sand in walls

getafix · Post by **getafix** » Wed Nov 05, 2003 5:54 pm

I'm looking at building a small Listening room, i don't plan to record i just wanna keep absolutely as much sound in as possible, i have large monitors, that is 300 watt infinity with 15 drivers.
Basically my plan is in the basement with a concrete floor and wooden walls, i plan to build a room inside this straight on the concrete floor. Basically plasterboard either side of a wall inside this outershell of the basement then for inside the walls either with fibreglass wool or sand as the filler for the wall. Would the sand be better than fibreglass wool, in either a staggered stud wall or just a standard stud wall? or would i be best to staggered with wool. cause i figure if i use sand theres no point in staggered stud right?
please help would be much appreciated

knightfly · Post by **knightfly** » Wed Nov 05, 2003 9:10 pm

Sounds like you're getting things too complicated - this can cost you $$$ and effort for NOTHING under some circumstances. Here are a couple of things to read, one on basements in general and one on do's and don'ts (and why's) of sound wall construction. If you will read through my comments in the wall thread, it will explain much of the design concept of sound proofing.

http://johnlsayers.com/phpBB2/viewtopic.php?t=598

http://www.buildingscience.com/resource ... ystems.pdf

I'm running low on sleep as usual, but I'll check back after you've read some and try to clear up your questions... Steve

getafix · Post by **getafix** » Sat Nov 08, 2003 8:46 am

Ok so when i say basement i mean its under the house but its not actually underground its just a concrete slab under the house thats on like a terrace section. the walls are just wood weatherboard. So what i planned to do was build a room inside that room. Now i need to cut out the low frequencies the most and you say mass is the best way to stop that. As well as you want 2 leaves seperated by air. So would it be benifcial to have a solid wall full of sand (mass) and then theres a gap too the actual walls which would act as the second leaf but are the existing walls of the house?
Or would i be better to build the inside wall instead of being solid (filled with sand) to be staggered stud with two leaves then theres another air gap to the existing walls?
Noting its on a solid concrete slab?
thanks very much this help man

knightfly · Post by **knightfly** » Sat Nov 08, 2003 12:51 pm

Your first suggestion, depending on your existing walls, would likely end up being a triple leaf construction. Sand filled walls would act as a single leaf (one mass) but I don't have any details available on their performance. I would guess somewhere just under solid concrete. If you had a conventional framed wall inside that, then there would be an air space between the sand filled wall and the outer sheathing, then an air space where the studs are, then another mass (inner paneling on the stud frame) - this = triple leaf construction, and will actually have LESS isolation than if you removed the outer panels on the stud frame (gives a wider air gap, so better Transmission Loss)

I need to know EXACTLY how your existing walls are built, layer by layer, outside to inside, then I can suggest best ways for the isolation you need. Also, what about ceiling? Do you also need to isolate your room from the upper floors? If so, you also need to describe the ceiling construction (looking from down below) step by step like the walls - no detail is too small, it all works together or it doesn't work at all... Steve

getafix · Post by **getafix** » Sat Nov 08, 2003 1:12 pm

The walls and roof, which i do need to isolate from, are just single layer weather board like i guess inch thick wood with 2x4 studs. Thats it only wood on the ouside of the house and nothing on the inside, completely uninsulated.
The floor/cieling is the same with underlay and carpet on the upstairs side of it. with 2x4 joists.
The two options i gave were a one of the other. I was planning on EITHER the double leaf wall with the staggered studs. So two air gaps eg the staggered stud and then the gap between the second leaf and the sheath of the house. OR the solid wall of sand then the air gap would be between this sand wall and outside "sheath" ie the weathboard on the outside of the house.
cheers
mike

knightfly · Post by **knightfly** » Sat Nov 08, 2003 2:08 pm

Cool, Mike, in this situation having nothing on the inside of your studs is a GOOD thing. Saves having to take it off...

I'm out of time for now, just a few questions - you said "The floor/cieling is the same with underlay and carpet on the upstairs side of it. with 2x4 joists." - REALLY? 2x4's? How far apart are they, and what's holding them up? Talk to me like you're building this place piece by piece... Steve

getafix · Post by **getafix** » Sat Nov 08, 2003 3:26 pm

well the rooms only 3 meters wide so teh 2x4's just span from the wall on hte left across to the wall on the right and theres like a conservatory above it. The 2x4s are about 35 cms apart. Theres no vertical supports aside from the two walls its quite a small space about 3 meters wide by about 4-5 meters long depending on how long i decide to take the it but yeha
and i need to cut a decent amount of sound out from going up into the conservatory i was looking at that technique on the sae site with two pieces.
i hope thats what you need. The floor under me is solid concrete block theough.
cheers
mike

knightfly · Post by **knightfly** » Sat Nov 08, 2003 5:44 pm

I just checked span for 2x4's as floor joists, and at those spacings they are only rated at about 2 meters. The problem is that I don't want to suggest something to you that will cause damage or get anyone hurt, and right now I wouldn't recommend adding ANYTHING to your ceiling.

I know I'm sounding picky here, but I really need to know for sure that those really are only 2x4's - if they are, then more structural changes will need to be done than just adding to what's already there... Steve

getafix · Post by **getafix** » Sun Nov 09, 2003 8:27 am

I wasn't gunna attach the cieling of te room to the existing roof. i was just gunna put it on top of the walls i make, but yeah the room upstairs moves a bit but its been sweet for years and years, but i think someone mentinoed a retaining wall going in sometimein hte next few weeks but i'm not sure if that will make it any better

knightfly · Post by **knightfly** » Sun Nov 09, 2003 11:17 am

You're right, under the circumstances resting your new ceiling on new walls would be much safer. Is there enough headroom for 2x6's below the existing ceiling? that would let you do a good tight ceiling, and with independent inner walls you'd have a pretty tight envelope, should be able to make it really quiet... Steve

getafix · Post by **getafix** » Mon Nov 10, 2003 3:30 pm

hmmmm might be pretty damn tight to fit i dunno prolly have just go with 2x4s but we'll see.
But yeha so you reackon the solid sand walls or insulated walls? in this situation. thanks for your help with this i had a done decent amount of reading figureing shit out but just need to put exactly what i was doing to someone and see what they said.
cheers man
mike

knightfly · Post by **knightfly** » Tue Nov 11, 2003 3:44 am

Mike, please don't put 2x4's up there and try to hang enough wallboard to make it soundproof - there are REASONS for span tables, and they allow for no more than 7 feet 3 inches with 2x4's on 24" centers if you're going to have 2-3 layers of drywall on them. This increases to a span of 8' ll" for 2x4's on 16" centers, but this will reduce sound isolation by 2-3 dB and STILL doesn't span your room.

If you ignore these recommendations, you're asking for problems and pain.

As far as walls go, in your case I'd think about fitting Tyvek house wrap into your stud cavities, then adding at least one layer of 5/8 gypsum wallboard in between each pair of studs firmly against the inside of the outer wall board - then insulation, then the new wall frame with a layer of 5/8 wallboard on the INSIDE of the frame, and a layer of 1/2" wallboard over that. See this thread for more info on wall construction -

http://johnlsayers.com/phpBB2/viewtopic.php?t=598

I would NEVER try to fill existing non-concrete walls with sand - even though it would give almost as good a mass as concrete, it will settle and exert so much pressure on the lower sections of wall that the chances of the wall NOT falling apart would be very slim... Steve

getafix · Post by **getafix** » Tue Nov 11, 2003 9:13 pm

well the decision has been made i rang the sand company today and sourced weight and prices and well, for the long walls of 1.7 meter high by 3.5 long, 40 cm gaps between studs the wall was gunna end up weighing 6.5 tons
heh and they charge $300 per ton for sand so pardon my french when i say fuck that.
I sized up the room measured properly the roof studs are in fact 3x5s the existing ones that is
the room once built giving a ten centrimeter gap between teh stud of the existing wall and the outside of the stud of the to be built wall. The room will be from the inside wall to the otehr inside wall 2.3 meters wide and 3.5 long
i figured i would build the roof in two parts so two 2.3 by 1.75 meter pieces and slide them along the top of the walls. So it would be more beneficial to leave teh outside of the to be built walls with no plasterboard rather than having a double leaf wall with staggered stud then the 10 cm gap to existing wall
thanks for your help man, this is the most help i've ever had from any forum
chhers
mike

knightfly · Post by **knightfly** » Tue Nov 11, 2003 10:50 pm

You're welcome - I'm not sure if I understand what is going where, though - you do understand that the TOTAL construction, both old and new, should have only two places from outside to inside where there is any solid mass? And that each mass can be multiple layers but with no air space between layers? I've included some examples just to make sure you are on the right track.

The same idea goes for ceilings too - any design that doesn't follow the basic principle of two masses, one air space, is NOT as good isolation... Steve

getafix · Post by **getafix** » Wed Nov 12, 2003 6:16 am

ok so the two options are a and take e but put a ten centirmeter gap from the middle wall to that extra outside single leaf wall.
So say the the shell of the house acts completly independent of the new to be built room demonstrated in e the bottom half of that diagram already exists, now i was thinking take a 10 centiemter gap inside that and THEN build teh top half of it ie the double leaf staggered stud?
cheers
mike