Planning a garden drum studio

[nick_c]

Hello everybody,

Firstly - what an amazing place this is - I feel very lucky to have found it. I'm still reading through the saga of the basement studio in Athens where the poor guy had a rough time with contractors that didn't know what they were doing! I hope it worked out OK in the end...

I have a couple of fundamental questions to do with material selection for constructing a garden studio. Allow me to set out my objectives, then I'll ask the questions

I have a garden that is 5.5m wide and quite a good length. I'm just starting to plan the design of a garden studio that I can can use for drum practice on my acoustic kit - and maybe a bit of jamming with bass and guitar too (if there's enough room inside once we've added all the necessary isolation measures). It has to look good from the outside too - that the only way I could get the boss (wife) to agree to this, so whatever we end up building it out of, we'll probably clad it in red cedar or similar.

It going to go down the far end of the garden so its away from my house (and my neighbour's houses) - see this images below for the site plan and the plot on the ground.

plot-overview.gif

garden-studio-plot.jpg

Now, ideally I'm aiming to do this without getting planning permission from the local council - and I can do this under the 'permitted development' rules. However, because we'll be building within 2 meters of the boundary - the overall height of the studio must not exceed 2.5m. Also, I plan not to build the studio right at the end of the garden, but bring it forward from the rear boundary by a couple of meters - leaving room for me to store all the crap from the garden behind there out of sight. Of course, in order for me to access this, I will need to leave enough room down the side of the studio for me to get down there with a wheel barrow etc. My wheel barrow is about 80cm wide.

So, in terms of exterior dimensions, I think I've got approximately 4.7 meters of width to play with. Depth is not so much of an issue, but it will have to be something sensible between 3 and 4 meters.

I plan to build a room within a room.
I have a budget of around £5000 - £7000.
It needs some daylight in it.
It needs some ventilation in it.
I have some construction skills myself, but will be doing this with a friend of mine who is a carpenter (and also a musician) and we'll get in necessary tradesmen when we need to.

For the inner leaf I was planning 2 sheets of acoustic plasterboard (as we call it here in the UK) bonded together with Green Glue, mounted on resilient channel, mounted on 2x2 studwork.
I'm planning to do a concrete slab for the floor directly onto compacted hardcore. Depending on the construction of the outer wall, we may need to dig some footings too.

And so to my questions:

1. What is the best material to make the outer wall from? I was thinking that using dense breeze block (100mm thick liek this: http://www.wickes.co.uk/Wickes-Dense-Bl ... m/p/113505) may be a good thing to get some good mass into the wall. Is this going to be any better for soundproofing than using SIPS panels or even OSB on a timber frame?

2. How thick should I make my concrete slab?

3. What is going to be best for roof construction to maximise isolation? Its going to be a flat roof with a gentle slope to the rear - probably finished with EDPM rubber roof covering.

4. How large an air-gap should I leave between the 2 leaves? I could probably stretch to 20cm, but 10cm would be better for clawing back some of the inside space

5. How should I get the electricity cable into the building without compromising all the soundproofing work? I'll be running armoured cable up from the house - so would it be sensible to get that in before the concrete slab is poured and have it poking up from the slab ready to be connected up?

6. Am I in fantasy land that I can do this and achieve enough soundproofing that I could go and thrash about on the drums at midnight and no-one would hear a thing?

[Soundman2020]

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

the overall height of the studio must not exceed 2.5m.

But it can still be higher... if you dig down a bit. Your ROOF can't be higher than 2.5m, but that's above GRADE. You can sink the studio down a bit and still have a high ceiling.

I've got approximately 4.7 meters of width ... Depth ... will have to be ....between 3 and 4 meters. - I have a budget of around £5000 - £7000.

That doesn't add up too well. That's about 18 to 19 m2 of floor are that you are talking about, roughly. As far as I can see from designing studios for some of my paying customers in the UK (which seems to be where you live....), the going rate for building an external building like that is around £500 to £1000 per square meter. So you would need about £9,000 to £19,000 to do that. Call it 10k to 20k to be on the safe side. You'll need to revise your budget.

For the inner leaf I was planning 2 sheets of acoustic plasterboard (as we call it here in the UK) bonded together with Green Glue,

Green Glue does not bond anything to anything. It is not an adhesive. It is a visco-acoustic polymer that acts as a constrained layer damping material between layers in an acoustic isolation leaf. It CANNOT be used as glue to bond things together. That's not what it is for. Your plasterboard will still need to be attached to the studs in the normal approved manner. Check your local building code for that, to find out what type of fasteners are approved, and what schedule you need on each layer of each leaf.

For the inner leaf ... mounted on resilient channel, mounted on 2x2 studwork.

You do not need both. RC is for cases where the framing is not decoupled. The way you describe it, it will be decoupled, so there is no point in using RC. You would gain nothing by doing that. Also, 2x2 framing would be insufficient to support the ceiling, structurally. You will need 2x4.

I'm planning to do a concrete slab for the floor directly onto compacted hardcore.

... and a suitable DPC! Pouring concrete direct on grade with no barrier would not be good....

Depending on the construction of the outer wall, we may need to dig some footings too.

You WILL need footings, regardless of what the construction is. That's a given. You can't support that amount of mass on a simple flat slab. Perhaps you could do a monolithic slab to save money, but it will still need the structural integrity provided by the foundations.

1. What is the best material to make the outer wall from? I was thinking that using dense breeze block (100mm thick liek this: http://www.wickes.co.uk/Wickes-Dense-Bl ... m/p/113505) may be a good thing to get some good mass into the wall. Is this going to be any better for soundproofing than using SIPS panels or even OSB on a timber frame?

How much isolation do you need, in decibels, and at what frequencies do you need it? Without knowing that, it's impossible to answer the question.

2. How thick should I make my concrete slab?

Yous structural engineer will define that for you, after you show him the plans for your studio. He will calculate the loads, look at the soil in your garden, and figure that out. That's what you'll be paying him to do.

3. What is going to be best for roof construction to maximise isolation? Its going to be a flat roof with a gentle slope to the rear - probably finished with EDPM rubber roof covering.

Once again, that depends on how much isolation do you need, in decibels, and at what frequencies you need it.

4. How large an air-gap should I leave between the 2 leaves?

Ditto. Isolation depends on mass and air depth, cut-off frequency depends on mass and air gap. The equations are simple, but unless you have the numbers to plug into them, you can't get an answer. We need to know how much isolation you need, in decibels, and what frequencies you need it at.

I could probably stretch to 20cm, but 10cm would be better for clawing back some of the inside space

How can you know how much space will be available if you don't yet know what materials you will be using, how dense they will be, or how thick they will be?

5. How should I get the electricity cable into the building without compromising all the soundproofing work?

Between the inner leaf and outer leaf, you run it through conduit that is decoupled in the middle, with a gap between the two sections that is wrapped in a suitable resilient material.

I'll be running armoured cable up from the house - so would it be sensible to get that in before the concrete slab is poured and have it poking up from the slab ready to be connected up?

You could do that, yes. But I would still run it through suitable conduit. I would also run any other cabling you might need through a second conduit, such as phone connection, internet connection, alarm connection, intercom, cable TV connection, etc.

6. Am I in fantasy land that I can do this and achieve enough soundproofing that I could go and thrash about on the drums at midnight and no-one would hear a thing?

To answer that, you'd need to define how may decibels (dBC) is "thrash about on the drums", and how many decibels is "no-one would hear a thing". You need to but your subjective descriptions into objective numbers. There's no place in the equations for isolation and MSM resonance to plug in the phrase "thrash about on the drums.... You can only plug in actual decibel numbers...


- Stuart -

[nick_c]

Stuart - thanks for your quick reply! Apologies - the first thing I did after joining was update my profile with my location, but for whatever reason - it didn't save!

It looks like I need to come back with some hard numbers on things to make it possible for anyone to help. I know 'thrashing about on the drum kit' is totally subjective, but there must be some generally accepted figures for frequency and decibels isolating an acoustic drum kit? Or am I hoping for too much? I'll organise to get hold of a meter, set up the drums and have a good 'thrash'.

Regarding the green glue - of course - I used the wrong terminology - I get that the boards still need to be fixed - but I didn't get that I could fix it directly to the studwork.

Regarding the budget, well - I've got to be creative about it - I don't have £20,000 to spend on this - that's why I'm not handing the whole thing over to a pro to do.

I'm not totally useless when it comes to DIY and light construction - me and my carpenter buddy have just finished renovating and extending the house, so between us we can handle it - hence the lower budget!

Thanks again - and I'll come soon back with some hard figures for you.

Nick

[Soundman2020]

the first thing I did after joining was update my profile with my location,

know 'thrashing about on the drum kit' is totally subjective, but there must be some generally accepted figures for frequency and decibels isolating an acoustic drum kit?

It would be nice if it were so simple..... Imagine a major rock kit, with double 28" kicks, double pedals, a pair of snares, a dozen toms, two dozen cymbals, and played by Dave the Deranged Smashing Gorilla with really loud huge hard sticks, as compared to a small jazz kit, played softly by Timid Tim with brushes... we could talking 120 dB For Dave vs. 90 dB for Tim. That's a difference of 30 dB, with Dave being 8 times as loud subjectively, and putting out one thousand times more acoustic energy. (An increase of 30 db is an increase of 1.000 times the intensity).

On the other end, your neighbors might be absolutely deaf octogenarians who "can't hear a thing" below 70 dBC, or they could be a sensitive baby that wakes up and cries at the drop of a pin...

Very different scenarios there.

You likely also have local noise regulations, which set a legal limit on how you can be, how that should be measured, and the conditions it should be measured under.

In short, you might need 20 dB of isolation, which you could do with a couple of sheets of cardboard, or you might need 90 dB of isolation, which would need massively thick double concrete walls, floated on huge isolation springs....

I'll organise to get hold of a meter, set up the drums and have a good 'thrash'.

Set the meter to "C" weighting, "slow" response, and get someone to hold it about a meter away from the drum kit, at chest height, angled upwards at about 45°. Then trash your heart out! Take several measurements at several different points around the kit, with several different songs. Not the highest measurement, and also the average.

I get that the boards still need to be fixed - but I didn't get that I could fix it directly to the studwork.

They MUST be fixed directly to the framing. I have yet to see a building code that allows the second layer of drywall (plasterboard) to NOT be fixed through the first layer and into the studs (or RC): Drywall is not structural: it can't be used for taking any kind of load, in tension, compression or sheer. It can take small bending loads, but that's about it. It needs to be firmly attached to the underlying structure, using approved fasteners on an approved fastening schedule. When the time comes, don't forget that the fasteners for the second layer need to be longer than those for the first layer, by exactly the thickness of the first layer... Some people forget that, when they buy their nails or screws....

Thanks again - and I'll come soon back with some hard figures for you.

- Stuart -

[nick_c]

Hi again Stuart,

I'm finally back with some data!

I guess I'm not a crazy loud drummer - we got a reading of 103db.

At 10pm I went outside to get an ambient sound reading and got 66db. There's some road noise from a busy road about half a mile away and the neighbour's babbling water feature was gurgling away.

So does that mean that an overall STC value for my drum studio needs to be 37db..?

Thanks,

Nick

[Soundman2020]

At 10pm I went outside to get an ambient sound reading and got 66db.

That's pretty loud for a night-time ambient reading. That's about as loud as a typical conversation between two people at normal voice levels. Surprisingly loud. Are you using a proper hand-held sound level meter? An app on your cell phone is no substitute....

Also, you should check your legal requirements: Your local municipality will have regulations. You will probably find something like 45 dB, or even lower at night.

So does that mean that an overall STC value for my drum studio needs to be 37db..

I would aim for more like 50. That's a more reasonable goal for a drum studio.

Also, it's not STC. It's "Transmission Loss", which is a very different thing. STC is a rating system for typical office, school, hotel, and shop sounds, but no use at all for measuring isolation of full-spectrum music, least of all for drums! Practically all of the energy put out by a drum kit is in the range that STC does not take into account!

So don't base your isolation on any STC numbers. Only TL.


- Stuart -