I have a few questions based on stuff I've seen here and other places, and from discussions with other engineers, and with some architects and contractors:
1) When constructing walls with staggered studs, do the studs for both sides of the wall share common headers/footers? If so, isn't that an undesired mechanical connection between the walls?
2) I've read in a few places, that sound does not like to travel through different mediums, because of the different resonant properties of materials. I've also read that one side of a wall should be of a different thickness than the other. If that's true, when building a room where I'm more concerned with preventing sound from going out, which side of the wall - the inside or the outside - should be thicker (let's say 2 layers of 5/8"/16mm drywall on one side and 3 layers on the other) ?
That's it for now. Thanks in advance for any help on this.
-Greg
Wall construction clarifications
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WikidG
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subatom
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knightfly
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You're right that the staggered stud wall isn't as good as completely separate frames - you can improve that a few dB by using Resilient Channel under the inner wallboard layers, but it's better if you have the space to use completely separate frames. Light steel studs for those frames will give better isolation (for higher frequencies) than wood studs, because the steel studs flex more. However, for lower frequencies (the ones musicians care about but STC doesn't consider) more rigid is better.
As to directionality, there is none. If the sound is attenuated (at a particular frequency) by 60 dB one direction, it will be the same the other direction.
However, when you consider acoustics from WITHIN the room, there are choices to be made - virtually ALL rooms can benefit from bass trapping, and some of this can be gotten by using more flexible INNER wall than outer. One way of getting both good sound ISOLATION and good sound would be to use heavier, stiffer construction for the outer leaf and lighter, more flexible construction for the inner leaf. You should NEVER have more than one air space and two centers of mass (leaves) unless you have several feet of space for walls and lots more money than sense. The most efficient walls use this principle.
The main things that affect wall performance are mass of leaves, width of air space, type and amount of insulation, stiffness of frame/wall panels, dampening of panels, different inner and outer leaf resonances, and airtightness of construction. Forcing the sound to travel through different types of material also helps, due to refraction loss at layer boundaries.
Since the speed of sound in gypsum is about 22,000 feet per second and in wood it's about 12,000 feet per second, putting a layer of particle board or MDF between two layers of gypsum is a good way to further attenuate the sound. Both those materials also have good mass, which doesn't hurt either.
For a good music wall, you could do an outer leaf of two 5/8" wallboard separated by a layer of 3/4" (or even 1/2") MDF or particle board, all mounted solid and caulked with acoustic sealant, onto a 2x4 wood frame - putting kraft-faced fiberglas insulation in the stud cavities in the normal fashion will allow the fiberglas to help damp the panel somewhat. Nothing should be put on the other side of that frame. Then at least 2" of 3 pound per cubic foot mineral wool (SAFB is one term) between frames, then a steel stud frame, also insulated with normal spun fiberglas touching the inner wall panels, which should be two layers of 5/8" sheet rock/wallboard - if you mount all inner layers on Resilient Channel that's screwed to the studs, then caulk with acoustic sealant thoroughly, you should have a very good wall for music.
What you DON'T want in a wall is for both leaves to have the same resonant frequency - if that happens, that frequency will go right through with little attenuation. That's the point of the dissimilar wall construction in a nutshell.
When bedding sill plates for walls, you want just enough absorbent material to fill gaps but not enough to actually create a "spring" mount - this should be accomplished by the Resilient Channel, and only on one leaf of the wall.
Hope that helped... Steve
As to directionality, there is none. If the sound is attenuated (at a particular frequency) by 60 dB one direction, it will be the same the other direction.
However, when you consider acoustics from WITHIN the room, there are choices to be made - virtually ALL rooms can benefit from bass trapping, and some of this can be gotten by using more flexible INNER wall than outer. One way of getting both good sound ISOLATION and good sound would be to use heavier, stiffer construction for the outer leaf and lighter, more flexible construction for the inner leaf. You should NEVER have more than one air space and two centers of mass (leaves) unless you have several feet of space for walls and lots more money than sense. The most efficient walls use this principle.
The main things that affect wall performance are mass of leaves, width of air space, type and amount of insulation, stiffness of frame/wall panels, dampening of panels, different inner and outer leaf resonances, and airtightness of construction. Forcing the sound to travel through different types of material also helps, due to refraction loss at layer boundaries.
Since the speed of sound in gypsum is about 22,000 feet per second and in wood it's about 12,000 feet per second, putting a layer of particle board or MDF between two layers of gypsum is a good way to further attenuate the sound. Both those materials also have good mass, which doesn't hurt either.
For a good music wall, you could do an outer leaf of two 5/8" wallboard separated by a layer of 3/4" (or even 1/2") MDF or particle board, all mounted solid and caulked with acoustic sealant, onto a 2x4 wood frame - putting kraft-faced fiberglas insulation in the stud cavities in the normal fashion will allow the fiberglas to help damp the panel somewhat. Nothing should be put on the other side of that frame. Then at least 2" of 3 pound per cubic foot mineral wool (SAFB is one term) between frames, then a steel stud frame, also insulated with normal spun fiberglas touching the inner wall panels, which should be two layers of 5/8" sheet rock/wallboard - if you mount all inner layers on Resilient Channel that's screwed to the studs, then caulk with acoustic sealant thoroughly, you should have a very good wall for music.
What you DON'T want in a wall is for both leaves to have the same resonant frequency - if that happens, that frequency will go right through with little attenuation. That's the point of the dissimilar wall construction in a nutshell.
When bedding sill plates for walls, you want just enough absorbent material to fill gaps but not enough to actually create a "spring" mount - this should be accomplished by the Resilient Channel, and only on one leaf of the wall.
Hope that helped... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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knightfly
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If the concrete is smooth and level, you could just run beads of acoustic sealant near each edge and Ramset (.22 fasteners) the channel to the concrete.
If the concrete is rough and uneven, doing that will distort the channel. In that case, I'd use a couple layers of "Sill Seal" (pink foam stuff, designed for interface between sill plates and foundations) and only use fasteners where the high points of the concrete meet the channel. Let the acoustic sealant and Sill Seal fill in the gaps. Just be sure to caulk with more acoustic sealant as each layer is added.
If you have to "tip up" an entire wall due to previous construction, you need to improvise - in those cases you can sometimes run the bead of caulk on the bottom plate with the wall horizontal (but positioned where it's going to be) then, tip up the wall and fasten in place... Steve
If the concrete is rough and uneven, doing that will distort the channel. In that case, I'd use a couple layers of "Sill Seal" (pink foam stuff, designed for interface between sill plates and foundations) and only use fasteners where the high points of the concrete meet the channel. Let the acoustic sealant and Sill Seal fill in the gaps. Just be sure to caulk with more acoustic sealant as each layer is added.
If you have to "tip up" an entire wall due to previous construction, you need to improvise - in those cases you can sometimes run the bead of caulk on the bottom plate with the wall horizontal (but positioned where it's going to be) then, tip up the wall and fasten in place... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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WikidG
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Thanks, Steve,
Do the same rules apply for timber studs? That sounds like the method for the steel studs. I'm more concerned with lessening the low end and, since the overal STC ratings seem to be close, I'm probably gonna go with wood, since they're easier to work with (when you have to cut them - and I will) as well.
I also have a question about ceiling height and acoustics/room modes; would you rather I post it in the Acoustics section?
-Greg
Do the same rules apply for timber studs? That sounds like the method for the steel studs. I'm more concerned with lessening the low end and, since the overal STC ratings seem to be close, I'm probably gonna go with wood, since they're easier to work with (when you have to cut them - and I will) as well.
I also have a question about ceiling height and acoustics/room modes; would you rather I post it in the Acoustics section?
-Greg
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knightfly
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Yeah, sort of - if you use timber studs over concrete, you need to use Pressure Treated ones for sill plates same as normal house construction, and the Sill Seal will act as both a seal and a vapor barrier. The acoustic sealant should also be used between layers if the floor is uneven, just to make sure there is a hermetic seal. Fastening to the concrete I'd use lag shields, pre-drill holes in the plates large enough for some lee-way, then fill the hole in the plate with acoustic sealant, put a big washer on the lag bolt, and snug it down. This should all be done in one session, so the sealant is fresh when it contacts the surfaces.
Steel studs are only 20-25 gauge, and are easily cut with tin snips or aircraft snips BTW...
And yeah, if you post acoustics questions in acoustics, they'll be easier to find later. I can point you to a couple of good calculators if you're on PC and have Excel, one simple one I wrote years ago if you have Lotus, and zip/nada if you're on Mac, sorry... Steve
Steel studs are only 20-25 gauge, and are easily cut with tin snips or aircraft snips BTW...
And yeah, if you post acoustics questions in acoustics, they'll be easier to find later. I can point you to a couple of good calculators if you're on PC and have Excel, one simple one I wrote years ago if you have Lotus, and zip/nada if you're on Mac, sorry... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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WikidG
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jgreen77
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Gluing Drywall to Drywall
Gluing Drywall to Drywall
I mounted my first layer of drywall to the studs (with some MLVB in between) with regular drywall screws in a horizontal layout. I plan on mudding and taping the seams & screw heads in the regular fashion on this first drywall layer. Finishing drywall for painting can be a pain, and I need some more mass on my wall - so I am going to install a second layer of drywall in a vertical fashion over the first (this makes it easier to finish, because all of my seams will have the recessed channels).
My Question: Would anyone advise or not advise a method in which I use few or no screws to attach my 2nd drywall layer and can you recommend a process to keep the sheets as close together as possible? I have read the other posts in regards to putting holes in drywall & understand that gluing is OK, I really just want my taping & sanding the seams to be as easy as possible. I am an amateur tape & mudder - and can't afford professional help.
I mounted my first layer of drywall to the studs (with some MLVB in between) with regular drywall screws in a horizontal layout. I plan on mudding and taping the seams & screw heads in the regular fashion on this first drywall layer. Finishing drywall for painting can be a pain, and I need some more mass on my wall - so I am going to install a second layer of drywall in a vertical fashion over the first (this makes it easier to finish, because all of my seams will have the recessed channels).
My Question: Would anyone advise or not advise a method in which I use few or no screws to attach my 2nd drywall layer and can you recommend a process to keep the sheets as close together as possible? I have read the other posts in regards to putting holes in drywall & understand that gluing is OK, I really just want my taping & sanding the seams to be as easy as possible. I am an amateur tape & mudder - and can't afford professional help.
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knightfly
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Both of you need to hold up a bit; it's sounding like you've been looking at posts that were superceded with the help of people more experienced at this part of construction than me; I'm out of time for the moment, but please do NOT build til we clear this up. Thanks... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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Deluks
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This appears to be a resurrected thread but is still relevant to us 'noobs'
A few more wall construction clarifications from me...
1) When using a staggered stud wall (say, 2x4's on a 2x6 plate) How can you fit 4inch rockwool batts between your studs when the opposite stud is eating into the space between from the other side? You could compress the batts against that stud but wouldn't this couple the two wall leaves?
ie: Inside wall>rockwool>outer stud>outer wall.
2) When attaching inner ceiling joists onto top plates of a staggered stud wall, surely that top plate will transfer all energy from ceiling to outer wall. Is it possible to have a common baseplate, but separate top-plates for where space is limited. How would this best be constructed?
3) Best method for joining the baseplates of walls that are at right angles to each other? 45° mitre with glue n screw? metal brackets? end lap joint?
4) Joining the baseplates of walls that are at right angles (as above) on a 4 sided wall would mean that the baseplates wouldn't need fixing to the floor, as the 4 walls would stand up like a 'box' Is this correct?
5) Fixing wallboards (drywall, mdf etc.) to the studs. Do you attach the boards to the top and soleplates directly, or stop short of those and caulk.
Would it make sense to fix the studs slightly overhanging the top/soleplates by a few mm, and applying caulk to those top and bottoms before attaching the wallboard?
cheers
Deluks
A few more wall construction clarifications from me...
1) When using a staggered stud wall (say, 2x4's on a 2x6 plate) How can you fit 4inch rockwool batts between your studs when the opposite stud is eating into the space between from the other side? You could compress the batts against that stud but wouldn't this couple the two wall leaves?
ie: Inside wall>rockwool>outer stud>outer wall.
2) When attaching inner ceiling joists onto top plates of a staggered stud wall, surely that top plate will transfer all energy from ceiling to outer wall. Is it possible to have a common baseplate, but separate top-plates for where space is limited. How would this best be constructed?
3) Best method for joining the baseplates of walls that are at right angles to each other? 45° mitre with glue n screw? metal brackets? end lap joint?
4) Joining the baseplates of walls that are at right angles (as above) on a 4 sided wall would mean that the baseplates wouldn't need fixing to the floor, as the 4 walls would stand up like a 'box' Is this correct?
5) Fixing wallboards (drywall, mdf etc.) to the studs. Do you attach the boards to the top and soleplates directly, or stop short of those and caulk.
Would it make sense to fix the studs slightly overhanging the top/soleplates by a few mm, and applying caulk to those top and bottoms before attaching the wallboard?
cheers
Deluks
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jgreen77
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Adhering Drywall to more drywall
I have days & days before I do this - take your time and thanks again.knightfly wrote:Both of you need to hold up a bit; it's sounding like you've been looking at posts that were superceded with the help of people more experienced at this part of construction than me; I'm out of time for the moment, but please do NOT build til we clear this up. Thanks... Steve