John Sayers' Recording Studio Design Forum Archive

This perhaps? We sell it at the store I work at. It's heavy and usually comes in 3x5 sheets.[/url]

Here's the data sheet for Hardibacker® by James Hardie. It comes in various sizes.

"Hardiboard" is probably an unofficial nickname for the product -- perhaps confused by its competitive cousin, WonderBoard.

--Keith

Edit 12/21/2005: Changed spec sheet link to USA version and corrected sizing information.

OK, better - the 3x5 sheets of these products (all about the same stuff) is sized for use around tubs as a tile underlayment instead of the "green board" version of gypsum, which isn't quite as moisture resistant as the duroc/hardy board stuff.

Most manufacturers also make this in full 4x8 sheets. The mass is nearly double that of gypsum, but this also makes the stuff really painful to apply unless you're Hercules - weighs about 125 pounds per 4x8 sheet.

I've not used this as part of a wall yet - I'd be a bit careful, since there would typically be only one layer so filling between sheets and getting a continuous mass might be tricky. Maybe use something like the concrete version of FixAll patch to fill in the cracks, dunno...

The other downside - expense. Gypsum is 'way cheaper per square foot. Also, don't remember seeing if the cementitious board (generic term) is rated for direct application to frames, or if it's not strong enough to provide racking resistance.

Also, you might have to fill the cracks between boards from the OUTSIDE; there should be a Tyvek liner between siding and studs, which would keep you from being able to fill cracks from the inside... Steve

knightfly wrote:. . . don't remember seeing if the cementitious board (generic term) is rated for direct application to frames, or if it's not strong enough to provide racking resistance.

Excerpt from "Sheathing Alternatives to OSB and Plywood May Be Worth Considering", published by the National Association of Home Buliders:

• Cementitious Board. Consisting of Portland cement reinforced with fiberglass mesh, this is typically used as a backboard for ceramic tile installations and has been used as exterior sheathing under a stucco cladding. Not structural in nature, buildings sheathed with cement board must have corner bracing. Producs include Durock by USG and WonderBoard by Custom Building Products.

Perhaps you'd consider Fiberboard, which according to the same article, which is structural and has "sound attenuation properties":

• Fiberboard. Known commonly as blackboard, grayboard or buffaloboard, this is constructed of wood compressed with other materials and is used primarily for wall sheathing and floor underlayment. It can be made of recycled fiber, has a higher R-value than most wood-based sheathings, has sound attenuating properties and is less expensive than other wood-based sheathings. Products include Stedi-R and Stedi-R Structural from Georgia-Pacific, Buildrite Structural Sheathing by International Buildrite, Temple Fiber Brace by Temple Inland and Celotex Premium Insulating Sheathing by Knight-Celotex.

What do you think, Steve?

Nope; fiberboard, celotex, homosote, etc, all too low mass to be a good idea. Plywood would work better, and it's still not as heavy as gypsum.

If you cant/don't wanna use corner bracing, for an outside wall structure I'd put up the heaviest plywood/OSB you can afford, put your favorite siding over it, and plan on a second inner frame with several layers of gypboard.

If people are building from scratch, it's not practical to re-invent the wheel - if you stick with proven methods, and do them right, you'll get predictable results. When you start wanting to try compressed monkey-doo, fried marshmallow, straw bales, etc, you're pretty much on your own. No one here has (or can afford) the kind of lab environment and man-hours it takes to properly test odd-ball materials.

I know we get into some pretty esoteric stuff at times, but the only time I consider that necessary is when someone is trying to "turn a sow's ear into a silk purse", so to speak; it can be very daunting (as most of us know) to convert an already existing space, one that was built with no intent or knowledge of sound isolation) into something that works. That's when it's usually necessary to get creative, NOT when you have the golden opportunity to build from scratch.

Anyway, when trying to figure out what to use (new construction) it's really very simple - for outer layers, you need structural strength and moisture resistance. Find the thickest, heaviest material you can afford that meets those requirements, and hang it on your outside frame - follow the recommendations for gap spacing (you'll be sorry if you don't) for that specific material, then caulk those gaps for a flexible, airtight seal. Cover with whatever siding you decide on, preferably one that does NOT leave gaps (like hardi-plank or other "lap" sidings). This will be your outer leaf.

For inner surfaces it's easier - in the US at least, gypsum is king. Period. Only exception I can think of is if you are a mason. People who envision wanting to hang stuff on their walls have good results putting a layer of MDF under the last layer of drywall. Put several layers on the inner frame, no seams coincident, either hire a pro drywaller who will LISTEN about decoupling or learn to do it yourself -

this

will tell you more about drywalling than you ever wanted to know, although even it is pretty light on sound construction; but you can get that here

Soooo, any-hoo, for the 4704th time, use the heaviest cheap (or cheapest heavy) stuff you can find, seal it, leave an insulated air gap (larger is better, up to 3 feet if you can afford the space) and do it again. Rather than repeat ALL this again, please re-read the REFERENCE section -

And when you're shopping for wall panels, try this - rest the panel on your foot, right where your toes curl up when you eat your favorite pizza; if it doesn't hurt, it's not HEAVY enough Steve

the reason i am talking about the hardiboard or durock is for the exterior of the building mounted straight to the studs. only thing going on top of the board would be paint. I have done this to buildings before and it looks great but will it work for a rock n roll band.

Keep it coming though. its like online college courses for free

If hardiboard or durock are continuous (no cracks, or sealed cracks with equal mass) then one layer of that should be approximately equivalent to maybe 1-1/2 thicknesses of 5/8 gypsum. One problem is the joints; this is why two layers of gypsum per leaf is the practical MINIMUM - that way, joints can be overlapped (MUST BE) for a continuous mass.

IF you can get this outer layer sealed well enough, then putting at least two layers of 5/8 wallboard (NOT celotex) on a separate frame so that the panels are at LEAST 8" apart, will give you fairly good isolation.

Rocktavian, I know you're on a tight budget, but I still think you'll be better off weatherproofing your build using 2x4 stud frames - when you consider that staggered stud walls take twice as many studs ANYWAY, you're only saving about $40 or so by framing with 2x6 caps/plates and staggered 2x4 studs, and you'll be LOSING AT LEAST 8 dB of isolation at every frequency!!

This is based on the fact that a 2x6 staggered stud wall gives 5.25" of air gap, while a double stud frame with studs 1" apart gives 8" air gap - using the exact same mass on each side, the diff between staggered 5.25" gap and separate framed 8" gap is 8 dB at 50 hZ, increasing to about 12 dB at 500 hZ and above.

All that extra noise blocking for about $40 and a 3" loss of floor space all around - keep in mind that extra space, if NONE of it is usable for music, won't help you much... Steve

I am with ya on the 2x4's. Space is precious but i see your point.The hardi board joints are basically butted end to end. would caulking them really good be sufficient?

the separate walls brings me some more questions but i will search first and see what i can find. Mainly concerned about whether the inner shell can be in contact in any way with the outer even if it is just a couple of metal strips to hold it in place. I only have have anchors set for one wall would i just ramset the inner walls?

This question has got me stumped. I had planned on using a window unit A/C and building some insulated overlapping doors on hinges to cover this thing up when the red light is on. I have no idea how that would work with 2 walls, and if they cannot be in contact at all that pretty much shoots that plan out the window.

Katrina's inflicting some serious impact on my wallet so i have nothing but time to figure out how i wanna do it. I couldnt afford to go pick the material up at $3.00 a gallon if they were giving it away.

thanks and i will search to try and find answers to some of these questions on my own. I know you guys hate repeating yourself.

rocktavian wrote:Mainly concerned about whether the inner shell can be in contact in any way with the outer even if it is just a couple of metal strips to hold it in place. I only have have anchors set for one wall would i just ramset the inner walls?

Metal strips, no. Resilient sway braces, yes. See this thread for more information on that.

This question has got me stumped. I had planned on using a window unit A/C and building some insulated overlapping doors on hinges to cover this thing up when the red light is on. I have no idea how that would work with 2 walls, and if they cannot be in contact at all that pretty much shoots that plan out the window.

See my project plan with regard to my air conditioning, ventilation, and silencers, starting here. It isn't cheap, but I'm confident it will work.

--Keith