Soundproof your shed

[BRG1200]

Guys,

this is a snapshot of a conversation with a guy where I work, amongst other things he’s a musician and has long been involved in local bands and venues. It’s long, so I’ll break it up to fit in a forum topic format.

My reason for asking his advice was to find practical advice on how to “soundproof” my sheet metal garage as far as practicable. I had my own ideas, but figured he would have been there and done that many times before. My garage is right next to the neighbouring house, which is built very close to the property boundary.

I figure that I cannot be the only guy on the forum looking to attenuate the sound from the garage or similar, and therefore be able to do a bit of work in the evenings or generally do noisy stuff without disturbing neighbours.


The conversation:

You've asked the right person, that's for sure.

I'm in the process of soundproofing my home recording studio which is a carport under main roof, enclosed with simple stud wall with cement sheeting exterior, plasterboard interior.

You need two things: mass, and mechanical isolation.
Mass comes in the form of high-density mineral wool. Bradford Insulation makes a form of rockwool, I can't remember the product code right now but I can dig it up. Acoustic absorption requires a mineral wool density of 30-40kg/cubic metre, I don't remember the precise figure. Bradford's batts are categorised according to density.

Basically you need to fill every cavity, every void, every nook and cranny with mineral wool at least 45mm thick (90mm is better).
If your studs are 90mm then you should be ok.
Mineral wool is quite thick and resilient, it should stay in place as semi-solid slabs. You cut it with a bread knife.

[BRG1200]

The first thing to do is seal every exterior crack and gap with polyurethane sealant or similar. You can do this on the inside face of the steel sheeting so the exterior of your shed doesn't look like crap.

Then erect the stud walls and fill the cavities with mineral wool. The ceiling might require fishing line or thin wire to hold the insulation between the joists.

For the best possible isolation, mount your MDF sheeting on resilient channel, NOT direct to the studs.

Resilient channel is designed to acoustically isolate the stud from the wall sheeting. You have to be very specific when ordering resilient channel from a supplier - some will try to sell you "hat" channel which is not acoustically rated.

You have to be careful not to screw your wall sheets all the way through to the studs - this will ruin the acoustic isolation.

Lastly you need to seal every crack and gap in the wall sheeting.

Imagine a 5mm crack, 3m long. That's the same as having an open window.

Install the beefiest solid-core door which the frame will support, and seal the edges with rubber flanges/weather seals.
Two doors is even better.

You need to consider HVAC as well. You're basically building a super-airtight box, you MUST have fresh air intake and stale air outlet. The simplest way to do this is to install a fan-powered fresh air vent at one end of the room and a passive stale air vent at the opposite end. Because the room is airtight, the stale air will naturally find its way to the outlet due to the room being at a positive pressure compared to the outside world.

[BRG1200]

> Thanks for that, you completely get where I'm coming from.

> I think I'll start a forum topic on my favourite motorcycle forum on this!

> I find that if you talk to an Acoustic Engineer from our position as a project officer you just get a fee proposal for 2 or 3 grand, but there have to be simple basic principles and product knowledge, just like any other subject.

> I was thinking of lining the roof to a degree as well, but with plasterboard (or even cement sheet) for lightness rather than try to use the MDF I have or the Chipboard I can probably get in future. I also want to mount things (shelves etc) directly onto the walls, so MDF and chipboard are ideal in that respect, better than plasterboard.

> My garage is a simple, 36 sqm, square, ridge-roofed structure.

> Right now I have enough MDF sheeting to cover at least one side wall of the garage, was thinking of gluing some fairly heavy sheet material directly onto the sheet metal to prevent reverberation/transmission. Then insulation, and I was about to start looking at spray-on insulation, as it will all be covered up in any case. Spray on would effectively seal a lot of gaps but yes, the structure is very permeable, as I've discovered from shredded leaf litter constantly blowing in.

> Top tip on the Resilient Channel, I'd never heard of that.

> Ventilation, I was thinking of a couple of those roof whirligig jobs to keep the place cooler automatically, but they would leak sound massively. I reckon a couple of carefully positioned electric fans as you suggest.

> Do you reckon a certain amount of the shaped foam stuff I mentioned might assist in reducing internal noise levels? (The sort of wedge shaped foam you see on music studio walls)

> I was going to go ask at a music shop, where to get, how much, what use, and so forth.



Most "acoustic foam" is pure marketing hype.

Foam offers very little acoustic absorption where you need it most: 20-1000Hz (i.e. where most machine & plant noise is).

Foam will only absorb higher frequencies, making the room sound boxey, woody and lifeless. It's also dangerous because it gives the illusion of reduced volume, which might cause you to go even louder.

Don't waste your time talking about foam in a music shop - they'll just try to sell you a bunch of unsubstantiated B.S.

Beefing up the outer leaf is a good idea.

You can't escape the laws of physics: more mass = more acoustic isolation.

The maths is pretty easy. A typical power tool or machinery generates about 100-120dB of noise at the source. 30-40 dB is generally the typical suburban ambient noise in the middle of the night (same as a very quiet library). So, you need 60-70dB of attenuation to get your machine noise down to 30-40dB immediately outside your shed. Realistically this means you only need about 40-50dB of attenuation when you factor in that your neighbour's walls will provide another 30-40dB of attenuation. 40-50dB of attenuation is achievable in a simple 2-leaf single stud wall such as a shed.

[BRG1200]

16mm plasterboard (such as Firechek) should provide about 30dB of attenuation on a simple stud wall. Each additional layer of 16mm plasterboard should provide another 6dB of attenuation.

If you adhere the layers using a product called Green Glue then the attenuation increases dramatically.

Green Glue acts as a resilient layer, it never fully dries but remains slightly tacky, allowing the sound to be dissipated as heat between the layers of plasterboard.

If you find a single layer of MDF or plasterboard on resilient channel is insufficient for your internal walls then you could add a layer of plasterboard and green glue.



You'll need to fill the gaps where the roof corrugations meet the walls. I used Firestop putty to seal the corrugations on one of my sheds in addition to sealing every single lap joint with polyurethane sealant on the side sheeting. There was a tiny pinhole leak in the roof which I missed, didn't realise until the rain got in. Apart from the leak, the shed was so air tight that the whole thing became mouldy over summer and I had to leave a window permanently open to get some air flow.

You DO NOT want to get mould in your walls, especially with MDF or plasterboard. Air circulation is vital.

[BRG1200]

The foam wedges I am referring to are the things I've seen lining the Uni's anechoic chambers, other similar chambers, music studios. But I take your advice, there is plenty to do immediately, internal baffling or absorption would be the cherry on top.

Preventing the outer sheeting from vibrating and allowing sound through in that way seemed likely to be productive, a layer of something fairly "heavy" direct-stuck on the inside of the sheeting seemed likely to dampen that potential.

The Resilient Channel to isolate the internal sheeting is a great idea, if it does what I imagine then that would be a big help.

Typical noise I will be making that would get straight through currently:

Tapping & hammering, metal on metal.

Domestic power tools, circular saw, drills angle grinder, dremels etc

If all goes to plan I'll eventually get a compressor (takkety-takkety motor noise) and a small sand blasting cabinet (I imagine considerable "hiss"), but that will be a different kettle of fish, was thinking of applying something onto the cabinet, and building an enclosure around the compressor.

[2TInstitute]

Some good info there, but I must have tollerant neighbours, I find noise during the day not really a problem unless it goes ALL day. Keep the power tools to a minimum after 6 and not after 9pm. Lathes and milling machines are fine, welders no problems unless your on AC. Failing that hand out ear muffs

[BRG1200]

Seal all gaps in metal shell of the garage.
Magic Ingredient: Green glue MDF panels to inside of steel sheeting, to prevent reverb (or whatever the term should be) of the sheeting.
Construct a timber stud frame, "isolating" vibration where possible.
Pack cavity with the insulation you specified.
Add magic ingredient: Resilient Channel.
Sheet with MDF/Chipboard/16mm firecheck as available.
Seal all edges and joins.
Maybe put an extra layer on the wall facing the neighbours, using Green Glue.
Seal all edges and joins again.
Install carefully directed ventilation.
Carpet the concrete floor.
Add whatever sound absorption I can to inside surfaces.
Buy a drum kit*.


* Drum Kit Optional.

I used something that sounds like Green Glue years ago in a load spreading activity. I needed to put large box section steel "skis" down in order to place huge Lektriever storage systems on the slab.
Seem to remember it was a bottle green colour with bubbles in it, the stuff took up any variation in the surface and glued the "skis" in place for good. It was an industrial strength construction adhesive.

[BRG1200]

Well Mr Institute, you are luckier with neighbours than us. I won't go into it but they have been a big problem over a very long period. Which recently resulted in us getting an intervention order on them.

I figure going to great lengths to soundproof the garage is well worth it, but also I can't be the only one around here who would find this info useful.
In the UK, at least the area I lived, people live extremely close compared to Australia. Garages, where they even exist, are generally part of the house - brick built, and separate sheds and garages often built with brick, cement block or wood. I was really surprised at just how little sound was stopped by the walls of my new sheet steel garage here in Australia, virtually none.
Having a garage at all in many parts of the UK is an expensive luxury, you Aussies could be surprised. Enjoy your big sheds and wide spaces you lucky people.

[Jeram]

is it running bikes that is causing the sound or general tinkering in the shed?

Either way, if its a big shed why not just create a sound box in one section of the shed where you can go into to fire up bikes, do grinding etc.
(similar to a dyno room set up)

That would save ALOT of money!

Times like these Im glad my shed is double brick! and my neighbour is a 90 year old lady who just so happens to be deaf! haha

[BRG1200]

Jeram, you’re on my wavelength, and that’s the current plan. A 3 metre by 3 metre “room within a room”. Garage is 6 metres by 6 metres. Drawn up a plan.
And yes, it’s any grinding, hammering, woodwork involving compound mitre saw etc.
Have demanding young kids and cannot, just cannot, get at anything in normal hours, so while the really noisy stuff would have to be normal hours any generally noisy stuff I could do in an hour or two in the evening would be fantastic progress.
Interesting subject, learnt a lot in a few days reading and talking to people.

[Jeram]

grinding and other high pitched sounds will be a peice of cake to mute, but hammering it much harder as its contains alot of low frequency sound waves which are harder to mute.

Low pitch waves are the ones which can escape through tiny gaps and holes, which is the same reason why low pitch sounds always travels further before they dissipate.

[BRG1200]

Acoustic materials are expensive, an effective 4.5 sqm of 110mm insulation bats is $50, so in acoustic bats my proposed box in the garage would be about $900 if my maths is right.
The Green Glue is as far as Zi can make out so far, about $40 for a tube the same size as a tube of silicone sealer. I wonder how much difference it makes and how much you'd need to use.
Resilient Channel I haven't found yet.

[TZR250]

as a drummer i made a little room in my shed

ended up with carpet hanging off the walls and egg cartons on the ceiling but thats for music no good for a workshop

most effective is solid so brick or concrete i would believe for a workshop if your talking late after hours