UK Garage Rehearsal Room

[ady87]

Hello everyone.

My name is Adrian, and I’m writing from Swindon, Wiltshire in the UK. After a year or so completing a house renovation, I’m finally able to begin realising my dream of building a rehearsal space / studio in the detached garage. This was on the cards since the day I made the offer on the property and I would say I’ve been planning now for the past 3 months. I can only wish I’d discovered this forum sooner!

I’m a competent diy’er, and have a background in audio/acoustics from my college days. I’m familiar with the fundamentals but with this being my first audio related build – I’ve never put any of it into practice. I tend to agonise over making decisions when considering things I don’t fully understand, which leads me up to where I am with this project. I am not yet completely clear on my plan, and therefore reluctant to start. I have a copy of Build It Like the Pros which has answered pretty much all my ‘how to build’ questions, but I am struggling to understand how to best apply those techniques to my build in some areas.

The use case – The primary function of my build is to create a great space to enjoy playing music, jamming and writing. The typical set up would include drums, bass, guitars, keys/organs and vocals often in the region of 110db. The secondary function would be to record, though this should not be considered critical/commercial, and would only ever be me recording myself and/or my friends cutting demos etc. On that basis, I’ve made the decision to build one large room.

The main goal - Not disturb the neighbours. The garage is detached, and 32m/105’ from the nearest bedroom window. The garage is however surrounded by gardens, which tend to get used throughout the summer. Background noise levels in the garden and at the back of the house are 50dbA. By my maths I want to be aiming for 60db isolation to keep everyone happy in the summer.
I understand that to achieve good levels of LF isolation I need to build a MSM 2-leaf wall system, with the inner leaf being completely isolated from the outer. From what I’ve learnt so far this should typically involve beefing up the current structure/outer leaf before then building my inner leaf room. I see this project consisting of three main stages;

1 – treating thing outer leaf / existing structure
2 – designing / building the inner / leaf room within the available space
3 – treating the inner room acoustically

My focus is to ensure I dedicate enough time and resource to ensuring each stage is done right. I don’t need to complete all 3 stages in one go, and would sooner focus on getting the best result in stages 1 and 2 before tackling stage 3 later down the line. I currently have £6000 ($8500) put aside for this project.

Onto my problems! The garage is not a great starting point. It’s a pre-fabricated structure made up of steel framing, concrete wall sections (2.8” thick edges with recess to 2” in the middle) and a timber top with gaps everywhere. The garage roller door spans the width of the garage with no other entry point. There are timber doors and 2 single glazed windows on the back wall out to the garden behind. The only access to this garden is through the garage.

I have already built an exterior stud wall that sits in front of the roller door. This is made up of 3x2 stud work, moisture barrier, 5mm ply and finished with tongue and groove cladding that fits with the rest of the building. I had considered keeping the roller door, and enabling it to shut in between the two leaves for additional security should I go on holiday. This limits how thick that front wall can be of course, and if it’s going to be problematic, I’m happy to remove it all together.

I intend to use FD30/60 fire doors which I will super door if needed. The rear door may need to remain split in the middle so as not to hit the steps up to the decking immediately behind. It would be nice to keep some natural light, but I have no issue with blocking up the windows if they’re going to be a big weak point.

Here’s a sketch showing the garage structure, dimensions are internal indicating the available space within the room.

1 garage dimensions.png

and here are some photos of is as it is;

2 front.jpg

3 front-internal.jpg

4 wall structure.jpg

5 gaps.jpg

6 rear door.jpg

7 roof structure.jpg

My initial plan was to densely insulate the stud / concrete sections to bring the walls level to the steel uprights. I would then add drywall to create a nice tight seal all round. I now understand this will create a 2-leaf system, and once my inner room is built I’ll have 3 leaves.

So, what I think I should be doing is;
- Infill 3” stud sections with at least 2 layers of dry wall, backer rod and caulk
- Infill gaps between concrete and timber sections with backer rod and caulk
- Insulate on top of all that

My concern is just how ‘gappy’ the wall currently is, and that even with beefing up treatment I’ll still be left with a large area of weak points. Any other ideas on how best to approach this?

The ceiling seems to be my main issue. The corrugated roof is supported by timbers on 3 steels spanning the width of the room and there seem to be two options;
1. Keep the pitch and add dry wall to the timbers in-between each steel section. Looks like it could be problematic to get a good seal between dry wall sections, where the dry wall butts up to the angled steel, particularly on the flat side.
2. Keep the pitch and add drywall between the roof timbers, pushed up against the corrugated material. Should be easier to get a good seal as the dry wall would run over the steels as per the timbers. The centre point at the top of the pitch looks problematic as there is not a single timber in the middle, but two positioned closely together.
3. Create a flat false ceiling by hanging stud framing from the steels and edges of the room. This would give me a completely flat area that would be easy to dry wall and seal. But is this then a 3-leaf system?
Either way, I have slight reservations in hanging all that dry wall to the ceiling, though my builder friend insists there’s nothing to be worried about and the steel framework will more than capable of handling it.

Once the outer is sorted, I’ll then look to design my inner room. Initial planning looks like it will be difficult to avoid modes as I don’t have the height to maximise my length and width and maintain a good ratio. A problem for another day.

Any suggestions or guidance on how best to approach this first stage would be greatly appreciated!

Thanks,
Adrian

[Gregwor]

I will have a similar issue with my garage ceiling. From the research I've done, and to have a comfortable building, you will need insulation in the "attic" with air flow in it. Therefore, I think you might be best to throw two layers of 5/8" on, making a flat ceiling, then build another ceiling under that that sits on your inner leaf. You'll definitely need to talk to some structural engineer to figure out how to create your inner leaf ceiling so that it can hold up another few layers of 5/8" drywall. Of course, doing it inside out would be ideal. I posted an MSM calculator on the acoustics page yesterday. You should type some densities and wall cavity depths in regarding your outer leaf question to ensure that you'll get the isolation you're after.

Regarding your dimensions and "avoiding modes" comment, if you search the forum some more, even recent posts from the last few days, Soundman2020 has posted lots proving that you want as many modes as possible! The biggest two things to avoid are having modes that are bunched together closely and do your best to have the lowest Schroeder Frequency possible (that last one comes with room volume... bigger the room, the better). No multiple (for 5% of multiple) dimension relationships. Other than that, your acoustic treatment will just eat up a butt load of your space as the deeper the absorption, the better to dampen the low frequencies which will stop them from ringing so long.

You also may have to add more mass between your 3x2 studs on your new door wall. You can calculate that with the calculator I mentioned above. Regarding the dual door situation, I've seen it done in lots of high end studios. You may just have to have insanely beefy doors with crazy seals and of course maybe one single massively heavy door on your inner leaf. Consider your HVAC in your design too. Your outer and inner leaf relationship can drastically change because of it. You can probably use your attic to house most of that stuff.

Greg