Garden shed studio construction project - UK

Hi guys. First and foremost I am SO glad I have found this forum - I've been glued to it for about 6 hours solid. I am in the early stages of my project which I will outline the summary of below and hope to get some assistance with (what are probably quite basic) questions I have. I live in Sussex UK, and have a spacious garden in which I have built a concrete shed base in preparation for a drum rehearsal room. The shed base is not quite square (intentional) but for the purposes of my post I will talk as if it is (its close enough). Its about 6m x 3.8m (20ft x 12ft approx). The shed base is build properly on a decent sub base with a membrane etc etc and is straight on "earth" and it not connected (or anywhere near) any other building. I plan to build a room within a room most likely be: (outer) some sort of presentable cladding > OSB > DPMembrane > stud (4x2 insulated with 75mm RW3 Rockwool) > air gap > stud (same) > audio grade drywall > green glue > audio grade drywall (inner) I had planned, prior to discovering this forum, to float the floor on some dense rubber matting I have been gifted. The best way of describing these are "rubber safety tiles", the sort found in children's playgrounds. I would have then build a timber stud floor on top insulated in much the same way as the walls - however this seems highly unnecessary - based on the majority of info on here. I am a competent DIY'er and keen musician - not an engineer or studio designer so sorry if my questions seem a bit daft. 1. Without sounding daft if the outer wall is sitting on the concrete slab - and the inner wall is also sitting on the same slab (albeit separated by an air gap) does this concrete not effetely "couple" the two leaves? Should I float my inner wall on these rubber tiles I have ?? Or does having an inner wall and an outer wall (even sat on the same concrete slab) still count as a decoupled wall? 2. If I leave my concrete slab as is - is there any benefit to insulating it in any way? Or shall I literally just put some form of flooring down (most likely carpet) and if so over way - I can really lay carpet straight onto rough concrete surely? 3. If there any better use for the rubber tiles? I have them already, they are free, good mass and must be of use somewhere if not in point1. Grateful for any assistance officered. Mark - Sussex, UK EDIT: I have since found a similar post a few years old where the advice offered was to caulk down the length of the plate prior to securing it to the concrete - makes perfect sense. I am just worries (probably unnecessarily) that both the inner plate and outer plate are obviously being screwed to the same concrete slab. Clearly gravity dictates the walls have to sit on something but just making sure both inner/outer wood plate is fine to sit on the concrete slab - or should I sandwich something more than caulk between the wood and the concrete?

anyone??

Can anyone answer my question ??

Relevant to your other post re neoprene under sole plates I would suggest that you float the inner walls on neoprene to decouple the inner walls from the slab. I would also float a floor on 3 x 2s on side, 400mm OC with neoprene under. cheers john

John Sayers wrote:

Relevant to your other post re neoprene under sole plates I would suggest that you float the inner walls on neoprene to decouple the inner walls from the slab. I would also float a floor on 3 x 2s on side, 400mm OC with neoprene under.

Not preserved: floor.JPG

cheers john

Thank you very much John. I'll still need to screw the inner wall down into the slap confirm ? But use a layer neoprene between the inner plate and the slab to fill any air gaps basically because my concrete obviously isnt glass-smooth.

Any specific thickness ?

Yes, use a layer of neoprene for your inner walls. Use the stuff you mentioned for playroom floors - use a Stanley knife to cut it into 4" wide strips. You'll find the rubber mounted floor wonderful to walk on and drummers tell me their kit sounds great on it. :) cheers john

Brilliant. Neoprene under inner wall - TICK Still do screw the inner wall to the slab - TICK Make use of rubber tiles I've got (granulated rubber sort) to go under drum kit - TICK. You've been really helpful thanks.

in theory wouldnt it be better to not screw the inner wall to the slab, but leave it floting even more freely? is this more structural and safety point than acoustical issue or is the effect acustically so small that it doesnt matter? sorry for stupid questions, I'm here to learn :)

a couple of screws really doesn't matter. cheers john

John Sayers wrote:

Yes, use a layer of neoprene for your inner walls. Use the stuff you mentioned for playroom floors - use a Stanley knife to cut it into 4" wide strips. You'll find the rubber mounted floor wonderful to walk on and drummers tell me their kit sounds great on it. :) cheers john

John Sorry need to seek clarity. Float inner wall specifically on neoprene (I.e buy some) OR ok to use the rubber tiles previously discussed cut into 4in strips? Just want to be sure I understand your advice. Also - the image posted suggests the pieces of neoprene are spaced - my assumption would he a continuous strip around all four edges with not gaps beneath.

There's a 4" strip of rubber (whatever you've got) continuously under each 3 x 2 floor joist. cheers john

Been a few months off - something came up in the house and quite literally sapped my funds. However back on it now. Based on advice up this thread I now understand the limited value in even contemplating trying to float the floor. And John - based on your advice I will be recycling the rubber matting to separate the wall plates from the concrete block - accepting that they will be screwed down - so technically will short circuit" the isolation - but a limited amount - and I am benefiting from this whole studio being in the corner of a garden. The walls have to be secured somehow right??? See diagram. Thoughts gratefully received.

spesh99 wrote:

Been a few months off - something came up in the house and quite literally sapped my funds. However back on it now. Based on advice up this thread I now understand the limited value in even contemplating trying to float the floor. And John - based on your advice I will be recycling the rubber matting to separate the wall plates from the concrete block - accepting that they will be screwed down - so technically will short circuit" the isolation - but a limited amount - and I am benefiting from this whole studio being in the corner of a garden. The walls have to be secured somehow right??? See diagram. Thoughts gratefully received.

Hi, Yes bolt your sole plates for each frame down firmly into the slab. The neoprene strip is really there to compensate for any unevenness between the timber and the concrete - it fills little gaps to ensure a better air tight seal. I don't understand your simple diagram though - your outer leaf has the drywall inside the cavity but shows nothing on the outside of the studs, obviously you can't leave it open to the elements so what are you going to put there to weather proof the whole structure? Just a word of advice, it would be better to put all your mass on the outside face of the studs rather than inside the cavity, it will increase your air gap, avoid a three leaf assembly and be simpler to build. Also, make sure you fill the cavity entirely with low density fluffy fibreglass insulation. Have you figured out your roof/ceiling assembly yet? Paul

Paulus87 wrote:

spesh99 wrote:

Been a few months off - something came up in the house and quite literally sapped my funds. However back on it now. Based on advice up this thread I now understand the limited value in even contemplating trying to float the floor. And John - based on your advice I will be recycling the rubber matting to separate the wall plates from the concrete block - accepting that they will be screwed down - so technically will short circuit" the isolation - but a limited amount - and I am benefiting from this whole studio being in the corner of a garden. The walls have to be secured somehow right??? See diagram. Thoughts gratefully received.

Hi, Yes bolt your sole plates for each frame down firmly into the slab. The neoprene strip is really there to compensate for any unevenness between the timber and the concrete - it fills little gaps to ensure a better air tight seal. I don't understand your simple diagram though - your outer leaf has the drywall inside the cavity but shows nothing on the outside of the studs, obviously you can't leave it open to the elements so what are you going to put there to weather proof the whole structure? Just a word of advice, it would be better to put all your mass on the outside face of the studs rather than inside the cavity, it will increase your air gap, avoid a three leaf assembly and be simpler to build. Also, make sure you fill the cavity entirely with low density fluffy fibreglass insulation. Have you figured out your roof/ceiling assembly yet? Paul

Thanks Paul No - in truth I have not worked the roof out. Sorry the diagram is very simple it was more to illustrate the plates / neoprene and drywall. You are very right externally it wont be left like this. I will most likely (once the voids are insulated), OSB board the whole exterior, add a membrane and then cladd it a yet to be determined cut of wood. So something like (out to in) Cladding Membrane OSB Stud Wall (insulated) Drywall air gap Stud Wall (insulated) drywall GG drywall Roof i need to work out - complicated more by the fact the shed wont be perfectly square (long story and I accept complicated but doesn't really change how i build it in terms of insulation etc. Roof advice very welcome indeed.

spesh99 wrote:

Paulus87 wrote:

spesh99 wrote:

Been a few months off - something came up in the house and quite literally sapped my funds. However back on it now. Based on advice up this thread I now understand the limited value in even contemplating trying to float the floor. And John - based on your advice I will be recycling the rubber matting to separate the wall plates from the concrete block - accepting that they will be screwed down - so technically will short circuit" the isolation - but a limited amount - and I am benefiting from this whole studio being in the corner of a garden. The walls have to be secured somehow right??? See diagram. Thoughts gratefully received.

Hi, Yes bolt your sole plates for each frame down firmly into the slab. The neoprene strip is really there to compensate for any unevenness between the timber and the concrete - it fills little gaps to ensure a better air tight seal. I don't understand your simple diagram though - your outer leaf has the drywall inside the cavity but shows nothing on the outside of the studs, obviously you can't leave it open to the elements so what are you going to put there to weather proof the whole structure? Just a word of advice, it would be better to put all your mass on the outside face of the studs rather than inside the cavity, it will increase your air gap, avoid a three leaf assembly and be simpler to build. Also, make sure you fill the cavity entirely with low density fluffy fibreglass insulation. Have you figured out your roof/ceiling assembly yet? Paul

Thanks Paul No - in truth I have not worked the roof out. Sorry the diagram is very simple it was more to illustrate the plates / neoprene and drywall. You are very right externally it wont be left like this. I will most likely (once the voids are insulated), OSB board the whole exterior, add a membrane and then cladd it a yet to be determined cut of wood. So something like (out to in) Cladding Membrane OSB Stud Wall (insulated) Drywall air gap Stud Wall (insulated) drywall GG drywall Roof i need to work out - complicated more by the fact the shed wont be perfectly square (long story and I accept complicated but doesn't really change how i build it in terms of insulation etc. Roof advice very welcome indeed.

You’re creating a triple leaf system, which is not good. It should be like this: Mass - insulated air gap - mass E.g. something like this: Cladding Membrane Osb Studs Insulated air gap Studs Osb Drywall What you currently have is: Mass - air gap - mass - air gap - mass Which will lower your overall transmission loss, especially in the low end which is really where it counts. The roof and ceiling depends on a few things; firstly you should decide if you want to construct a warm roof or a cold roof. If cold roof it needs to be vented without compromising your isolation, which I can show you how to do. If warm roof then you do not need vents so it is easier to maintain isolation. It’s also more efficient. Paul

So. I have a need to build my outer wall on a single course of bricks. This is to help minimise any risk of water ingress. I have a couple of questions re your last post John if you don't mind.

Cladding Membrane Osb Studs Insulated air gap Studs Osb Drywall

Can I confirm if there is a need for any drywall on the inside of the outer wall AND/OR the outside of the inner wall (i.e the air gap). I attach an image - the points i am referring to is where the star is. Does this look right? Secondly. I still remain confused about the floor - but just float 3x2's 400mm apart on an additional piece of neoprene / rubber matting excess. What grade insulation should i place in the floor cavity? I am definitely getting myself confused about the need to float a floor or not. I am not aiming for perfection - just "good" in truth. Constrained by budget, but benefiting from the fact the whole thing is in the garden.

spesh99 wrote:

So. I have a need to build my outer wall on a single course of bricks. This is to help minimise any risk of water ingress. I have a couple of questions re your last post John if you don't mind. Cladding Membrane Osb Studs air gap Insulated air gap Studs Osb Drywall Can I confirm if there is a need for any drywall on the inside of the outer wall AND/OR the outside of the inner wall (i.e the air gap). I attach an image - the points i am referring to is where the star is. Does this look right? Secondly. I still remain confused about the floor - but just float 3x2's 400mm apart on an additional piece of neoprene / rubber matting excess. What grade insulation should i place in the floor cavity? I am definitely getting myself confused about the need to float a floor or not. I am not aiming for perfection - just "good" in truth. Constrained by budget, but benefiting from the fact the whole thing is in the garden.

No, do not put drywall in the air gap. Otherwise you will end up with: Cladding Membrane Osb Studs/air gap drywall Insulated air gap drywall Studs/air gap Osb Drywall That is a 4 leaf system... even worse than a 3 leaf system. If you need the extra isolation and therefore the extra mass then you can put extra layers of drywall (or whatever mass you like) but those extra layers must be on the same side of the studs and the existing layers i.e. leave only one large insulated air gap in the total assembly. The extra layers can also be installed in the stud bays (between the studs) pressed up right against the inside face of the existing layers, if it's easier to install e.g. on an outer leaf since you can't expose drywall to the elements. Personally, I see little point in floating a timber framed floor on top of an existing concrete slab - the slab is far more dense and damped by the earth, you are not going to beat it in terms of isolation, it is already enough. If you need to build a timber framed floor for some other reason then I would fill the voids between the joists with kiln dried sand, all the way to the top of the joists and then clad with floor grade 22mm plywood/osb. Therefore, I would not use insulation inside the floor. But speaking in general, regarding insulation inside any cavity - always use the cheap fluffy low density fibre glass, there is no need to use anything else as it will not yield a better result. If for thermal reasons you need to use something more efficient then use Rockwool inside the actual stud bays and then fill the gap between the frames with fibreglass. Paul

Thank you so much. Kiln dried sand is GENIUS! Didn't think of it at all. I think because of the height of my neighbours garden i ought to raise the floor. Its not ideal - but its safest to eliminate moisture. I have already dug a channel around my slab and filled it with gravel to help any run off from next door (naturally higher).

Paul, Could you recommend any insulation worth looking at - or literally just own brand loft stuff? I am quite surprised the more rigid board type stuff doesn't perform any better? Why is this?

spesh99 wrote:

Paul, Could you recommend any insulation worth looking at - or literally just own brand loft stuff? I am quite surprised the more rigid board type stuff doesn't perform any better? Why is this?

Is this for inside your double leaf walls/ceiling/roof? Yes the cheapest fluffy stuff you can find will be more than sufficient. The soundproofing is due to the mass layers on the wall, not the insulation - anything that can get through the mass layers (which have far more surface density than the insulation) will not magically be stopped by the low density insulation. The insulation in the cavity is to absorb the resonance of the chamber and damp the mass layers. Therefore a denser insulation is not only a waste of money but also has no benefit. Paul

John Sayers wrote:

Yes, use a layer of neoprene for your inner walls. Use the stuff you mentioned for playroom floors assurance invalidité- use a Stanley knife to cut it into 4" wide strips. You'll find the rubber mounted floor wonderful to walk on and drummers tell me their kit sounds great on it. :) cheers john

Seems like a good method to me. Anyway, thank you very much for sending us this information.