New UK Studio Build

#1

Greetings all and best wishes for the new year.

First post here for me, though I have spent many years dreamily reading posts and gazing at pictures at the late great John L Sayer’s forum and here at Suart’s wonderful forum, I’ve also enjoyed Rod Gervais’ book. Whilst there’s more information here than I could digest in a lifetime, I have tried to develop an understanding of the principles behind studio design before embarking on this project.

About me:
I have been writing, recording, playing etc for over 20 years. I currently have a mix space in our converted loft in which I can also track vocals, however in recent years this has doubled as an office and dumping ground. We moved to our current property around 9 years ago where part of the appeal was the long garden, the bottom of which I had earmarked for a studio immediately. Originally a joiner by trade, I now run a (very) small drafting and project management business. We mainly work with joinery fit out, timber facades, external windows & doors and third party certified bespoke fire door design. As a result I will be undertaking all of the design work and most of the construction, with concrete, electrical and probably HVAC (at least hook up) falling to contractors.

I have tried to outline the main requirements below, though I tend to garble, so apologies in advance:

Isolation:
I measured 45dB outside on a January Saturday afternoon, the band I’m currently in plays at around 110dB and the studio will be located 17 metres from the nearest property. If my maths is correct; the 17 metres gives me -24dB so I require an absolute minimum of -41dB from the wall construction (at the low end of the frequency spectrum!) and preferably more.

The space:
We need a space big enough to rehearse in and record a 5-6 piece rock band with some flexibility around how the space can be used. With that I have opted for one main control/live room at 33.4 square metres and a separate lobby area with some storage, access to ERV (proposed above FCL), consumer unit and to double as a vocal booth/amp locker as required at 3.3 square metres. I’m also keen to avoid entering straight into the control room from the outside.

Thermal and fire performance:
Here in the UK, legislation is such that: Building Regs kick in for an outbuilding once the floor area is over 30 square metres and planning consent is required over 2.5 metres high (in my case). Building regs call for “substantially non combustible construction” which means very little as an isolated statement, but in reality, I’m informed it means Class B or better cladding/exterior finishing and 30 minutes compartmentation with either inside or out considered as the risk side. In masonry construction this is a given and in timber frame, double drywall inside, cement board sheathing to the outer face and steel or cement composite cladding will achieve the required fire performance. Thermally; Walls must achieve 0.18 W/m2K, Floors 0.13 W/m2K and the roof 0.15 W/m2K.

Construction:
I am a bit undecided as to whether to adopt masonry or timber frame construction.

Masonry construction in the UK requires weep vents at the base of the exterior walls and above windows and doors, which obviously means the outer leaf will not be airtight, but I am unable to quantify the loss in isolation so if anyone can advise I’d be very appreciative. I am also about to engage with building control, to whom I will pose the question about fully sealed cavities (it’s my understanding the main issue is with vapour ingress from the warm side, so an internal liquid applied VCL would probably mitigate the issue). The results from Rockwool’s acoustic calculator look quite promising and I gather this would give me better low frequency isolation than timber construction given the mass of the assembly.

Proposed masonry option:

100mm block - 170 to 200mm fully filled cavity (depending on insulation spec) - 100mm block construction

Timber construction is nice and easy, very quick and slightly lower cost, however there is one large span in the design which will require structural calcs. (I use Autocad and Inventor - Inventor’s stress analysis tools are very comprehensive so I have modelled the roof assembly and it satisfies L/500 with a 2 kN/msq roof load as drawn which is more than acceptable).

Proposed timber option (outside to inside):

36mm box profile steel cladding - 50mm battens/cavity - breather membrane - 12mm cement board (around 1230Kg/m3) - 18mm OSB - 6”x2” studs @ 600 centres with Knauf Frame Therm Roll 32 between studs - 40mm gap - 4”x2” studs @ 600 centres with Knauf Omnifit slab 35 between studs - vapour barrier - 15mm plasterboard - 15mm plasterboard taped and jointed (all sheet material layers fully caulked with offset joints)

The ceiling is a bit more tricky - what I’ve shown on the attached is essentially the timber wall construction on it’s side which forms a cold roof of sorts with an added leaf below forming the inner leaf of the structure. This needs comment from the building inspector; it may be simpler to go with a standard warm roof but this will lower our FCL (I have been advised by an architect friend to try and keep the external height to 3.1m or under for planning).

Footings and slab:
Pretty standard 100mm slab atop 150mm PIR insulation. For the foundation detail; strip footing (depth TBC, we're on sand so not particularly onerous) with block courses up to DPC then either timber frame atop or continuation of the block if we go for masonry construction.

Monitoring:
I use PMC result 6 monitors at present. I would like to soffit mount these either side of the window firing downwards slightly so that they are not obscured by my small monitors which will sit on the console.

HVAC:
I’m looking at a small Mitsubishi ERV for fresh air, ducted between the rooms, servicing access will be in the lobby ceiling, and mini split(s) in the main space for heating/cooling/latent. This system is by no means fully designed and is not my forte.

Budget:
Circa £25K to get the basic structure built with HVAC based on my costings + electrical, treatment and fitout (this is based on me doing the lion's share of the construction).

—

I’ve attached my work in progress drawings based on timber frame construction. Hopefully we’re on the right track but I’d be very grateful for some advice!

Essentially:

Is the layout the best use of the space, am I even in the ballpark?

Does my downward firing soffit mounted monitor scribble look workable or is this going to cause me some wild room issues?

Some advice on which construction to adopt to best suit my requirements would be appreciated as this is a first time ground up build for me. Also of anyone can recommend an acoustic wall tie I'd be grateful; the ancon ones look great but come in at about £9.75 each which is incredibly dear for a wall tie but then again, a studio with terrible bleed would be a complete folly!

https://www.ancon.co.uk/products/wall-t ... -wall-ties

And the main question: Am I even on the right track?!?!

Many thanks for such a wonderful forum, I want to get this project right from the first pen stroke (which I’ve probably already missed!) so any advice offered will be greatly appreciated!

TH Small Studio Initial Designs.pdf: (475.75 KiB) Downloaded 191 times

TH Small Studio Initial Designs.pdf: (475.75 KiB) Downloaded 191 times

Kind Regards

Tom

#2

welcome! that is some serious engineering there...

i would run the roof support beam across the entire length for consistency. then run your i-joists. likely 195x47 @ 400mm. the roof will require enough mass to match your exterior walls - so if you cannot get the extra mass up there, then consider just framing the exterior walls.

you're on earth. lose the floating floor idea and regain that precious interior ceiling height. if you need to, create inner slabs to create more isolation, but either way, you're going to have the monolithic slab decoupled from the outside stem walls. then on the monolithic slab, create the inner foots to the slab to support the inner walls. no need for the inner stem walls. slab will have rebar in the inner footings and mesh throughout.

i'd likely go with inside-out walls internally to add absorption as built-in. then add solid and diffusive surfaces as needed.

#3

Hi Tom,

I'm surprised you found acoustic wall ties, I didn't know they existed, though I never thought to try!

@Gullfo I think he's not aiming to float the slab, this is just a fairly standard insulation under slab detail for the UK.

I don't have the head space to try to work out if your walls and ceiling will likely lead to the TL you're aiming for (not that I'm usually apt at it anyway), but to give yourself more space at the ceiling I would suggest considering lowering that internal floor even more, you may want go into tanking for more security for damp ingress though. My internal room depth is about 1.2m down from the outside to fit in two massive ceilings before breaching the UK Permitted development regs. The interesting thing at that depth is I'm pretty sure you need less insulation as the ground is not as cold, I have a very rudimentary tanking slurry diligently applied and have no damp issues anywhere that I know of.
Anyway I'm not suggesting that you go down that far but it might give you more flexibility with ceiling height and roof design, not to mention fresh air supply/exhaust silencers.

Anyway, you have begun the process well I think and just make sure you're looking after yourself mentally as it can be a strain getting it right. Lastly, budget seems a bit tight, but if you're super diligent and are able to do quite a bit of the work, then you may be able to do it. I'm a builder and studio's are just not the same, it's like having that nightmare customer who changes the spec every day you come in, shuddering progress...but you're the customer! :lol:

#4

i mention it because it looks like a layer of slab, then insulation, then slab... usually there is a barrier layer on earth, rigid insulation (if needed), then the slab... then again, if the "earth" is soft sand, then the layering shown might be needed to stablise it (my home is built on sand but it's dense, so it's just a slab on barrier).

#5

Hi, thank you for the replies.

It is indeed a no frills slab on Celotex on compacted hardcore affair. It's the most cost effective way of achieving the required U value.

@Glenn - Thank you for the advice I will opt for timber frame, it makes perfect sense now you say it; limiting factor being the roof construction isolation, why then block the walls? Laying the internal walls on the slab makes sense to me too. Whilst I like inside out walls, and have used them in the past, I'm not sure it will be an option in this instance unfortunately. I need the thickness to get the U value from the assembly and I always come back to the 30 minute compartmentation standard; I've never seen them referenced as a standard detail supported by test evidence; a question for the building inspector (for clarity, I don't see any reason why they wouldn't in practise, but as a box ticking exercise..... sorry this is my daily grind, it's ingrained).

@Purelythemusic - Lowering the floor a little is definitely an option, 1.2m though, wow! I looked into this last year but was scared off when I costed it up, the price of decent membranes! It was cheaper to apply for planning and go up. At £270 a skip now I think I worked out roughly £3.5K to get rid of soil alone if I went down 800mm. The planning fee is £322 (or something like that) so I'm hoping this will be accepted and then happy days.
Out of interest, did you do yours through building control or was it classified as exempt? I have no idea how strict building control are these days. When I did all the work on the house, it was fairly relaxed, but this was some years ago. Everything I've worked on since then has been in London and more from the fit out rather than shell and core construction side, so my perspective is a little skewed now.

I'm opting for a standard warm roof now; 150mm Celotex will get the U value and with some joist and slab jiggling I can achieve a reasonable ceiling height.

Thanks for your advice so far. I get to a point where I'm going round in circles and not really achieving anything, it's great to be able to share on a platform like this. I'm off to update my scribbles!

Cheers, Tom

#6

TomH wrote:Source of the post Out of interest, did you do yours through building control or was it classified as exempt? I have no idea how strict building control are these days.

I did have a private building control company who I had worked with before, so the guy I was used to was actually more excited about my project than most as it was unique. I think most buildings are subject to regulation and building control should be involved. Planning is another matter as you know. We had some challenges from neighbours about building our extension which included the 'outbuilding/office' on. One neighbour thought I was planning to run a commercial repair garage? Therefore I opted to limit the build height to prevent upsetting those around me, but you're right it cost me dear.

A note on building off the slab... as @Gullfo mentioned there must be mesh in the slab. I think it is recommended to have the slab designed for the weight at the perimeter of the slab, you end up with a thicker beam section of the slab around the edge and thinner a393 meshed slab through the middle, the prep could get a bit costly. I think it may then be classed as a raft foundation as mine is. You can then have outer and inner rooms fully decoupled apart from the common ground :lol:

#7

I've just been looking at your build thread, very impressive, I have room envy now. I love the way it doesn't give anything away from outside.

Been on to the building control company I'm using today who were very helpful. Annoyingly they want to see the two frames tied at the top, otherwise no issues so meeting my engineer next week to hopefully design this away. He's also going to look at the inner raft Glenn suggested, so all being well we should be in a position to issue a planning application soon.

My neighbours are pretty chilled, I mentioned it to one and he said 'i ain't bothered if you build a block of flats down there' :lol:

fingers crossed

#8

you will need to use the isolation braces to stabilise the two walls - that's pretty standard. Kinetics Noise, Mason Industries, and the ancon ones should work.

#9

Sounds like a perfect neighbour!
Hopefully the structural engineer will have a solution for it. Was it that the outer structure is not stable enough on it’s own? There would be a way to strengthen it as an independent structure I’m sure, or as Gullfo says the iso clips might be required but they’re probably planned to be standard spacing, not sure how they’ll perform as a smaller number, else you may have to use all the spec

#10

it's bracing - you would need to brace the two walls regardless and depending on any wind, seismic, or other natural impacts, will determine how much of it you need. so, for high isolation cases like room within a room, you still need the interior walls to be stable relative to the exterior ones (you don't want them tipping) so in comes isolation sway braces to solve that. the exterior walls use all the standard bracing to remain upright and attached to the foundation, and the interior walls are attached to their foundation (in this case the slab) and have isolation sway braces to ensure they're not going to tip in or out (as well as any lateral etc bracing needed for the walls and ceiling support). one of the good reasons to layer the framing with OSB or plywood, in addition for nailing, it increases the rigidity of the walls (and ceiling) and thus improve load distribution and any lateral movement.

#11

Ok I see, thanks Glenn.

I shall get a price on the Mason WIC, they have UK distribution, I know the Ancon ones are around £10 each so will see how they compare.

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