double vapor barrier

[DAX616]

For sound isolation purpouses I have heard using a double wall. In a basement, wouldn't that constitute a double vapor barrier where mold can grow etc. etc.If any body has a construction background or knows the proper way to construct a double wall with out introducing a double vapor barrier please let me know.

Dax

[picky]

DAX616: I recently built a theater in my home's basement in Michigan, where things get mighty damp during the summer. I would not recommend building a double-wall along your basement's concrete or cinderblock outside walls as I believe there would be little (if any) benefit. I recommend a standard wall with no vapor barrier (so things can breathe) and rigid, mineral fiber insulation. Top that with a layer of 1/2" Homasote sound-deadening board (available at Home Depot and Lowes), topped with a sheet of 1/2" or 5/8" drywall. If you need additional sound damping then add a sheet of sound block membrane to the studs before installing the Homasote and drywall.

However, if you are building an interior basement wall, then I do recommend the double wall approach, as trapping moisture should not be an issue. Stagger the studs of each side so they do not touch. Thread a sheet of sound block membrane in between all of the studs from end-to-end. Install rigid, mineral fiber insullation to each side of the wall. Top that of with a layer one each side of your wall of of 1/2" Homasote sound-deadening board, topped with a sheet of 1/2" or 5/8" drywall. I built such a wall between my theater and my furnace/laundry room and I cannot hear the equipment running on the other side of the wall while I am watching movies.

[DAX616]

The rigid mineral fiberboard you mentioned, is that the dark colored board usually seen on th outside of the house before siding? How does the sound board @ lowes compare to somthing you would order from an accoustic place like Auralex? Thanks for your reply

Dax

[picky]

DAX: The mineral fiber insullation is yellow-ish, not black, and it would not be place on the "outside" of a building. It is very dense and it goes between the studs in place of the "Pink Stuff". Funny you should mention "Auralex" as they carry this type of insullation, but you may find it at a builder's supply for less. A picture of the mineral fiber is shown here:

As far as the Homasote sound-deadening board, this should not be confused with sound blocking membrane such as Auralex sells. They are two different animals:

Homasote sound deadening board is a light gray-colored, fiberous board sold in 4'x8' sheets and made from what appears to be highly-compressed paper products. In the old days we used to call it "train board" and mounted our Lionel and HO model train layouts on it because it deadened the noise a bit, and it is far-cheaper than plywood.

Sound Block Membrane is a black (usually), VERY dense (and heavy), quite expensive rolled rubber-based membrane that when used correctly, can help block sound. It comes in many thicknesses. It must cover all of the studs and form an air-tight cover over the entire wall frame, otherwise, sound and/or noise will find its way through. A picture of sheet block is shown here:

DO NOT confuse this stuff with roofing felt. They are completely different!

[dkp]

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On 6/4/2004 6:09:44 AM picky wrote:

DAX616:

I recently built a theater in my home's basement in Michigan, where things get mighty damp during the summer. I would not recommend building a double-wall along your basement's concrete or cinderblock outside walls as I believe there would be little (if any) benefit. I recommend a standard wall with no vapor barrier (so things can breathe) and rigid, mineral fiber insulation. Top that with a layer of 1/2" Homasote sound-deadening board (available at Home Depot and Lowes), topped with a sheet of 1/2" or 5/8" drywall. If you need additional sound damping then add a sheet of sound block membrane to the studs before installing the Homasote and drywall.

However, if you are building an

interior basement wall, then I do recommend the double wall approach, as trapping moisture should not be an issue

. Stagger the studs of each side so they do not touch. Thread a sheet of sound block membrane in between all of the studs from end-to-end. Install rigid, mineral fiber insullation to each side of the wall. Top that of with a layer one each side of your wall of of 1/2" Homasote sound-deadening board, topped with a sheet of 1/2" or 5/8" drywall. I built such a wall between my theater and my furnace/laundry room and I cannot hear the equipment running on the other side of the wall while I am watching movies.

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Picky-I'm just kind of thinking out loud here, but I believe that you would get a small amount of moisture that comes from the basement floor, as well as the walls. Granted, this would be a much, much smaller amount than that of the walls, but my question would be whether that amount would be significant enough to cause a problem.

We currently have an unfinished basement that I plan to relocate my theater to this fall/winter and am looking at the sound barrier issue myself. Thank you for the input...

David

[michael hurd]

Any moisture is detrimental, as the studs for the walls that sit on the concrete floor will slowly rot and create mold. I would recommend adding a layer of DRI-core ( a combination moisture barrier and low-profile subfloor system ) before building any interior walls.

The stud walls would be built on top of the dri-core floor, leaving a 1/4 inch space from all exterior walls for ventilation and expansion / contraction. The design of the panels permits air movement underneath, and allows moisture to dissipate.

One added benefit of the dri-core system, is that it increases the r-value ( r2 ) and has the effect of warming a room by 6-7 degrees.

For the walls, superseal dimpled membrane will allow the walls to breathe as well, and any moisture to evaporate. It can also be used on the floor, but I feel the dri-core system is an easier solution.

When applying the membrane to the walls, ensure that you have enough length to reach a 1/4" off the floor, again for moisture drainage and breathing.

You can read more about these materials at www.dricore.com, and at http://superseal.ca/dimpledmembrane.html

[picky]

All: Good points about moisture of any type for basement floors and walls.

dkp: Initally we were talking just about walls, so I didn't mention the floors. Good point!

The "local building experts" here in Michigan recommend using a pressure-treated wood (such as Wolmanized 2x4 or 2x6) as your wall's sole plate. They recommend against any kind of vapor barrier or plastic on basement floors or walls so they may breathe. They also do not recommend kraft-faced insulation in basement walls. For non-theater applications they would even suspend with the use of studs all together and they say you should anchor 3/4" furring strips (at 16") intervals to the basement walls and install Styrofoam sheet insulation in between the strips and then drywall over them.

Prior to construction my walls, I repaired any cracks with mortar or hydraulic cement and then I coated the cinderblock with two thick coats of DryLoc waterbarrier paint. Then, I built the 2x4 walls using a pressure-treated sole plate that I shot powder anchors through and into the concrete floor. I nailed a second, non-pressure-treated 2x4 on top on that and built the walls, anchoring them on top to the floor joists above. At no point do my constructed walls touch the outer cinderblock wall. This allows the air to move behind the walls.

If you do not use the sound block membrane in the outer walls, there will be no moisture barrier and the walls should be able to breathe. But, that changes if you have to have the sound-blocking potential of the sound block membrane in the outer walls. None of this moisture barrier concern should matter on an interior basement wall where both sides are exposed. But you still need to use pressure-treated lumber for the sole plate.

Any wood used anywhere in a basement that will touch the floor, should always be pressure-treated! Pressure-treated wood should always be cut out-of-doors, not in your basement and while you are wearing a mask. Never burn the scraps in a camp fire. They can be toxic.

[michael hurd]

Picky - the products that I mention have a plastic barrier which has raised bumps, which contact the floor surface, so that there is a space between the cement and the actual floor surface.

The product kind of looks like an egg carton, albeit much smaller. The bumps protrude 8mm ( 5/16" ) from the top surface. If this type of product is not used, interior walls should have a vapor barrier between the cement and the bottom plate of the stud walls.

[picky]

Mike: Yes! I have seen that stuff. It just recently came out and I believe it's a great idea. It doesn't apply to what I was saying, as I was talking about only solid plastic sheeting. Your stuff should be great to use, I only wish they'd have made it BEFORE I started my basement project! Figures, doesn't it?

[michael hurd]

Well, new products hit the market all the time, and it is hard to keep up with the latest and greatest.

[Champagne taste beer budget]

How would having in-floor heat effect the amount of moisture that you'd see? They came in yesterday and sprayed the rubberized waterproofing stuff on the outside of the poured walls for the downstairs, it is a walkout so two walls will be against dirt and the other two will be open to the air outside with doors and windows, southern and western exposure open. Supposed to be putting up the outer insulation and drain pipes inside and outside on monday, then backfilling, then hopefully start seeing some wood go up! Should I be concerned with direct wall or floor contact with this set up? Thanks.

[artto]

Both Picky & Mike are correct. Basically it boils down to your particular situation (what kind & how much of a moisture problem you have) and local building codes. In any case, you want the walls & floor to be able to 'breath'. Using a double wall against an outside foundation wall will have little or no impact on sound isolation.

In my situation, I used mineral rock wool between the studs. 1/2" Celotex (similar to Homosote) sheathing over the studs, except in the corners where the Khorns are, where I used solid core 1/2" marine grade plywood. 5/8" Gypsum 'sheetrock' over the Celotex.

Since I'm using Khorns, I wanted the rigidity of the concrete floor. I first put a layer of linoleum tile on the floor, carpet padding & heavy carpet over that.

My lower level is not a 'full depth basement', and we're on relatively 'high ground' that is well drained, so I don't have much of moisture problem to begin with (knock on wood, hehe).

And yes, having some sort of radiant in floor heat helps greatly. If you can do this, by all means do it! You shouldn't have any problems with direct wall or floor contact provided you have adequate drainage around the foundation & under the floor.

[Champagne taste beer budget]

Good to hear, I didn't need any more considerations thrown into the mix for finishing the downstairs, which would include the listening room. Yes, the Wersbo (sp?) in floor is already a given for the downstairs, and have drain tiles going in both outside the foundation footings and inside, under the poured floor.

[Klipschfoot]

I won't repeat my previous posts regarding soundproofing, but I just want to reinforce that it is better to make sure that there are NO water/moisture issues before you remodel your basement. Sound absorption is easy. Moisture barriers can be difficult.

On vapor barriers, make your vapor barrier between the studs and wall first. Then put up a plumbed wall that is not necessarily flat against your basement's foundation walls. The goal is plumbed, straight, dry walls.

For outside, consider french drains if there is any potential moisture problem. Eliminating moisture will also be a deterrant to termites, which can thrive on moist wood.

[dkp]

There are so many things to consider. At times, I am overwhelmed by the amount of information needed to make a good decision regarding equipment purchases, room layout and design, etc. No wonder those lil Bose cubes are so popular!!!! One purchase and done...or not!

Anyway, we are in the process of designing a basement theater and dealing with a number of issues-one being the vapor barrier/water issue. I will start a new post when I get a bit more time, but thanks to all for donating your time and knowledge to this forum. It is well appreciated and very helpful.

David

[formica]

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On 6/4/2004 8:26:22 PM Klipschfoot wrote:

I just want to reinforce that it is better to make sure that there are NO water/moisture issues before you remodel your basement. Sound absorption is easy. Moisture barriers can be difficult.

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I fully agree... This thread seems to touch several unrelated points that go into designing and building a home.

- Soundproofing basement walls: Picky brought up a good question on his first post... are these interior or exterior walls?

- If these are exterior walls... how close is your neighbour? You have air bound and structure bound sound transmission (similar to impact transmission). Given the mass of the foundation and of the soil... I don't think air bound sound transmission is a problem with an exterior neighbour. To get structure bound transmission, you'd need to vibrate the actual foundation (by bolting your speakers to the wall for example... ). The heavier the walls, the less the low frequency transmission will be.

- Interior walls/ceilings are where most people concentrate their efforts to reduce annoyances to other home users, and reduce ambient noise. There are plenty of good recommendations here... as well as peppered throughout this forum. I just like to emphasize the importance of having an air tight seal... as air bound sound has a tendency of finding it's way through the smallest of holes.

- Waterproofing: I don't think this was the initial question, but depending on settlement, membrane durability, water drainage, and the water table... many basements develop water infiltration problems during their lifetime. Most standard one-part asphalt coatings are "damp proofing" and are not intended as waterproofing. On the exterior, elastomeric membranes perform better but are substantially more expensive. On the interior, I agree that leaving an air gap between your finish false wall and the foundation. Thermal insulation depends on your climate and wall details, as there are many alternatives. The slab-on-grade should always be poured over a thick vapor-barrier..

Opps... ramble...

Rob

[colterphoto1]

DUDE!! Picky and Mike Hurd (as well as the consummate prof. Artto) have all the right ideas. Anything touching concrete should be pressure treated, the dimpled foam is a good idea, double stud walls are okay anywhere, but do not let fibreglass insulation sag and touch the outside walls (I wedged my stud wall between floor and ceiling joists, then ran several courses of thin wire along backside to keep insulation away from concrete), Vabor barrier should be used ON THE LIVING SIDE of any exterior wall, since it is people who make the vapor.

WARNING WARNING WARNING

Supposed to be putting up the outer insulation and drain pipes inside and outside on monday, then backfilling, then hopefully start seeing some wood go up! Should I be concerned with direct wall or floor contact with this set up?

WARNING WARNING WARNING

I WOULD NEVER backfill a foundation until AFTER at least the first floor is framed in. There is nothing supporting the top of the concrete/block walls until some framing is done on top. It would be a massive mistake to put the pressure of earth/bulldozer/water against the sides of an unsupported wall. Please check with your builder at once! Also make sure they have the appropriate drain pipe and sump system installed prior to backfilling. Lots of times builders will also apply a 1-2" layer of yellow dense fibreglass insulation to the waterproofing 'tar'. This allows thin air spaces for water to travel down to the drain system instead of putting pressure against the wall. You cannot beat water, only attempt to control it.

Hope this helps, didn't mean to panic you.

Michael

[Champagne taste beer budget]

DUDE!! LOL You're a little late to the dance, but thanks for the thoughts. The outside walls are poured concrete, backfilled a couple weeks ago with no problems. Drains inside and outside, no sump. They are hopefully finishing with the roof today, so any worry about structural integrity is behind us now. At least I sure hope so!!!

[Dale W]

Two sided vapour barriers have been used for years and years now in basement applications. More often then not , in northern climates.

Method involves ( as stated above ) laying 6 mil plactic against the cement wall and running it out 2 feet onto the floor and ceiling. The new wall is then slid into place , once insulated the floor section and ceiling sections are brought up or down ( whichever is the case ) and stapled into place . The next vapour barrier is now attached before drywalling .

The thinking behind this method is to prevent moisture from getting to the studs or insulation by means of migration from the cement or a newly formed crack in the wall, if moisture was present then it would run down the wall and out underneath the bottom plate of the wall and not effect the insulation or studs.

Small amounts of basement flooding would also not effect the studs and insulation but just damage the drywall.

Thats the vapor barrier issue . Building a secure / decent / proper wall that will resist unwanted vibration and aid in sound deading is another topic alltogether.

PS: walls and insulation don't need to breath , they need to be constructed properly right from the start then sealed tightly so water vapour and bugs cannont enter . 75% of the basement construction in my area is all done with steel studs instead of wood for A) cost ease of construction C) time savings and zero mess ( ie : dust from cutting ) All you need is a pair of tin snips and a screw gun .

[colterphoto1]

Good, your builder is on top of it. Many times around here we see the basement poured/laid and it's weeks/months before the framing gets completed. Plus Indiana used to be a swamp, so we've got ground water out the wazoo.

No worries mate, you've got strength now! Are you going to put in internet and audio wiring while walls are open? If so, remember to not run them for any distance alongside any AC wiring. Just a hint. Have fun.