What is best vapor barrier for second floor bathroom on a concrete slab?

The info on this forum has been very helpfull, but I still have some questions regarding the concrete sealer.

I will start to finish my 900 sq. ft. basement in a few months, but before I begin the drywall and bathroom piping, I would like to seal the concrete. The slab and walls were poured about 5 months ago and I live in Atlanta, GA.

I will probably install a glue down engineered wood floor directly on the concrete slab, but which sealer should I use as a vapor barrier?

You mentioned a 2 part epoxy sealant, but would that be enough vapor barrier to simply glue down the wood floor later? Any brands you recommend?

I was considering a product called RadonSeal Standard http://www.radonseal.com/concrete-sealers.htm
Penetrate deep (up to 4" in concrete) and react with lime and alkalis. Bond and strengthen, reduce cracking. Harden the surface and reduce dusting. Seal against water seepage, water vapor and radon gas. Withstand high water pressure. Reduce indoor...

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I'm having issues with dampness around certain parts of the house. Around the room corners . Seems the the slab foundation is wicking up moistutre. Carpet feels damp, moisture midew smell. I want to remove the carpet and pad and seal the slab. I've already applied a product to the exterior below grade. It's helped, but not completely. It was called liquid rubber. Any product suggestions? or ideas?

Can it help? Well sort of.......

That whole idea of concrete sealers is a bit of a snake pit.

Lots of claims, scams and some snake oil sales.

Understand the basics up front.

Good concrete will not pass water if it is of an excellent grade and strength rating. Most home contruction is usually of a crap grade of concrete, so there is the core problem. The problem starts in the initial selection of the concrete, at the root of the problem in not enough cement in the mix. Also understand concrete is a chemical function, the process...

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All of the problems associated with moisture vapor movement in a concrete slab will go away in time as the slab dries, as long as there is no source of additional water into the slab. Since the most common source is moisture in the ground beneath the slab, the solution is to completely take the ground out of the equation, by sealing the bottom of the slab.

The best way to accomplish that is with a vapor barrier under the slab. Vapor retarders have been used since the 1950s. Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons:

Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through. 6-mil plastic often gets damaged during placement of reinforcement and concrete, creating holes that can let a considerable amount of water vapor into the slab.

True vapor barriers allow little water vapor to penetrate. W.R....

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By Joseph Lewitin

Updated March 13, 2016.

There are a number of challenges that face a bathroom floor on a daily basis, including water concerns, humidity changes, and staining agents which spill and splatter. With concrete, you get a floor that is uniquely suited to handling even the toughest environmental hazards. This, combined with new print and staining techniques, allows you to use concrete as both a functional utilitarian surface, and a beautiful element of interior style.

Concrete Flooring Design and Image Gallery

Concrete Floors and Water

Below The Surface: If you are removing existing floor coverings in order to use the concrete block that the building rests upon, then you may need to be concerned about moisture penetration in the slab, from below. That is because concrete foundations rest directly on the ground soil that surrounds them. This soil can become saturated with moisture, which can rise up into the slab via...

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My opinion of the best concrete floor vapor barrier

Photo courtesy of Stego Industries, LLC

What is the best concrete floor vapor barrier?

That’s a great question! I’ll get to that in a minute.

Another great question is; why do you need a vapor barrier under your concrete floor?

I’ll answer that one first.

I’m Mike Day, my company Day’s Concrete Floors, Inc has been installing concrete floors and vapor barriers under those floors for over 30 years.

We also install coatings like epoxy paint on top of those concrete floors. Epoxy and other flooring materials are really sensitive to moisture.

Moisture vapor from the sub-grade moves up through concrete and escapes or evaporates from the surface.

Very simply, if there is too much moisture a coating like epoxy will fail causing it to blister and peel. In other words it won’t stick to the concrete.

This is why you need a real vapor barrier installed under your concrete...

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Garage slabs take a lot of abuse. They have to support heavy cars and trucks and resist ice, dirt, salty water, de-icers, gasoline, motor oil, antifreeze, and other contaminants. Plus, since few garages are heated, they have to tolerate freeze/thaw conditions. But a garage slab that has been carefully planned, installed, and cured should have no trouble providing years of crack-free performance in any climate, even under the toughest conditions. Commercial concrete contractors do this kind of work every day; adopt their attention to detail and you’ll meet their high standard of quality, without having to raise your prices.

Start with a good base

Don’t worry too much about your soil’s bearing capacity. Even poor soils like silt and soft clay have an allowable soil pressure of around 400 pounds per square foot (psf). A 6-inch-thick slab weighs only about 75 psf, and live loads — anything that is not part of the building itself, including vehicles—typically don’t...

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I’m installing a floating laminate floor on a concrete slab. Do I need to be concerned about moisture? -Gerald

Hi Gerald,

Excessive moisture is definitely a concern with laminate flooring on any subfloor, but particularly when installing it on a concrete slab. Before installing laminate flooring on a concrete slab, test the concrete first to be sure it’s dry enough:

A new concrete slab should have cured for a minimum of 30 days before installing any type of flooring, including laminate. Before installing laminate flooring on a new or existing concrete slab, test the slab with a moisture meter to be sure it has no more than a 4.5% moisture reading. Another (less accurate) way to test the moisture in a concrete slab is by taping an 18” x 18” piece of plastic to the concrete on all four sides, then allow the plastic to remain in place for 48 to 72 hours. If there is moisture under the plastic or it feels damp underneath, the slab has too high a moisture content...
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I have pergo installed in a kitchen and recently was notified by my tenants there are small bubbles of water coming up between pergo planks. The property is located in Tucson, AZ. This is a very dry climate, except in the summer during Monsoon season, which even then the humidity might hit 60% on a very rainy day.

The localized area is right in front of the sink cabinet. The pergo planks are now starting to slightly buckle. I contacted my home owners insurance company and they sent out an Adjustor. He was unable to determine where the water was coming from. He then contacted a water leak detection contractor. The water detection contractor found the swamp cooler on the roof could be the cause of water slowing accumulating under the pergo. He stated the overflow valve for the unit needed to be adjusted and the timed overflow spilling of water that drains thru pvc pipe was entering thru the roof near the sewer vent pipe. Upon inspection of roof vent pipe, this roof area is...

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By Joseph Lewitin

Updated March 13, 2016.

Basement remodelling ranks just behind kitchen and bathroom renovations as the best way to add to the value of your home. When looking at your basement with a designers eye, there will be many elements that you will want to remove, or cover up. At the same time, that concrete slab floor that is the foundation of most basements may actually have more potential for decorative beauty than you might imagine.

Whenever you work with any kind of flooring or surface treatment in a below grade basement location, the first thing that you have to do is test the moisture content of the floor over the course of several days. That is because moisture can often rise up from the surrounding ground soil, into the concrete, causing problems over time.

Testing a Concrete Slab For Moisture

If moisture content in the slab is too high, then you will have to take steps to reduce it before applying any surface treatment to the...

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I have an attached one car garage where the floor slab seems to have sunken in one corner by about an inch and a half and varies lesser amounts in other areas. The slabs continues behind the garage into our stairwell (the house in on a hill and the main living are is one level above the garage).

We want to fix the slab in the stairwell and would prefer to make the fix in the garage as well. We have so far gotten a quote for "slabjacking" using polymer foam for around $1,500. Other options are to use a special bonding top-coat cement mix to level out the slab while also inject some of the mix into the cracks about the edges. That cement mix is not cheap ($15 for a 40lb bag) but because of the thickness needed I don't imagine it would require that many bags.

FYI, we moved into the house about a year and a half ago and haven't noticed any sinking. The house is 50+ years old so the sinking may have happened...

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I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood.
Vapor barrier should be placed directly...

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With a basement remodel underway, Jeff Dieterle weighs his options for a trouble-free floor. "We want to do the kitchen and bathroom in tile or stone and the rest of the area in wall-to-wall carpet," he writes in a Q&A post at Green Building Advisor.

So far, he's found two products that would seem to work: Ditra-Heat under the tile or stone sections of flooring, and a product called Delta FL in tandem with tongue-and-groove plywood under carpeted sections.

Dieterle has never had a bulk water problem in the basement in the 17 years he's lived in the house. Even so, he's not sure that the Delta membrane/plywood combination is a good idea.

"Not fond of the T&G plywood in the basement as everything else will be mold-proof," he writes. "Are there other options beside inorganic individual tiles? Or is the Delta FL system reliable?"

That question is the start of this Q&A Spotlight.

Two potential water problems, not just one

There are two types...

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Thanks for the feedback!

It's a 35 year old 1st floor slab. It’s had Parquet hardwood for 10 years with no problems. The slab is very dry - the Polyfilm Test shows no moisture.

Floating – Mainly DRIcore. Eliminated because Armstrong said it would void the warranty.

Glue down – Plywood system over Bostik's Best and sleeper system in mastic. Sleepers eliminated due to added height. Glue down was "eliminated" in general because nailing it down seems sufficient (see original post).

Nail down – Plywood over vapor barriers vs. plywood over Delta FL (and Delta look-a-likes).

* Armstrong (I’m going with Bruce stuff) is not prescriptive on the issue of subfloor - their main guidance is the usual "Dry, Flat, Structurally Sound" etc. phrasing which covers a multitude of sins.

* NOFMA recommends plywood-on-slab or sleeper sub-flooring systems for concrete. Either is for 3/4" hardwood flooring up to 4" wide. They state to...

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Homes built on concrete slabs are good candidates for solid wood flooring, provided that the slab does not wick up too much moisture. Humid conditions, such as those found in basements, eventually cause wood floors to buckle, cup, warp or crack because wood expands and contracts with changes in moisture levels. Take a few extra steps and precautions before installing wood floors over a concrete slab.

Moisture Check

Builders typically lay down a vapor barrier before they pour a concrete slab. Concrete tends to wick water quickly, and the barrier holds back most of the moisture. Try cutting a 12-inch-by-12-inch sheet of polyethylene plastic and taping it to the slab. Make sure the edges are completely sealed with duct tape. Leave the plastic in place for about 24 hours. After that time, the plastic sheet should still be clear. You should not see any water droplets or clouding that indicates the presence of moisture. If the plastic is clear, you can install wood over...

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