Ceiling for new rehearsal studio

Hi all I am based in London, England and am currently working on the build for a live room & control room housed within a 700sqft unit (see configuration below). Looking for some expert advice regarding the ceiling construction for a new rehearsal studio I'm building. The live room (5.5m x 4m) will be built as a 'room in a room' with a 8" air-gap between the perimeter wall (made of breeze block/cinder block). The walls be constructed out of single ply 19mm OSB/2x4 Stud frame/100mm Mineral wool filler/15mm drywall/acoustic membrane/15mm drywall. This will then be treated internally for acoustics. This room will be completely independent of the control room and existing unit. My concern is not with the sound going through the walls as I believe the mass-air-mass will suffice in this configuration however I need some advice regarding the ceiling construction for this build. The current roof is plastic corrugated with little to no reducing qualities. This roof spans the entire length and width of the unit so a solid ceiling will have to be constructed to greatly reduce the noise going out through the top. I am thinking the following for the ceiling composition that will be mounted under the new joists: - OSB single ply - joists filled with 100mm mineral wool - resilient channels - 2 x 12.5mm acoustic plasterboard with acoustic membrane filler between layers fixed to the rc's. - internally, clouds, bass traps and possibly carpet tiles fixed to the ceiling. The type of music will range from loud rock to electronic (low bass frequencies) Will this configuration suffice? All opinions & criticism welcomed. Thanks Val

Hi Val. welcome! Please check the forum rules, for something you forgot... :) Regarding your question: Isolating a room is an "all or nothing" proposition. The overall isolation is only as good as the WEAKEST part, so if you go with that much lower level construction on the ceiling, then you wasted a lot of money on the walls! In other words, the ceiling needs to isolated to the same level as the walls. Also, 12mm drywall is not a good isolator anyway, acoustically: Too thin, too flexible, resonant frequency too high, not enough mass, etc. It would be much better to only use 15mm, or even 16mm (or more!) if you can get it, throughout the entire build.

15mm drywall/acoustic membrane/15mm drywall.

What do you mean by "acoustic membrane"? Are you talking about some form of MLV? If so, then forget it: our marketing hype. Mass is mass, and the sound waves don't care how much you paid for the mass. All they do is react to the mass. MLV is rather expensive mass, and wil give you no benefits when sandwiched in a wall like that: contrary to popular belief, it is not, and does not act like, constrained layer damping. On the other hand, if you are talking about REAL constrained layer damping, such as Green Glue, then go for it! That stuff really does work. Anyway, back to the ceiling: If you go with your suggested construction of corrugated plastic / un-damped air gap / OSB / damped air gap / drywall, then you have a three leaf system, in theory. However, the corrugated plastic is most likely rather light weight, and if you can get a good distance between it and your OSB (in other words, a very large air gap) then you should be OK. However, I'm not sure I understand the construction you are proposing: Are you saying that you will attach OSB to the underside of the existing rafters / joists (which have the corrugated plastic on top), then attach more joists to the OSB, then attach RC to that, then attach the drywall to the RC? If so, I'm not sure that will work, or even be safe. You would have to check with a structural engineer to make sure that the existing structure can safely handle all that extra load. On the other hand, if you are saying that you plan to span new joists across the new inner-leaf wall, with the OSB on top and the RC / drywall underneath, then you have a flanking problem from the inner leaf walls to the OSB, so that won't work. Maybe you could prepare a SketchUp model of what you have in mind, and post it here. It's hard to imagine exactly what you have in mind without seeing it in detail.

Will this configuration suffice?

That depends! How much isolation do you need? (In real numbers: how many dB of TL do you need here?). You say you have a full rock band inside, so we are talking upwards of 115 dB in there, so how quiet does it need to be outside? - Stuart -

Hi Stuart Many thanks for for feedback. Was it the lack of dimensions or was the picture too big!? Please enlighten me re my oversights and of course, apologies... I will take on-board your advice regarding the green glue. I was indeed referring to mlv but if you believe that is not effective in both cost and performance than GG I'll take it out of the mix. Are there any other green glue alternatives in the event I cannot source this easily in the UK? The location of the unit is on a disused urban farm.No animals, just buildings. The unit I'll be using is in the middle of 6 similar ones used by various trades (mechanic/builder & storage/furniture maker and empty ones) so noise should not be an issue for them - most of our playing will be after working hours (9am-5pm) during the week. There is a house thats located approximately 50m away from the unit. The mass of the control room should block any sounds that head in that direction. In between the unit there is a 6ft path, another 2 story out-house, some land, a bunch of 20m high evergreen trees then a garden then the house so there should be enough barriers to diffuse any sounds moving towards the house. In the other direction, there are just fields before you get to London-Heathrow airport that's noisier than anything within 10 miles of where we'll be! Walls: I have managed to source around 40 lots of 2400mm x 1000mm x 19mm for free so want to make use of these as best I can. See proposed configuration below: This will be the config for all 4 walls (minus doors). These walls will then be treated acoustically afterwards. Ceiling: The joists on the current roof are just holding up the plastic/sheet roofing and will not come into contact with the new roof/ceiling construction I propose. There will probably be a 8-10" gap between the existing joist and the top of my roof. Ive been chatting with a structural engineer who advises that the load on a the ceiling joists at the proposed mass will suffice - 2 ply 15mm drywall equates to 4lb per sqft - the model I am using will hold a potential 10lb per sqft. The central joists (longer ones) will be braced every 1.5m I'll be uploading some pictures to clarify what Ive tried to explain through my diagrams. Will get a Sketchup of what I think it will look like too, over the weekend. Thanks again and look forward to your comments. Regards Val

Hi Val,

Was it the lack of dimensions or was the picture too big!? Please enlighten me re my oversights and of course, apologies...

viewtopic.php?t=3231 It's the part in big blue letters, about one third of the way down the page... :)

I will take on-board your advice regarding the green glue. I was indeed referring to mlv but if you believe that is not effective in both cost and performance than GG I'll take it out of the mix.

It's not that MLV doesn't work to isolate sound: it DOES work, but only because it is mass. The problem is that it is EXPENSIVE mass! You would get more benefits, much cheaper, from adding a third layer of drywall instead of the MLV. MLV dos have some uses in isolation (such as for example where you need very flexible mass to get around some strange shaped object, like pipes, for example), but it has no magical properties, despite what some manufacturers want you to believe. Mass is mass, Sound waves don't care how it got there, or what the number on the price tag said. All they care about is the mass (and hte density, to a certain extent).

Are there any other green glue alternatives in the event I cannot source this easily in the UK?

I do recall seeing build threads here from other folks in the UK who managed to find it, I think. There is also an Australian version that John says works fine too, called Quiet Glue, or something like that.

in the middle of 6 similar ones used by various trades (mechanic/builder & storage/furniture maker and empty ones) so noise should not be an issue for them

OK; but ow about THEIR noise being an issue for YOU??? Mechanic / builder / carpentry shop all suggest "Noise" to me, with a capital "N"! So does the word "Heathrow" :shock: Are you close to one of the approach paths, or departure paths? Can you hear the jets as they take off and land?

There is a house thats located approximately 50m away from the unit. The mass of the control room should block any sounds that head in that direction.

Low frequency sound (the most difficult to isolate. Think: drums, bass, etc.) is not directional, and once it is out of the building, spreads out evenly in all directions. There is no "this way" or "that way" for low frequency sound. But you do seem to have some things in between and a decent distance, so that should not be too much of an issue.

40 lots of 2400mm x 1000mm x 19mm

OK, but WHAT? "2400mm x 1000mm x 19mm" could be wood, metal, rockwool, fiberglass, ... ?

See proposed configuration below:

You are building a three-leaf system there! Bad. You only ever want two leaves in an isolation wall, not three, four, or any other number. Drop the OSB on the outside of the studs, or move it to the inside (under the drywall) and you will improve your isolation greatly! The wall is a resonant system, and you want the frequency as low as possible. Putting multiple leaves in it raises the frequency. Two leaf, and only two, and nothing but the two... Same for your roof: If your engineer says the existing structure can handle it, then I would move the OSB up the bottom of the existing joists, to complete the outer shell, and I'd add another layer to it, to add mass (maybe drywall). THEN eave your 8" air gap, and build the inner leaf as you show, the same as for the walls. Yes, you will still have three leaves on the roof, but the third leaf there (corrugated plastic) is very low mass compared to the other two, and the gaps are quite large. The only issue with doing it this way, is ventilation.... that plastic probably needs to be vented some way, to prevent moisture buildup, and the associated problems. Talk to a builder to see how to deal with that. You probably have to vent the space between the new OSB and the corrugated plastic, and you will most likely need a vapor barrier up there somewhere. The builder can tell you how and where. Apart from that the basic plan looks fine. - Stuart -

Hi Stuart Thanks for the feedback. Regarding the surrounding noise, Im not worried about this emanating from the people around me. The builder just uses his unit to store materials & tools. Much the same for the carpenter. The mechanic is two units away from me. I'll be like rehearsing/recording after 6pm most evenings and weekends so should work out fine. The flight path for Heathrow varies. The unit is about a 3 miles away from the main terminal block though the runway is slightly closer. Saying that I have been at the unit several times before I took it on, at various times of the day, and the flights taking off did not distract from regular conversations outside so I believe it will be OK inside. In fact I was there for 5 hours today and not a single plane was heard overhead. Sorry, I should have added OSB to the 2400mm x 1000mm x 19mm - this the free stuff thats knocking around. Here are some pictures of the unit to give you an idea of my challenge regarding the roof. As you can see, there is one central joist that spans the length of the unit (30ft) with one other central joist perpendicular at roughly halfway down. The remainder of the roof is supported by smaller joists. The lights will of course be removed though attaching the OSB to these existing joists will be difficult as they are at different heights. The piece of 2x4 in the corner is the height I would like for the top of the new roof with the ceiling hanging about 6-8" lower, which will comprise of the materials suggested previously with the change of the OSB included in the mass of the ceiling rather than on top of the new joist giving the unwanted third leaf. Regards Val

Hi Stuart Thanks for the feedback. Regarding the surrounding noise, Im not worried about this emanating from the people around me. The builder just uses his unit to store materials & tools. Much the same for the carpenter. The mechanic is two units away from me. I'll be like rehearsing/recording after 6pm most evenings and weekends so should work out fine. The flight path for Heathrow varies. The unit is about a 3 miles away from the main terminal block though the runway is slightly closer. Saying that I have been at the unit several times before I took it on, at various times of the day, and the flights taking off did not distract from regular conversations outside so I believe it will be OK inside. In fact I was there for 5 hours today and not a single plane was heard overhead. Sorry, I should have added OSB to the 2400mm x 1000mm x 19mm - this the free stuff thats knocking around. Here are some pictures of the unit to give you an idea of my challenge regarding the roof. As you can see, there is one central joist that spans the length of the unit (30ft) with one other central joist perpendicular at roughly halfway down. The remainder of the roof is supported by smaller joists. The lights will of course be removed though attaching the OSB to these existing joists will be difficult as they are at different heights. The piece of 2x4 in the corner is the height I would like for the top of the new roof with the ceiling hanging about 6-8" lower, which will comprise of the materials suggested previously with the change of the OSB included in the mass of the ceiling rather than on top of the new joist giving the unwanted third leaf. Regards Val

Hey Val, this is where I bought the Green Glue in the UK - http://www.greenglue.co.uk/ (it's a division of RPG Europe)

Thank you TFV - much appreaciated! :) May I ask what setup you have? Can you tell how much of a difference the green glue made? Val