Photo question - your help would be appreciated

Hi there, I am planning to do my walls and ceilings exactly the same as this photo but I am unsure on a few things. If some one could comment on my questions that would be great. (1) What is put up first, the walls or the ceiling? (2)There seem to be some coloured pads at the top of the wall where it joins the ceiling, what are these? are they neopreane pads? (3)If they are rubber pads how do you seal this join when the walls are inside out like this (4) Is it important that the ceiling is mounted seperatly? My plan was to mount the ceiling joists on top of the wall frames so it would not touch the original finished gib board ceiling at all. Would this present any problems. It seems an easier construction method than trying to join joists to the original ceiling? Thanks and sorry for all the questions. I real awful that I am doing heaps of asking and basically have nothing to offer in return because I am so new to this. Thanks JohnG

The sequence and construction methods will vary depending on how much isolation you need. How critical is isolation for you? Scroll through the sticky's at the top of the forum. There are several diagrams, pictures, and ideas on which methods or techniques to use.

(1) What is put up first, the walls or the ceiling?

In my construction, I'm putting the walls up first. Decoupling them from the joists above and also sitting on a floating floor.

(4) Is it important that the ceiling is mounted seperatly? My plan was to mount the ceiling joists on top of the wall frames so it would not touch the original finished gib board ceiling at all. Would this present any problems. It seems an easier construction method than trying to join joists to the original ceiling?

What do you mean the original finished gyp board ceiling? Is this setup for a basement? you may be getting into a 3 leaf system here depending on the current/existing structure. Aaron

Thanks Aaron, I am looking for good isolation for drums, bass, gtars etc. The existing room is a single story self standing compleated structure. The existing ceiling in the room is gib board connected directly to the roof trusses. Imagine a small single level one room house. That's me. Thanks JohnG

In the photo - the ceiling goes up first. The stuff at the top of the wall is interlocking playmat cut into strips. The top of the wall is not connected to the ceiling it is psuhed up and compresses the playmat with a heavy dose of caulk. I have exactly the same construction as in the photo (with a single story free standing building with a concrete slab) - the sound isolation is incredible. Here is a similar photo showing the wall going up

Thanks Andrew, The thing I am stumped on is: How did you / do you attach the new ceiling joists to the original gib board ceiling when you start construction with the ceiling? I,m thinking that you just pull down the original gib board ceiling to expose the bottom of the roof trusses and then start the new ceiling from there but this seems a compleate waste when it is already up, sealed and plastered. Thanks JohnG

In the photo you attached - there is RC-1 channel attached to the joists and 2 layers of drywall connected to that. I've never heard of gib board - can you explain what that is for me?

Hi Andrew, Sorry, New Zealand term, Gib Board is plasterboard, Gib is the manufacturer here. So what I am saying is that the roof is already pre finised with plasterboard attached to the ceiling joists. It is an existing room in my house already compleated. I either have to rip down this plasterboard to expose the roof joists (which I do not want to do or some how attach new joists and new plasterboard to this existing plasterboard ceiling. Thanks Johng

Is there a room above that you want to isolate the sound from or is it attic space above? Personally I'd be loath to tear out the new ceiling just to add RC-1 and would be more tempted to add more layers of drywall. How tall are your ceilings? If they are tall then you could probably add a new ceiling on top of the internal walls. In this case you would have to build the walls first and then span with new joists.

Thanks Andrew, No there,s nothing above the existing ceiling, just attic/roof space. The room is 7foot high. I think I will just make the new walls slightly shorter, run a new 2x4 joist over the top, fill the cavity with insulation and then add two layers of drywall. Do you think that should do the job? JohnG

The problem will be that if the existing ceiling is only 7 ft high then you are going to end up with a very low ceiling. John / Knightfly can comment much better than me - but I think given the ceiling height I would just add more layers of drywall to the existing ceiling.

Hi John, That indeed would be a very low ceiling. What would ripping the existing plaster off leave you with?? How much room between that and the roof? It could be worth it to ripp that down (trying to save some boards) lift it up higher (attaching it to some joists that you would attach to trusses or something like that ) and then putting the inner ceiling onto the joists that your current ceiling is attached to now... does thta make any sense? :?

John, how long a span are you talking about for the new ceiling joists? 2x4's won't span a very long gap and still support themselves as well as a couple layers of gyp board, so you may run into a problem with even LESS headroom than you thought - Can you detail your roof framing exactly, including center to center distances, size of framing pieces, length that's unsupported (span), and any other details you might think of? Then maybe we can figure out a plan that will work for you... Steve

Thanks Guys, Firstly, I had a remeasure and the room/existing ceiling is actuallycloser to 8foot (2.4m) high, not 7foot. I stuffed up my initial metric to imperial conversion-sorry!! The current roof trusses are made from 2x4 at 900mm apart. They currently are covered by a 12mm plasterboard which is the existing ceiling My live room is going to be pretty small as the photo shows. I have crudly drawen the way I was planning to run the new joists on top of my new live room walls. As you can see they only need to span about 3.0m(10foot) maximum so I was thinking maybe 2x4 would be OK. It would be really nice if I could just add more plasterboard to the existing ceiling as it would mean I would have more height. but I need the isoloation as it's mainly going to be a drum room. (I was also planning to float the floor!!!) Would adding two sheets of plasterboard (10mm and 13mm) do the trick? or do I need the insulatiuon as well? How about if I got up in the roof and added the insulation to the existing ceiling? You help greatly appreciated. JohnG

First, I'm getting kind of nervous hearing all the "add some layers" talk in this case - are you SURE your trusses are 900 mm (3 feet) apart? If so, and they are really trusses, they may be fine for what they were originally intended - but each layer of gypboard will add approximately 2 pounds per square foot to the weight the trusses will be required to support. If this building was not originally intended for extra ceiling layers, you may be getting into dangerous territory by adding weight it was NOT designed for. It's really hard to say in the case of trusses vs. straight un-supported spans of single boards, because each truss is designed for its application - things like lumber species and quality, spacing of chords, type of tie plates, all add up to the total performance of the truss and can't be predicted without having the original design specs available. Normal spacing for framing members in most areas is either 16" or 24", sometimes 12" when necessary - spacings of 36" tell me the building was put up on a budget and may not be strong enough for your use without some re-design of the structure, possibly adding more framing between the existing. Any possibility of posting some actual pictures taken in your attic, so I can see what's been done? That would certainly help here... Steve

Even with 8 feet I don't think you have nearly enough space to float the floor and add a new ceiling. The room might end up very isolated but it will be too small and the acoustics will suffer. My input is that you will regret the extra expense of following your plan and end up hating the room. I think you can get some good isolation without doing any of that.

Thanks Andrew and Steve, Steve - sorry can't get into the roof without smashing a hole in the ceiling but I'll see if I can get a few shots inside and out of the building for you to picture the structure. I was thinking that if I added a new ceiling with 45mm x 90mm joist, even with only one layer of gyp board at least I could stuff the cavity with rockwool and seal the joins. The weight on the new joists won't be that great and the walls/floor will ge taking it all anyway. Most houses in New Zealand are compleatlly over engineered anway. In terms of the floor, I,m counting on the majority of the sound going down through the existing floor on piles and being soaked up by the ground about one foot beneath. That will still give me a room height of just over 7foot and fairly good isolation all sides and up which is probally the best I can do in the situation I suppose I could do like Andrew suggested and add another one layer of Gyp to the existing ceiling get into the roof and insulate the cavity above my live room but The attic space is really small and there's no man hole. I don't need 100% isolation but still want to be able to track when required. Thanks JohnG

When I suggested another layer on the ceiling I wasn't counting on the ceiling being 2x4's. It's really a good idea (as Knightfly suggested) to check the engineering loads permissable on different size studs. You don't want the ceiling to fall down and kill you. That would really suck.

No Problem, Ill see what I can do: JohnG

Span limits for US 2x4's, which are really 37mm x 90mm, when putting more than one layer of gypboard on ceiling joists - Assuming #2 and better grade Douglas Fir, using 24" centers the allowable span for 10 pound dead load is only 7 ft 3 in - for 16" centers, it goes up to 8 ft 11 in. - these spans go up to 9 ft 10 inches for 5 pound dead load with 24" centers, and 11 ft 3 in. for 16" centers - structure weight for this size framing can be estimated at 1 pound PSF, and 15mm gypboard at 2 pounds - so a double layer ceiling is just a bit over 5 pound dead load. If your timber is actually 45mm thick, you should have no problem spanning nearly 12 feet with two layers of 15mm gypboard. If those 2x4's already there are part of rated truss assemblies, you will be OK adding a second layer to the existing ceiling as well - so if you build inner wall and ceiling frames, it looks like you can get your double envelope thing happening. That only leaves floor, windows, doors... Also, when you're looking around at your floors, walls, etc, remember the mass-air-mass thing - it applies to ALL the parts of the building, including floors - we tend to discount floors since a lot of our members build in basements, and have this huge earth-backed concrete mass under them. In your case, however, if yours is on pole construction you may need to find a way to get that second mass with an air space between - Very few of us (me included) can afford to do these things twice, that's why we take the time to ask/answer all these questions... Steve

Thanks Steve, You are really a great help. It seems obveious that with my limited ceiling height I cannot afford to float the floor 75mmmm and drop the ceiling 125mm. Bearing in mind that the room is: (1) built on 1 foot poles (2) the existing ceiling is only finished with one plasterboard then attic then iron roofing (3)I want to record acoustic drums Do you think I would be better to: (1) Add another layer of Gyp to the existing ceiling, insulate the attic cavity above the existing gyp and then float the floor. (2)Leave the floor alone and "float" the new ceiling on the new walls I suppose what I am asking is if I can't do both the ceiling and the floor because of space constrants what should I, in your opinion, attempt to soundproof/seal first. My feeling is the ceiling and then if I still have a isolation problems I could atleast do something with the underside of the floor or build a small drum riser or both!! Your opinion is appreciated. JohnG

I'm still waiting to find out if your floor is just one leaf, or if there's a second center of mass (with air/insulation between them) - sound proofing is always limited by the "weak link" - if you're gonna leave the door open, why build STC 100 walls... We need to approach this as a "system" - it's all or nothing unless you just like to spend money and hurt yourself :? Do you have a way to do a basic sketch of your entire building showing everything that wasn't put there by mother nature? Until I can get a good grasp of EVERYTHING that's there, I can't say what will or won't work for you... Steve

Thanks Steve, The floor is just one leaf of particle board flooring on top of concreate piles and timber joists. The building is solid and looks well built. Heres the floor plan and side veiw of the structure you requested, Johns design for the space and my ceiling/wall plan. Thanks JohnG

More questions - will the new ceiling joists be 35 x 90, and will they be supported anywhere other than at their ends? If not, they will barely span 4 meters if placed 12" (300mm) apart, at at that would only support 1 layer of 15mm and 1 layer of 12.5mm gypsum. Is there room enough under the floor to get under there and work at all? If so, you might be able to get your second leaf without cutting down headroom - otherwise, you could use flat laid 2x lumber floated on EPDM with two layers of plywood over, filled with rockwool to cut resonance - it's likely you'll need 35mm x 140mm ceiling joists rather than the narrower ones; those would span 5 meters used on 400mm centers and be able to support two full 15mm layers of gypsum. Doing that would cut your headroom down by about 250mm total, floor and ceiling changes included. For your existing walls, that thin gypsum needs to come out if you are to kill drums and bass - you could either add a second layer of weatherboard outside (if that would work, and be sealable) or cut gypsum layers and glue/cleat/screw them against the inside surface of the outer weatherboard, then nothing on the inside of that frame and a double layer of gypsum on your inner wall. Alternatively, you could do both sides of your outer wall heavily, and NOT seal your inner splayed walls (except between the drum room and CR, of course) Can you take a picture or draw a sketch of what you call a "pile" ? I'm wondering if we're translating correctly here... Steve

This is a very interesting question about whether to do the floor or the cieling. My gut feeling is the floor because the drums are on the floor and there are other impact sounds on floors like footsteps. One thing for sure is that your wall/ceiling detail will NOT work as drawn. You are asking the gypbd to cantilever a full joist space...will not happen. Your options, depending on whether you erect the floor or ceiling first, are: