Do I need a vapor barrier on an 8" pour + carpeting over tile?


I want to insulate the ceiling in my garage. When the house was built 10 years ago, the walls attached to the house were done, and the ceiling was drywalled (Fire code). However, they did not put a vapor barrier, before drywalling. I live in Canada. Winter is about six, seven months long. I have access to above the garage. Should I staple a vapor barrier over the joices, and in between, then put my insulation?

I just want to be able to work in there once in a while, over the winter. I already put vapor barrier and insulated the outside walls. Going to heat it with a couple of ceramic heaters. The roof is well ventilated, with soffit vents, and a whirlybird. The roof is made with 2x4 trusses on two foot centres, and they used metal channeling to screw the drywall to.

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The person you spoke to at the store, is giving out wrong advice.

Cement board is in no way, shape, or form....any kind of a vapor barrier, nor is it rated as such. Thus, it cannot be a "membrane" in a vapor chamber, that the person you spoke to, insinuated.

As an example, from Durock's website (
"Durock (Cement)Board is "Water durable" - will not rot, warp, delaminate, or disintegrate when exposed to water."

Cement board, or fiber-cement board, will not breakdown with moisture, like the way sheetrock does. In that way, it is superior. However, like all cementitious material, the product is water permeable, it will take-in/absorb moisture, when it comes in contact with it. This will then be transferred to other surfaces that it comes in contact with. Thus, the need, for a good vapor/moisture barrier, and as suggested, a complete sealing of the installed board's seams themselves.

FWIW: Even...

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My shower is against an outside wall. It was not insulated so I did that. I am going to put up hardibacker, then Redguard, then thinset, then tile. Do I need the 6 mil vapor barrier between the studs and the hardibacker or is this a really bad idea? This might be too much of a good thing?

ONE vapor barrier, not two...Choose your poison, Redgard or plastic.

Would you recommend one over the other? I live in Oregon so the last thing I need is excessive moisture in/around the house! My contractor (although this is a DIY project) had never heard of Redguard and just recommended the vapor barrier.

If this is a custom shower base,(rather than a preformed plastic base), I can only see one flaw with that method, that being the backerboard,(Hardie), wicking water from the bottom edge. The surface membrane is a good idea, but it has to overlap the floor membrane or pan material without being pierced by fasteners. Thus allowing water to run down the walls and because it...

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Without just reading other answers, which may offer valid suggestions, my suggestion is OVERKILL can't hurt.

I tile every day of my life and have done Bath Rooms more than much else.

Certainly sealing the seams/butt joints will help.

Since you have a TUB, I'll assume it has an UP LIP that butts to the wall. Your backer and tile can extend to the tub, below that lip, and after the fact be caulked. That would also apply to a plastic tub/shower surround. The enginerring in the LIP is to avoid water getting behind the TUB, and.or wall finishes to the studs, insulation, flooring, etc.

A simple SHIM could be a piece of lumber the thickness of a grout line, on the tub, horizontal lip.

Steven Wolf
Just my two...

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Anyone that has had to face a moisture problem with a concrete slab understands the damage that excess moisture can cause. Moisture in concrete can occur from a variety of sources: ground moisture that contacts the slab through either capillary action or as water vapor, high air humidity or drastic changes in relative humidity in its environment, leaking plumbing that passes through the slab, and more.

Excess moisture can cause pH changes in concrete that adversely affect adhesives. Even an excess of moisture that was retained from the original concrete mixture will cause problems if the slab was sealed prematurely.

It should be obvious – concrete starts wet. The water added to the cement, sand and aggregate mixture is necessary to form a good bond in the concrete, but it is also necessary that the moisture evaporates away from the concrete in order to let the concrete dry and to prevent flooring failures.

Adding more water may make concrete more...

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An ounce of prevention is worth a pound of cure.

Back in 1922 when I was young I was told that is the only to look at doing home repair projects.

If you have a older home, the poly barrier is considered the same as the kraft-faced insulation, just tightens up any chance of air movement.

There has been issues of walls "sweating" in regards to the poly barriers ontop of kraft faced but that was limited to super airtight homes, tyvek outside house wrapped and the fear of radon exposure in the home.

If you have an older home, more than likely the house has enough openings that allows the house to breath which is considered better in some circumstances. < That statement right there alone has probably saved lives with homeowners with leaking heat exchangers in furnaces that are emitting Carbon Monoxide.

Click to...

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From basements to baby rooms, carpet tiles will complete your space. (Dante Carpet Tile Lark Collection – Dark Brown Stripe)

Carpet tiles are colorful, versatile, and easy to install, making them the perfect comfort flooring option for homeowners and renters interested in do-it-yourself projects. What’s more, carpet tiles can be placed over existing floors, eliminating the time and effort needed to remove old flooring and flooring adhesive.

While laying carpet tile is a simple process, carefully taking things step-by-step will help ensure the tiles lay evenly and correctly, and last longer. That being said, here are the 7 key steps you should follow if you choose to install carpet tiles in your own home or rental.

Tools & Materials

measuring tape Carpenter’s square chalk line utility knife with a heavy-duty blade adhesive (either peel-and-stick Rightbac tape or dri-tac glue) u-notch trowel for applying adhesive

1. Choose a pattern

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A concrete vapor barrier is simply a sheet of polyethylene plastic (Visqueen) placed directly on top of the sub-grade before the concrete floor or slab is poured to help keep moisture from the soil from passing up through the concrete.

Many moisture problems associated with interior concrete floors and slabs on grade can be minimized or eliminated by installing a vapor barrier under the concrete.

A vapor barrier should be used for all concrete floors and slabs that are going to receive an impermeable floor finish like epoxy, laminate, linoleum, and wood or if the concrete floor will be used for any purpose where the passage of water vapor through the floor may create problems.

Water vapor that passes through the concrete will evaporate if the concrete surface isn't sealed or covered by a material that doesn't allow the concrete to breathe. Floor coverings like linoleum, vinyl tile, wood, carpeting, and epoxies, seal the moisture in the concrete where it...

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This podcast series is excerpted from a two-day class called "Building Science Fundamentals" taught by Dr. Joe Lstiburek and Dr. John Straube, of Building Science Corporation.

For information on attending a live class, go to

In our last episode, Dr. John Straube argued that building energy-efficient buildings takes just a little extra thought but makes economic sense. In this show, Dr. Joe Lstiburek offers a simple comparison between air barriers and vapor barriers, and warns that we need to worry more about airtightness if we want to keep our homes healthy and dry.

Smaller holes mean less moisture in your wall
You have to understand the difference between air and vapor. Vapor barriers can be ripped and torn and full of holes because the amount of water vapor that passes through due to diffusion is very small compared to the amount of water that can go through a hole or a crack due to an air pressure difference. I...

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When installing hardwood floors, you want to protect your investment whether it’s a $0.69 laminate or a $6.69 exotic hardwood. Moisture is a big concern for flooring, you definitely don’t want it! And we’re not just talking about some water spilling or snow being tracked through the house (although, to help with that, we do recommend putting down rugs at home entrances and in front of sinks). Moisture can come up through your subfloor, especially if you are installing over concrete or below-grade. A moisture barrier is need to protect the flooring against moisture or moisture vapor. Along with the moisture barrier, you may want to install an underlayment. It insulates and cushions the flooring, making it more comfortable to walk on.

For moisture barriers, there are three basic methods of protection:

Nail Down Installations – In crawl spaces under the subfloor, 6 mil poly sheeting plastic should be placed over the dirt. IN addition, a 15 lb felt paper should be placed...
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Location of the VB (if any is used) is very important and it should always be on the warm side of any insulation you're installing. That means, in case of walls, just behind the sheetrock or plaster. Unless you've got your walls open now, it's impossible to install a VB behind the surface. (There are VB paints, and you can choose some VB wallpaper-type things.)

The point of the VB is to block transmission of moisture from the home into the insulation, which in a cold climate like yours will be much colder during the winter. Vapor that escapes from the warm, moist, air indoors can condense within the insulation material itself when the temperature inside the insulation hits the dew point. The potential damage posed by this is creation of a long-term saturated area within the insulation, lowering its effectiveness and possibly migrating to adjacent concealed wooden parts of the structure and creating rot problems.

Many people confuse the ubitquitous house-wrap (Tyvek,...

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Get a buddy to help. I managed to recruit my dad to help with some of this.

In anticipation of my 200 pound shower door I put 4 studs in the left side of the shower wall. Definitely not overkill in this application in my opinion.

After the space was framed out with 2x4's I used 1 1/2 inch styrofoam insulation to insulate the walls. When you need to make cuts in the styrofoam it's easy. Just score with a utility blade and snap the score along a 2x4 (or large work bench) to fit between studs. Next staple 4mm vapor barrier onto the studs covering the entire area using a staple gun.

The best part is hanging the concrete board. Use 2 1/2 inch concrete screws for this. I was concerned about the weight of the tile that was going up so I used long screws.

Once the concrete board is up mix morter according to package directions and apply to cracks of concrete board using a flat trowel to smooth and seal. Use silicone caulk for the corners and where you aren't...

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