John Sayers' Recording Studio Design Forum Archive

Hello to all and (I don't think you should EVER get sick of newcomers like myself saying) .... THANKS for such priceless information!!
Firstly, I live in South Africa and as we are about 10-12hrs ahead of you guys in the States, I will probably only be able to answer any follow up questions "the next day" if you know what I mean, so please don't think that I am being rude or disrespectful etc.
In order to keep this as short as possible (impossible actually, but I'll try), I am going to have to ommit certain details which I can obviously provide if needed.
Please keep two important issues in mind here .... firstly, I am talking about building a studio in my backyard and having limited space between my existing house and the boundary wall behind me (this space and any decisions to follow will determine the WIDTH of the studio as such).
Secondly, don't worry about building regulations as I have covered that and can literally build directly onto the boundary wall if I wish.
Also ... of CRITICAL importance is isolation, as the house directly behind mine is set back around 7ft from the boundary wall in question and the first room you hit is of course the bedroom of a very pleasant, middle-aged family man who is NEVER up late and NEVER makes a noise ... ie. a friendly guy, but will NOT take dearly to a set of oil-filled Evan's heads being pumped at 10.oopm let alone 2.00am etc!!
Now I must clarify a few issues here ... the existing boundary wall is around 6ft high and is made of what we call pre-fab here in South Africa (modular construction made of thin slats of cement which slide into slotted vertical cement posts).
There is a STRONG chance that I may have to build this wall up higher in order to "hide" my studio which will be crossing the regulation building line and this would necessitate rebuilding a complete new wall including foundations etc and this brings me to my dilemma ...... do I make a clear decision to rebuild this boundary wall using a dense block/brick in sight of it becoming my outer leaf or do I build a COMPLETELY seperate structure inside of this boundary wall.
OPTION ONE --- If I do NOT build directly onto the boundary wall as such ... I will lose crucial WIDTH space as I will need to leave sufficient gap between the boundary wall to dig the foundation for the new wall/walls PLUS I am worried about how far I will have to come away from this FREESTANDING boundary wall without compromising the isolation in any way (I would obviously want to be as close as possible in this case to regain lost space) PLUS there would be the issue of the two foundations (possibly single foundation??) and any necessary space between these foundations etc if there was to be a freestanding boundary wall.
OPTION TWO --- If I DO build directly onto this wall, my problem relates to cost AND recommendation etc.
Recommendation would pertain to getting sufficient isolation for the neighbour (I would probably leave a 30cm (12") airgap between this NEW boundary wall which would also be the outer leaf and any choice of a second floated shell/leaf, which would probably be a "triple layer" sandwhich construction of sorts allround and definately floated).
The COST factor is because, unfortunately, the boundary wall would have to be rebuilt across the entire length of the property, which is around 25 metres (about 85ft) and would be around 3.5 - 4 metres high (about 11 - 13ft) .... which is what I would have to do ANYWAY, except I could for example use UNFILLED cement blocks or any "cheaper" option for a freestanding wall as such.
This brings me to my next question ... let us say that the decision is to rebuild the boundary wall out of UNFILLED cement blocks (talking here about including this boundary wall as the outer leaf) and then ONLY FILL the cement blocks which would ultimately be assosciated with the studio as such ..... being on the same foundation, would the UNFILLED blocks compromise isolation in any way by "trapping" a certain amount of transmitted sound in the hollow centres OUTSIDE of the filled sections, but still attached by both foundation AND by obviously directly following on from the filled section (maybe I am being silly here, but any sound "trapped" inside these hollows would THEORETICALLY be "trapped" in a 2nd air gap as such.
I am going to post a second entry to this thread with a crappy picture I HACKED together (sorry ... CAD and Photoshop beyond my level of patience) incase I screw up this posting by trying to do the attachment as I am new here.
I am real sorry about the massive question, but I really didn't know how else to explain the situation properly.
Thank you for ANY help.
Regards
Steven

Here goes at my attempted jpeg posting!!

I resized your jpg down to under 800 pixels wide so no side scrolling is necessary - other than that, I'm really buried with life in general so probably won't get to your questions til tomorrow about this time, sorry; hopefully I can get caught up in the next day or two... Steve

OK, first thing - what is your local building code regarding using the property line boundary as one of your studio walls? Are you intending to pull permits for this, or try to sneak it in? Have you discussed ANY of this with your neighbors, or are you also hoping to do it without them figuring out what's going on?

If it's legal in your area to use the boundary wall for part of a building, you could conceivably use filled concrete block for the part that's containing the studio - the rest of the wall can stay hollow, no problem. Your inner leaf would reduce transmission through the concrete blocks enough not to matter one way or the other, although I'd maybe fill 3-4 holes BEYOND where the studio stops in each direction, just for the damping.

How would you accomplish a roof overhang when doing this? Keep in mind that the entire studio needs to be surrounded in every direction with a double leaf containment structure, because the weakest link will determine the performance...

Normally, a roof needs to be ventilated; as such, it's not normally a candidate for becoming one of the leaves of a mass-air-mass barrier - so some way or another, this outer mass wall would need to be continued across the top of your space (under a vented roof) and then the inner leaf would need to be decoupled from the outer one, using things like Resilient Channel, spring hangers, etc - or, if there's room you can do an inner ceiling that is framed on top of your floating floor and walls, resting the ceiling frame on the same rubber as the floor for a bit more decoupling -

Just some thoughts... Steve

Hello and thanks for that Steve.
Standard building regulations here require a 2 metre distance from boundary lines, but you can cross this line (right up to going as far as INCLUDING the boundary wall as one of the walls of your construction) if you have letters of consent signed by the respective neighbours.
I have already spoken to the neighbouirs in question and have letters of consent from them, but (although I FULLY realise the possible long term repercussions of this) ... I have NOT told them of my intentions.
They are aware that I will be using PART of the room as an OCCASSIONAL rehearsal space for my band and that I will be doing so under their scrutiny as such ... ie. I will ultimately continue to soundproof until they are happy etc.
With regards legal permits for constructing a studio, I will DEFINATELY be sneaking that one past as such .... my studio will be for my own private use (most of the time) and I would only raise all sorts of pathetic red-tape crap (trust me .... trying to get something done in South Africa is only asking for a 2 - 3 year delay whilst your applications are lost, passed on to another department, lost again, forwarded to an office of which there is no record, destroyed by fire ... and all of this whilst having to explain your COMPLICATED situation over the phone to half of the Municipalities staff every day .... none of which took English as a first language!!!).
Anyway ... my idea was to cast a reinforced concrete slab below the pitched outer roof (I don't know what you guys call this ... but the cheapest roof to put up here is a corrugated asbestos type and it comes in large sheets which requires a far LESS complicated timber structure than standard clay tiles or whatever).
I would most definately be decoupling the inner shell completely thereafter.
My main question regarding the boundary wall option was due to the fact that I was POSSIBLY going to build inside the boundary wall .... until I read a posting of yours elsewhere where it was suggested that a 2nd air gap and 3rd leaf does not necessarily have to be sealed to reduce isolation.
Thanks for the help with making up my mind and I will be posting my plans in the relevant section as soon as I have a final space allocated.
Regards
Steven

That sounds like your best way to go; however, I'd consider being a little more "upfront" with your neighbors, and explain to them that you want them to be happy with the isolation - this may get them to go easier on you than if you try to sneak something in... Steve