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Vinyl plank flooring over concrete in a basement

I am doing the design to upgrade the basement of a house in Leadore, Idaho, 83464. A vinyl plank floor has been requested, to minimize the loss of headroom.

I've never worked with the vinyl plank before, and have some hesitancy about specifying it directly over the concrete. The building is built on an extremely well drained alluvial gravel, and the landscaping drains away from the building, so I don't expect any issues with water penetration, but I am concerned with the moisture wicking in from the slab, and condensation from the air.

Is the vinyl plank going to breath enough through the seams that I don't need to worry about transfer through the concrete, or should I be considering some form of water/vapor proof barrier system that will elevate the vinyl enough to allow evaporation?

Asked by Randall Thomas
Posted Aug 7, 2017 2:55 PM ET
Edited Aug 8, 2017 11:51 AM ET


6 Answers

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I'm curious. Has this basement been radon tested? Idaho looks like a hot spot on US EPA radon maps. I would think trying to get the concrete to breathe through the flooring or perimeter would be contrary to radon management.

Answered by Keith H
Posted Aug 7, 2017 5:47 PM ET


I have epoxy covered basement concrete with no condensation. But I do control humidity with dehumidifiers.

Answered by Jon R
Posted Aug 7, 2017 6:27 PM ET


Neither vinyl nor concrete is harmed by moisture, so why is this even a concern?

Answered by Dana Dorsett
Posted Aug 7, 2017 6:30 PM ET


Vinyl with condensation on it wil feel cold and clammy under foot. This is summer housing so it won't be a big issue. Just trying to think out the issues ahead of time.

The building has a retrofit sub-slab vacuum system installed and is monitored annually with digital meters as an indicator of general function. Radon levels are highest in the winter, when the ground is frozen, and air exchanges are lower, as people move in and out of the buildings less. So peak levels are highest in January through March. If the digital monitor is high, then we deploy the long term canisters, and monitor for a year.

Answered by Randall Thomas
Posted Aug 8, 2017 8:10 AM ET


The first step is to consult the installation instructions provided by the flooring manufacturer. Any reputable flooring manufacturer should publish installation instructions that will tell you the details required by the manufacturer for installation over a concrete slab. Note that some types of flooring cannot be installed on below-grade slabs.

If this information is not available from the manufacturer, call up the manufacturer and ask to speak to a technical representative who can provide installation details for your situation.

In general, it's usually not a good idea to install any type of finish flooring over a basement slab unless there is a continuous layer of rigid foam insulation -- either under the slab or between the slab and the flooring. People break this rule occasionally, but it's usually unwise to do so.

Answered by Martin Holladay
Posted Aug 8, 2017 9:03 AM ET


Summertime condensation isn't ground moisture, it's the moisture of the room air condensing onto the cold slab/flooring. In your case you even have the radon system purging ground moisture from beneath the slab.

In most of ID summertime condensation on the floor not a huge issue, especially if the house is air conditioned (with conventional AC, not a swamp cooler). The deep subsoil temperatures are in the mid to high 40s Fahrenheit,and the summertime outdoor dew points average in the low 40s. Even a half inch of EPS (R2-ish) between the slab & flooring/subfloor would be enough to keep the vinyl plank tracking much closer to the average room temperature, well above the subsoil temperature.

Answered by Dana Dorsett
Posted Aug 8, 2017 10:18 AM ET

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