Garage Conversion

Hi all, I’d love some advice and feedback before heading into my project: Background: I have been reading the forum for years now and I'm finally at the point where I’m ready to plan and build a studio of my own. I previously lived in a 2 bedroom flat and used the spare room for my studio which I treated but did not soundproof at all. This, as you can imagine, didn't go down too well with adjoining neighbours at times! I have now moved into a detached property with integral garage and I’m ready to convert the garage into my studio. The previous owners had done a half-hearted job at a garage conversion - they had a stud/insulated wall put up inside the garage door and ‘dabbed’ plasterboards up all round followed by a light skim and all finished with thick royal blue silk paint! The room also has a radiator and lights/power sockets etc. The boiler was also in there but I have had a new combi-boiler put into the loft of the main house, so it’s gone form the garage now. I noticed the advice to purchase a sound level meter and I have now ordered one ready for when the project begins - I would like to keep track of the ‘before’ and ‘after’ in terms of isolation. Purpose of the room: The room will be used for recording, mixing, video editing and some studio photography. I plan to have my desk at the garage door end of the room with speakers facing into the length of the room. Since getting the keys I have removed all the plaster/plasterboard from the garage walls and ceiling so I’m back to bare concrete (insulated blocks) blocks on the inside, with the outer structure made up of standard house brick. The size of the garage internally now is - 5050mm Long x 2400mm wide x 2530 High. The garage also has two double glazed windows: Plans and approach: Here's what I plan to do, together with a few questions in areas where I'm struggling design/construction wise: The first step is to have the garage door opening properly bricked up and to ensure that any other holes are bricked in (like where the boiler sat on the wall). I’m using thermalite blocks and will also be putting a DPM down. The next thing will be to stud out the walls with timber all round. I plan on using 75ml thick insulation for inside the stud - Earthwool - I will also use this mineral wool as part of my interior acoustic treatment when I get that far. After the stud - I Will use resilient channel/bars to separate plasterboard from the stud structure. I have not yet found the exact product to use but I have seen some examples with and some without the use of whisperclips/ isoclips which are seemingly very expensive. I plan not to use these if it's agreed that I can achieve good isolation without. I'm going to use two layers of plasterboard off-set from each other with GreenGlue between the two layers. I will use one layer of 15mm thick standard plasterboard, and one layer of 12.5 mm sound/acoustic plasterboard. Each layer will be filled/sealed on all seams and I'll also use backing rods and caulk between the floors, walls and ceilings to decouple them from each other. The floor is concrete and I plan to float a stud floor on u-boat type pads. This structure will then be topped with chipboard flooring panels. The floor structure will not touch the outer stud structure of the walls, but the plasterboard will sit in line, with backing rods and caulk used to join and seal the walls to the floor. On to the ceiling. The structure has a pitched roof with ceiling joists running the length of the garage. I plan to use resilient bars hung to the joists to again hang two layers of plasterboard and, as before, I will use the earthwool above in between the joists. As an approach I plan to hang the first layer of plasterboard on the walls, then the ceiling, then fill/seal seams, then backing rod and caulk around the edges, then move on to the second layer of plasterboard going at it in the same order. Below is a view of the ceiling space: Where the windows are situated I plan to add a third pain of glass on the inside of the structure obviously sealed air tight. I would hate to lose the daylight that the room gets, but of course I don’t want the windows to ruin the rest of the build in terms of performance. Concerns about the new structure: We're working hard here to add mass as well as decoupling to prevent sound from travelling through walls. What is the best way therefore to get the power into the room without compromising the structure? I have struggled to locate/understand this info. Obviously making holes through is going to compromise things, so what’s the solution? I have seen info regarding putty pads etc. also some advice on running electrics using conduit inside (surface mounted) the room rather than through the walls, but I could do with some simple advice to consider the options here. The consumer unit for the entire house mounted on the garage wall currently. This also needs to be considered – how to box in or have remounted on the internal structure. This may also be upgraded to a more modern box, after having spoken to my electrician. The room also has had a radiator in there - It would be good to keep the pipes and add a new rad on the interior of the room once the new structure is finished, but again, what’s the best way to get the pipes into the room to avoid compromising the wall structure? The final concern is around ventilation. Having seen a few examples on the site I don’t know whether to just have a portable air-con unit, or whether to build an intake fan with the S-shaped soundproof case to draw fresh air into the room. Again here though I’m worried I will compromise the structure if I don’t execute this correctly. Budget: I have costed most materials online and have come up with a figure close to £1500. This figure does not include the green glue (still looking for best price), window panes, new rad, aircon or ventilation. As an upper limit - I can see a bit of movement in this figure and could allow it to creep to £2000-£2500. I have also had an estimate from the electrician of around £800 to move the consumer unit, swap with a new one if required, and to provide 6 LEDs and 4 new double power sockets – one for each corner of the room. Also not included here is the costs associated with treating the room once the isolation/soundproofing stage is complete. Questions summary: 1: What are the available solutions for getting power into the room without compromising structure and isolation? This includes the existing consumer unit problem. 2: In the same way, what’s the solution for getting my heating pipes into the room? 3: Given the type of construction, budget, ideas I have put forward what would be recommended for ventilation? 4: Given that I’m decoupling the walls from ceilings and floors, how do you go about adding skirting boards to finish the room again without compromising what we have achieved and re-coupling them together again? 5: Are 'WhisperClips / IsoClips / GenieClips' fundamental? 6: finally, do you have any concerns or ideas to improve my plans before I look to purchase materials etc. Thanks in advance, help and advice is very much appreciated. P.S. the file attachment option doesnt seem to be working for me right now, the upload progress bar seems to get stuck - I will attempt to upload the images again later.

Images attached, thanks for looking. Regards, Marc

Ok so I have started to make my way through the content of Rods book and already spotted a key mistake. I mentioned in my write up about creating a floated stud floor unit and it seems Rod strongly advises against this, and actually it makes complete sense. If any of you guys can provide further advice here, that would be good. Given this approach is a no go, how should I approach the floor? Any help with the other areas I have highlighted above would be good too. Thanks in advance Marc

The book has also answered my questions regarding the whisper / ISO clips too which is great. I hadn't realised the difference between hat channel, Z-channel and proper resilient channel. It may sound dumb, but I just didn't know. You live and learn! I'm glad the learning is happening now and not after purchase, or even worse - after install!! Regards :)

Ok, so im now reading all the info from this thread and discovering that in basement concrete floors the use of rockwool filled stud floated floors are of benefit... I assume this would also be the case for a concrete garage floor?

Im now looking at two potential wall, floor set-ups. Any feedback on which would be better would be good:

Heres a (very basic) visual on the otpions in my head for the ceiling. again, feedback on which provides better isolation from the outside world would be great. not sure if option 2 constitutes '3 leaves' or not...

Hi there, great to see another UK poster I am not an expert but have been reading through your posts and think before you do any more I would try to get one of the mods to answer as there could be some potential problems with some of the things you are planning I think. Also although youve said what the room will be used for recording , mixing etc you will need to know what sort of level of noise that is? So when recording is that gonna be full drum kit/ Bass/electric guitar? How close is your nearest neighbour and what about the rest of your family and the bedrooms/living rooms so you can get an idea of the amount of decibels of sound that you are gonna have to isolate, As for the 2nd layer of plasterboard just use the 15mmm thick as the first layer is the usual advice, more mass which is better,

Roguejackal: Thanks for the response, much appreciated, and yes I completely agree - I'm holding off from purchasing while I wait for some input from the mods. Im also worried about the lack of space that the designs above lead to. I'm wondering whether an inside out design may be better therefore. In the mean time here's some of that basic info: The majority of the music I create is electronic - pop, hiphop & dance. I don't use live drums, its all programmed with software. I do record live guitars - acoustic and electric, and I'm always recording vocals. I have only one neighbour to worry about really - the garage is around 2-3 metres from them to the right of the house. The next nearest is on the opposite side of the road in front, quite a distance away (maybe 10-15 metres). I live alone (with my bulldog) - so I dont have to worry about the house, my main concern is to not annoy neighbours. Thanks again.

Hi there, Il give you my input from what iv learned but like I said I'm not an expert so don't take everything as gospel :D Quote The majority of the music I create is electronic - pop, hiphop & dance. I don't use live drums, its all programmed with software. I do record live guitars - acoustic and electric, and I'm always recording vocals. sounds a little like my stepson although he is more drum & bass or dubstep an mainly synths,drum machine etc so probably majority of the time your gonna be mixing at around 85db might be a little higher occasionally, so that is good for you, I would say your main problem will be the bass with hiphop and dance music. Quote I have only one neighbour to worry about really - the garage is around 2-3 metres from them to the right of the house. The next nearest is on the opposite side of the road in front, quite a distance away (maybe 10-15 metres). 2-3 meters is better than nothing but your build will have to be done right mainly for the bass so you don't cause any fuss with the neighbours, so I would say you need to aim for at least 50db of isolation, your biggest problem will be the windows unless of coarse you take them out and then brick and block them up completely :shock: With your floor just a decent laminate floor on the acoustic underlay recommended is fine, (green fibre board in stores) Im sure if you have a search on the forum you will probably find a few builds that have been done in a garage or are on the go at the moment. I can understand your concerns about how small the room can get so I would check out Johns inside out design and read some of the builds that have used this method, it brings its own problems in the build which I decided against for me but may be ok for you, however all my interior walls in my control room are pretty much covered in insulation and then material,

Hi there Marc, and Welcome! :)

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Ummm... little problem there! It's not much use posting the location of the images on your own hard disk! :) We can't see them like that... To upload an image, click on the "browse" button next to "Filename" just under the text window when you are writing a post, then go to the directory where the image is, click on the image, then double-click on the image, then click the "Add the file" button and wait for a couple of seconds while it uploads.

I plan on using 75ml thick insulation for inside the stud - Earthwool -

What density are you planning to use? That's important...

After the stud - I Will use resilient channel/bars to separate plasterboard from the stud structure.

Why? If your stud frame is decoupled from the outer-leaf concrete block wall, then you do not also need resilient channel (RC). That's for situations where the framing cannot be decoupled, for whatever reason, bur since you are building it yourself, there's no reason why you can't decouple it. There's no point to decoupling twice. IT's a waste of money, space and effort.

I plan not to use these if it's agreed that I can achieve good isolation without.

As long as you ensure that your inner-leaf framing is fully decoupled from the outer-leaf, then you are fine.

I will use one layer of 15mm thick standard plasterboard, and one layer of 12.5 mm sound/acoustic plasterboard.

make them both 15mm. The 12.5 stuff is too thin, too flexible, to light weight. Yes, there is a slight advantage due to having different impedance and different coincidence dips with two different thicknesses, but in reality it is more than offset by the extra mass and thickness.

The floor is concrete and I plan to float a stud floor on u-boat type pads.

:shock: Bad idea! You already have a great concrete slab on grade for your floor: why ruin everything by "floating" badly? You might want to read this: viewtopic.php?f=2&t=8173

Below is a view of the ceiling space:

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Ummm... I'm sure you are seeing the images on your own disk, but we aren't! see above... :)

Where the windows are situated I plan to add a third pain of glass on the inside of the structure obviously sealed air tight.

That would make your window into a 3-leaf system: bad idea. That will REDUCE isolation in the low frequency end of the spectrum, not increase it...

I would hate to lose the daylight that the room gets, but of course I don’t want the windows to ruin the rest of the build in terms of performance.

Then do the window as a proper 2-leaf system, not a 3-leaf system. 3-leaf always isolates worse than 2-leaf, all other factors being equal.

What is the best way therefore to get the power into the room without compromising the structure?

Like this: Electrical conduit (PVC) bent to shape, then cut out a section a few cm long, and wrap the gap with Neoprene, EPDM or Sorbothane rubber sheeting, then seal it. Use Putty Pads (a.k.a. "Putty Packs") on the penetrations where the conduit passes through the drywall.

Having seen a few examples on the site I don’t know whether to just have a portable air-con unit, or whether to build an intake fan with the S-shaped soundproof case to draw fresh air into the room.

Actually, you need both! The air conditioner cools and dehumidifies the air but does not bring in fresh air or take out stale air. The ventilation system brings in fresh air and removes stale air, but does not cool or dehumidify. So you need both. You also need to calculate how much air you need to move through the room, and what speed to move it at, so you can figure out what duct size you need, and what fan you need. HVAC is a bit more complex than most people realize...

Again here though I’m worried I will compromise the structure if I don’t execute this correctly.

Yup! That's why you need silencer boxes on your ventilation ducts. Here are some examples of what people have doen in their studios to build their own silencers: viewtopic.php?f=2&t=15430&start=45 viewtopic.php?f=2&t=1929&start=74 viewtopic.php?t=8425&start=2 viewtopic.php?f=1&t=11542&start=5 viewtopic.php?f=2&t=9761&start=0 viewtopic.php?f=2&t=11485&start=98 viewtopic.php?f=2&t=11508&start=157 viewtopic.php?f=2&t=13821 viewtopic.php?f=1&t=15378&start=44 viewtopic.php?f=2&t=18202&start=16 That should get you on the right track!

3: Given the type of construction, budget, ideas I have put forward what would be recommended for ventilation?

That is based on room occupancy (how many people you will have in the room, max, and how hard they are working), room volume, and your location on the planet to a certain extent. There are tables that show roughly how many "room changes per hour" you need for different types of rooms, and equations that you can use to refine that further. But as a very rough rule of thumb, plan on doing five to ten room changes per hour. So figure the volume of the room (in cubic meters or cubic feet) multiply by the number of changes per hour, and that's your flow rate: you need a fan that can move that much air per hour. Fans are normally rate as being able to move X-many Cubic Feet per Minute (CFM) of air, so look for fans that can move your amount of air. But that's not all! Fans only produce their rated air flow in free air, with no duct: put them in a ducted system, and the flow rate drops, depending on how much "static pressure" the system has, which basically means how much it resists the flow of air through it. So you have to calculate that, and find a fan that can move that much air at the estimated static pressure of your ducting system and room. For example, a fan might be rated at 250 CFM, but only be able to move 180 CFM with a static pressure of 0.5". So be careful there: do the math, and get the right fan. If you overload a fan with too much static pressure, it will not only not move enough air, but will be much noisier, use more power, be less efficient, and burn out sooner. Then, with all that figured out, you need to do the calculations to figure the duct size: you want the air flow speed to be less than 300 feet per second (fps) where it leaves the register. Since you already know how many cubic feet per minute you need, and how many feet per second you need, it is now simple math to find out how many square inches of cross section you need for your ducts.

4: Given that I’m decoupling the walls from ceilings and floors, how do you go about adding skirting boards to finish the room again without compromising what we have achieved and re-coupling them together again?

Your entire room is decoupled, except for the floor, but all of it sits on the floor anyway, and the floor is very massive (concrete slab on grade) and very well damped (you have the entire planet on the other side to damp it.... that's hard to beat!), so you don't need to take any special precautions between the walls and floor. That would only be necessary if you floated your floor and walls independently, but then you'd be talking about a budget of many tens of thousands of pounds, so I don't think you want to go there... :)

5: Are 'WhisperClips / IsoClips / GenieClips' fundamental?

Yes, but only where they are needed! You don't need them on your walls, and can probably do without for your ceiling too, if you build it as a new frame on top of your new walls...

6: finally, do you have any concerns or ideas to improve my plans before I look to purchase materials etc.

Ummm... Yup! Don't take this the wrong way, but before you buy anything I'd suggest that you do a complete design of everything! Do it in SletchUp (which is an amazingly useful tool for designing studios, and is free!), and make sure you account for every last detail: framing, drywall, HVAC, doors, windows, seals, electrical, room ratio, room geometry, layout, treatment, etc. Put every last detail in there, and make sure it all works together, then check it twice. Then, and only then, buy materials and start building. It's a huge mistake to build before you have a complete, accurate and detailed plan in place. Take a look around the forum and you'll see the many disasters that happened to people who did that... That's not a place you want to be.

Images attached, thanks for looking.

Aaaha! So it worked in the end! That's good news.

k so I have started to make my way through the content of Rods book and already spotted a key mistake. I mentioned in my write up about creating a floated stud floor unit and it seems Rod strongly advises against this, and actually it makes complete sense.

:thu: Yup.

Ok, so im now reading all the info from this thread and discovering that in basement concrete floors the use of rockwool filled stud floated floors are of benefit...

That's a really old thread... And several years later Keith wrote that other post I linked you to, on why its a BAD idea to float a floor... Roguejackal is spot on with all of his comments, by the way! - Stuart -

Thanks for this guys, much appreciated. I'm going to do two things now - work on the design in sketchup now I have the answers above, and while this is happening I can get the garage floor levelled out ready as this needs doing regardless. I have already had the garage door bricked up ready, but will wait now until everything else is designed. Will post up the designs as I get things built in sketchup. Thanks again Marc

Guys if you couls cast your eyes over this initial design, that would be great. I have decided, due to lack of space, to go for the inside-out design that I have been reading about. With this approach this gives me an internal space of approx - 1969mm wide x 4817 in length x 2218 high. Previous design approach would not have been as effective from a space point of view. Here are the initial images from sketchup... notice the waste pipe which has led me to close in from one wall further. Apologies if this should be in the design forum but was keen to continue this thread and not create a new one. thanks marc

Just to confirm - that was obviously me above, must have auto signed out! doh!

Just wondering about your ceiling plan: Instead of putting nailing strips on the side of each joist, and attaching the drywall inside each stud bay on those, it would be an awful lot easier to just put the drywall directly on top of the joists, nailed down into the joists. You also need some type of cross bracing on those joists, to keep them from bending, warping, and twisting. Normally that's at each end of the joists, and also every 16" o 24". The end pieces also serve to seal up the gaps between the drywall and the top plates. - Stuart -

Hi, thanks for the quick response. There's a couple of reasons for the ceiling really - 1 is that this way saves a little space height-wise and 2, I'm struggling to see how I would physically nail the plasterboards to the joists on top. Agreed it would be much quicker etc but not sure how I could get up there, particularly as I got to the last piece. Will add the cross bracing to the plan then - thanks for that! :) Thanks

Guys, I have been thinking through the design more, particularly thinking about the construction phase and actually putting this together, and as the room has a very similar width to height, the usual method of - creating the inside-out frames on the floor, adding plasterboard + insulation and then lifting the wall up from the ground into place - won't be feasible. If I built the whole wall on the floor, theres no room left to get behind it to flip it into position. Hope that makes sense. Given this, I have attached my SketchUp file for a proposed solution - buiding smaller sections of the long walls and lifting them into place one by one. The design animates to hopefully get this across (I have not yet added the plasterboards and insulation on this SketchUp design just yet as I wanted to see what your thoughts were first). The only problem I see is where they connect together. Maybe by overlapping plasterboards across sections would solve this, but please do let me know what you think. Edit - The other thing I have added here are some ideas for flush mounting the speakers, some slots and bass traps (all rendered pink in the file attached). Any feedback on these designs would be great. Again, its tight for space but Im trying to make use of it... Questions: 1: Will the propsed frame solution work - ie creating sections of walls and joing them up - as in the sketchup file? 2: If so, should I overlap the plasterboards between sections? 3: What do you think of the propsed layout? Space is at a premium here and I'm struggling to come up with a better layout. 4: I would like to flush mount the speakers which you will see in the design (not a finished design just the framework), does this look ok? 5: The bass traps at the back (by the doorway) I intent to do superchunk style - is this ok? 6: Thinking about the slot resonators - the fact that one side has the window and therefore they wont be completely symmetrical, will this be a problem? 7: The existing structure also has lots of air bricks. Do I need to block these air bricks to make the external structure more air-tight? 8: (last one I promise) - I plan to build my internal room with new ceiling joists resting on the internal stud walls. What should do with the existing joists? The existing structure at the moment has a pitched roof (not show in diagram) with ceiling joist running the length of the room (shown in diagram). Do I need to plasterboard them underneath sealing the edges to the existing outer brickwork in order to create an air-tight outer structure? If so, should I fill them with rockwool and also place loft boards on top, or would this make it a 3 leaf system (see image below)? Im trying to think of the best solution to ensure that the existing structure is air-tight before I progress with the inner room. Hope that makes sense. Regards, Marc

Hate to be impatient but, BUMP...

If anyone can help with the following questions that would be great: 1: Will the propsed frame solution work - ie creating sections of walls and joining them up - as in the attached new sketchup file? 2: If so, should I overlap the plasterboards between sections? 3: What do you think of the propsed layout? Space is at a premium here and I'm struggling to come up with a better layout. 4: I would like to flush mount the speakers which you will see in the design (not a finished design just the framework), does this look ok? 5: The bass traps at the back (by the doorway) I intent to do superchunk style - is this ok? 6: Thinking about the slot resonators - the fact that one side has the window and therefore wont be completely symmetrical, will this be a problem? 7: The existing structure also has lots of air bricks. Do I need to block these air bricks to make the external structure more air-tight? 8: (last one I promise) - I plan to build my internal room with new ceiling joists resting on the internal stud walls (see file). What should do with the existing joists? The existing structure at the moment has a pitched roof (not show in file) with ceiling joist running the length of the room (shown in file). Should I need to plasterboard them underneath sealing the edges to the existing outer brickwork in order to create an air-tight outer structure? If so, should I fill them with rockwool and also place loft boards on top, or would this make it a 3 leaf system (see file for example)? Im trying to think of the best solution to ensure that the existing structure is air-tight before I progress with the inner room. Hope that makes sense.

Hi Marc I downloaded your SketchUp but can't open it as I'm still on version 8 (the laptop where SU is installed is still on OSX 10.6.8 and SU vers.13 is not supported unfortunately !). But even going in the dark without seeing the design, if I understand well your question about splitting the wall in two section and then joining them together, I proposed these 2 ideas on this thread: viewtopic.php?f=2&t=18242 …hopefully they are pertinent here, or, if they're not ... sorry :oops: ... but I hope at least they'll give you the inspiration for new ideas :-) Good luck ! Ciao Simo

Simo, Thanks for this, I'm liking option 2 a lot, hadn't thought of this! Great stuff. Thanks again.

Ok, I am still waiting for answers from my last post, but will move forward and perhaps focus on a different problem for a little while. Again, I have not started the build yet, so still very much in research mode! Back on to HVAC: I have had a couple of guys round re air-conditioning and ventilation this week to look at the garage and to suggest ideas. They aren't studio experts at all, just local air-con companies, but one has experience working in a school recording studio environment recently. However, I'm keen to make sure I know what im talking about when requesting quotes etc. Stuart (or anyone else out there) - Here's where I'm at:

So figure the volume of the room (in cubic meters or cubic feet) multiply by the number of changes per hour, and that's your flow rate: you need a fan that can move that much air per hour. Fans are normally rate as being able to move X-many Cubic Feet per Minute (CFM) of air, so look for fans that can move your amount of air.

I have worked out my inner room volume (L:4.8m x W: 2m x H: 2.3m) = 22m3. If I go for 5 room changes per hour then I need a fan that can move 22m3 x 5 room changes per hour = 110m3. With this worked out I can divide by 60 minutes (110m3 x 60 minutes) to work out how much air to be moved per minute = 1.8m3. So i need a fan that can move 1.8m3 per minute.

But that's not all! Fans only produce their rated air flow in free air, with no duct: put them in a ducted system, and the flow rate drops, depending on how much "static pressure" the system has, which basically means how much it resists the flow of air through it. So you have to calculate that, and find a fan that can move that much air at the estimated static pressure of your ducting system and room. For example, a fan might be rated at 250 CFM, but only be able to move 180 CFM with a static pressure of 0.5". So be careful there: do the math, and get the right fan. If you overload a fan with too much static pressure, it will not only not move enough air, but will be much noisier, use more power, be less efficient, and burn out sooner. Then, with all that figured out, you need to do the calculations to figure the duct size: you want the air flow speed to be less than 300 feet per second (fps) where it leaves the register. Since you already know how many cubic feet per minute you need, and how many feet per second you need, it is now simple math to find out how many square inches of cross section you need for your ducts.

This is where I'm struggling a little. Here we talk about understanding the static pressure of the system and I assumed this to mean - the resistance caused by using the fan within a ducted system, correct? However, we then talk about later working out the duct size required to achieve the relevant air flow speed, but this confuses me as I thought we had already considered duct size when working out static pressure? Sorry if I sound stupid. I guess what I am asking is: How do I work out both the required duct size and static pressure in order to choose the relevant fan size/power. What are the sequential steps to working this out? I'm thinking that one single fan will be enough for my build blowing fresh air into the studio, with just a 'stale-air-out' vent (without a fan) where stale air will be forced out. This system together with a small mini-split air con system. If this sounds ok, I assume the 'stale-air-out' vent route will not require silencers? Any help would be great. Regards Marc

I have worked out my inner room volume (L:4.8m x W: 2m x H: 2.3m) = 22m3. If I go for 5 room changes per hour then I need a fan that can move 22m3 x 5 room changes per hour = 110m3. With this worked out I can divide by 60 minutes (110m3 x 60 minutes) to work out how much air to be moved per minute = 1.8m3. So i need a fan that can move 1.8m3 per minute.

Right. But I'd go for a bit more than that. Maybe 2.5 m3/min.

Here we talk about understanding the static pressure of the system and I assumed this to mean - the resistance caused by using the fan within a ducted system, correct?

Right. It's basically the resistance offered by the entire duct system, which includes the rooms.

However, we then talk about later working out the duct size required to achieve the relevant air flow speed, but this confuses me as I thought we had already considered duct size when working out static pressure?

Size your ducts to get the correct speed for the flow rate that you need. Then based on that, check the tables to see how much static pressure drop that length of that sized duct will produce.

How do I work out both the required duct size and static pressure in order to choose the relevant fan size/power. What are the sequential steps to working this out?

As above: You figure out the dimensions of the duct (cross section) that you will need in order to get your airflow velocity slow enough while still providing the right air flow rate (volume per minute). That's what you do to size your ducts. Then you check to see what static pressure drop you will get for that size of duct, then you look for a fan that can give you the correct flow rate for that static pressure.

I'm thinking that one single fan will be enough for my build blowing fresh air into the studio, with just a 'stale-air-out' vent (without a fan) where stale air will be forced out. This system together with a small mini-split air con system. If this sounds ok, I assume the 'stale-air-out' vent route will not require silencers?

The rest is right, but you'll still need a silencer on the exhaust duct. If not, then the sound in your room will "escape" through the duct and be clearly heard outside, and in addition all sounds on the outside will be conducted back through the duct into your studio. You always need silencers on your ducts, at every place where they pass through a leaf. - Stuart -