ceiling, covered it all in calico or some such. As expected it didn't really stop any sound escaping but the acoustics made it a reasonable place to monitor and mix, and noise from outside was reduced a reasonable amount.

2. A SIPs panel frame (12mm OSB clad over 4" kingspan on both sides) on a concrete pad with 6" insulation in the roof, externally clad in 2" scaffold planks, plaster board on the inside. Not intended as a recording space but that's how it ended up. A thick wall for sure and good heat insulation but nowhere near enough mass to make a significant impact on sound.

3. Thermalite block shed. We built an internal stud wall with 4" rock wool slabs and put 4" in the ceiling plus two HEAVY sets of doors with very good seals. On the inside of the stud wall we plasterboarded and put green acoustic glue to seal all gaps between plasterboard and where it met the ceiling (which was a possible waste of time given the ceiling was only rafters with rock wool in between, but we did it anyway.) Then clad the internal plasterboard walls with wood. Diagonal t&g. Very 70s.

This was by far the most sound-proof room, and we were very surprised at its acoustic properties. Sounded great internally and you could only faintly hear a live kit being played if you stood outside. What I took from it was that whilst you definitely need rock wool and two walls with an air gap, nothing beats mass mass mass, even the thermalites were enough to make a significant impact. OSB isn't really helpful, plasterboard is better, even a few layers if you can. My long-term studio will be concrete block outside, gap, then stud wall with 4" rock wool, plasterboard, wood cladding. I know this isn't in your budget but I hope the examples are in some way helpful.

Hope that's useful, its only my experience but good luck with the project.
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Re: Garden timber studio - walls

Postby blinddrew » Tue Oct 23, 2018 1:12 pm

Ah, sorry, my bad, I have misunderstood the original post and have been thinking plaster-board instead of OSB. That is going to need more mass. Sorry. :(
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Re: Garden timber studio - walls

Postby James Perrett » Tue Oct 23, 2018 2:41 pm

jmch wrote:Given my budget constraints, it has to be timber. I'd appreciate your view on what I could do to help matters in this context.

Have you actually asked your builder how much it would cost to build it out of blocks? Given that you already have the base and a layer of bricks it may well be less than you think. There's really no way around it if you want to keep the neighbourhood quiet.

All of the timber constructed studios that I've seen have relied on having very forgiving neighbours - most of the owners thought that the soundproofing was great but it was always obvious to me when a band was playing inside.
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Re: Garden timber studio - walls

Postby jmch » Wed Oct 24, 2018 8:38 am

Thanks for the feedback guys. Kinglouis, your projects all sound interesting and you must have learned a lot. James, thank you for taking the time but I'm disapppointed by your 'this is the only way - there's no alternative' approach instead of offering me some help on the project I'm bound to for various reasons. You've clearly got a lot of experience and I fully appreciate I've not got the ideal set up but I've had a few people adopt a purist attitude when that just doesn't help me.

What does anyone think of these boards? I could put them on the outside of the exterior OSB, they have a density similar to acoustic board. Could they be green glued to the OSB board? Then my wooden cladding on the outside. Surely that would give me a lot more mass?

https://www.siniat.co.uk/en/products-an ... er-defence

Thanks again.
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Re: Garden timber studio - walls

Postby kinglouis » Wed Oct 24, 2018 9:58 am

Those boards look interesting - but they're quite dear too. Might be worth comparing mass of one skin of them Vs 2 layers of 12mm plasterboard. A single sheet of plasterboard is a fifth of the price of a Siniat sheet so you could do two skins of plasterboard, both layers green glued and airtight.

If the Siniat boards are heavy as buggery then maybe they're worth a shot!
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Re: Garden timber studio - walls

Postby Sam Spoons » Wed Oct 24, 2018 10:04 am

Slightly off topic but what is it that makes 'Green Glue' so effective?
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Re: Garden timber studio - walls

Postby kinglouis » Wed Oct 24, 2018 10:07 am

If I remember rightly it retains a bit more viscosity than other silicon, making it a bit less likely to crack. I'm sure there are other features too...
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Re: Garden timber studio - walls

Postby jmch » Wed Oct 24, 2018 10:52 am

Cheers kinglouis. Because the foundations are dug and the first concrete pour has been done, I'm being told by my builder that any additional mass on the walls has to go outside the OSB board he's ordered. So interior drywall boards are not an option as they're too close to the outside (it'd just be redwood cladding with membrane over them). So I was thinking I could use these siniat boards between the OSB and the cladding as they're designed to be weather proof as well as heavy. But yes the cost might be too much.
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Re: Garden timber studio - walls

Postby kinglouis » Wed Oct 24, 2018 10:58 am

If that's what you've been told then they found like a good option.
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Re: Garden timber studio - walls

Postby blinddrew » Wed Oct 24, 2018 2:54 pm

kinglouis wrote:If I remember rightly it retains a bit more viscosity than other silicon, making it a bit less likely to crack. I'm sure there are other features too...
In remaining elastic it also acts as an energy absorber. As the panels flex with vibration the green glue stretches and compresses and transforms that mechanical energy to heat.
If you use a glue that sets solid it can't perform that additional function.
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Re: Garden timber studio - walls

Postby jmch » Wed Oct 24, 2018 3:25 pm

Thanks blinddrew. I understand the properties of green glue and I am using it for my double layer of sound board on my internal walls. But I just wasn't sure if you could use it to adhere this weather defender board to standard OSB board.
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Re: Garden timber studio - walls

Postby blinddrew » Wed Oct 24, 2018 3:36 pm

Sorry jmch, it's not something I've got hands on experience with, I was just responding to Sam's query.
What's the density of the board?
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