MAM optimum airspace?

Hi I finally have builders in beginning work on my new studio/drum practice/teaching room. I am pretty happy with the plans for the outer layer.. However the space is beginning to look pretty small as the new wall is built.. I want a sound proof room but "room" is gradually shrinking... I have read at some point that 12" is a good air space but anyone have any idea of what sort of difference it may make if I cut the air space down to say 8 or 10"?? When I say "air space I mean distance from my outer leaf (Brick wall with rendering on inside) and outside of inner leaf (back of plasterboard/gypsum not the stud that hold them... Any help greatly appreciated.. Thanks Geoff

Minimum you want 1" between wall frames/brick. This is the min recommended space I've seen anywheres between walls... so: Brick 1" Space 3.5" insulation in Stud Bay 2 layers 5/8" gypsum, AIR = 4.5" As you should be aware, adding more air will increase iso especially at low end. You could do: Brick 2" rockwool glued to brick 1" Space 3.5" insulation in Stud Bay 2 layers 5/8" gypsum. AIR = 7.5" If you've not already seen then check out: STC Chart link from: http://www.saecollege.de/reference_material/index.html Even if not considering Green Glue, they have done a bunch of tests, web site loaded with info: http://www.greengluecompany.com/ AND this long document from IRC (Canada) http://irc.nrc-cnrc.gc.ca/pubs/fulltext/ir761/ With all the above info (hopefully) you can then make a decision about sq ft of room verses iso of room. If it were me I would go with as little air space as possible, use green glue with 2 layers 5/8" gypsum minimum and strongly think about the rockwool glued to brick walls. You'll have a really small room anyways, acoustic wise you need to fight for every square inch. My room is bigger then yours and I am fighting hard for every square inch while trying to maintain my iso goal... Marc

thanks, The build is 13mm rendering on existing brick wall. Then air space (but filled with "pink fluffy stuff") Then studded wall with 3.5" insulation inside then 1 layer of plaster board then green glue then second layer of plaster... floor is being raised from the concrete garage floor at present to match the rest of the house ground level by DPM, polystyreen, the skreeding (not touching sides.) So if I under stand you a total gap of say 6" or 7" is a "fairly" "OK" distance?? this is edge of rendering to back of 1st layer of plaster board? I just dont want to spend all the money and find the room doesnt work because I left the gap too small... Cheers Geoff (excuse spelling)

So if I under stand you a total gap of say 6" or 7" is a "fairly" "OK" distance??

YES. Johns "inside out" walls call for less air space, like 3" or less and still work. Marc

thanks here are some pics of the work so far... Its amazing no matter how much planning you do you alway miss the most stupid things..... my first mistake... I have not had the electric box moved and now I know I can get away with a small air gap I wont be able to get to it once the inner room it constructed... DOH... Will have to get it moved.. this will mean drilling out one of the bricks the builders have just put up... :) On the wall with the various boiler pipes I intended to box them in with plaster board and render/plaster the 13mm stuff up to the edges... however I am aware that will mean triple leaf in places with plaster are... not a huge prob/area but I am wondering if there is any product I can put around the pipes that is dense to aviod the 3rd layer?? Thanks

How are you going to seal the gap between new block and existing ceiling? Marc

hi, the brick wall is a double layer.. inside build up to the current ceiling so sealed with cement the outer wall goes up past the outside of the ceiling you can see, boxing it in.. (see pic below) I am afraid I will have a few cases of triple leaf in this room but I had to do another 3 leaf for building regs... I am hoping that the fact its double brick then an inner room of double plaster with GG is sound proof enough... Do you people out there think that this might be a case where 3 leaf but more mass might be ok or am I better changing the inner room plans to "make" it only 2 leaf? Basically becuase the room itself is inside a UK house it allready has a double leaf wall all around consisting of Grey brick, air space (about3") then out side red brick... I am beefing up the inner "grey" brick wall by redering with Gyproc SoundCoat hopefully to the max 13mm (or very near.) I cant beef up the outside red brick are so I plan to build an inner room (a la attached pic) consisting of 2 layers of plaster board with Green Glue in the middle. any advice greatly appreciated. Thanks Geoff

hi, some progress pics... not much but might be helpfull if others ever convert a brick garage.. one other question to add to those above is about filling the "hole" in the wall where the pipes currently run... what is the best thing to do here?? Can I spray loads of expanding foam in there or something?? (see pic below) Cheers Geoff

Forget expanding foam; you need to fill that void with masonry or the rest of the wall is not going to help you much at all. Maybe a fairly stiff mortar mix and careful use of trowels, take it slow enough so the "plug" doesn't slump too much and make it all bulgy. Mass is your friend here as anywhere. Triple leaf isn't the best for LF isolation, but with that much mass it won't kill you nearly as much as a lighter weight m-a-m-a-m partition would. Sometimes you just gotta do what you gotta do... Steve

Those pipes'r gonna be one big flanking path, atleast build a box around it and use wool for dempening.

I am about to put an extra layer of plaster board on my existing ceiling, with green glue under... (outer leaf) I have no experience of mud and can buy non tapered board and acoustic sealant so... can I just fill the void between each board with sealant instead of mud and still have the same effect? if so what sort of gap do I leave.. minimum 1/4 inch as recommended for mud?? Also.. I know from reading other posts that "ideally" I need to use that span calculator and figure out if its safe.. but I cant make any sense of it so... I have a ceiling that has the bedroom above it.. Into the studs/joists under the bedroom floor (so in the top of my studio to be) is 1 layer of plaster board which has been skimmed... Now I planned to simply put another layer of plasterboard straight over that screwing through it into the joists/stud. BUT I just read some other posts and am worried now about if it is safe to do this? I cant see what joists are currently there without ripping into the plaster that's currently there. Its a new (last 10years) build UK house so I assume they are a standard size... do I have no real choice but to cut up and see?? Thanks Thanks Geoff

damn... I really didn't plan quite as much as I thought... next question.. Electric.. Have a main ring socket coming into the current room with one spur going off. I am planning on bringing the ring into my inner room (once constructed) to a new socket and then back out to the original socket again... (re creating the ring.) however This only gives one socket in my studio.. I intend to run 2 spurs off that socket... I don't use great a deal of power.. pc, amp for PA/Electric drum kit and some standard lamps... are there any other issues I am going to need to take into consideration?? for info this room is more of a drum practice and teaching room with occasional recording than a "recording Studio" p.s. for info the questions above.. I am pretty happy that the joists can take the extra weight of athe extra plaster boards..

You could calculate the current/load/watts of that group. Is the room the only part in the building draining current from that group? For example. Here in the netherlands one group is mostly secured to 16Amp max. That's about 3600 watts of power maximum. So a drumkit, say 300w, some light, say 500w, and some other stuff, say 1000 watts. Totally approx 2000 watts. It'll do just fine...