ᐅ Laminate Flooring in the Basement: Should You Use a PE Film Even with a Vapor Barrier?
Created on: 22 Oct 2018 09:02
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cybergnomC
cybergnom22 Oct 2018 09:02Hello,
we are planning to install laminate flooring in the basement. It is often said that a vapor barrier should be placed under the laminate in the basement. Does this still apply if there is already a wide vapor barrier applied on the raw concrete floor?
And if yes, why is it that only in the basement does laminate require a vapor barrier underneath, but not on the ground floor and upper floors?
Thanks!
we are planning to install laminate flooring in the basement. It is often said that a vapor barrier should be placed under the laminate in the basement. Does this still apply if there is already a wide vapor barrier applied on the raw concrete floor?
And if yes, why is it that only in the basement does laminate require a vapor barrier underneath, but not on the ground floor and upper floors?
Thanks!
Hello questioner.
Laminate flooring is not suitable for basement rooms that have been designated in the planning stage for secondary use only (and thus not as living space).
A vapor retarder installed on the raw concrete floor slab does not protect the layers above it (including the cement screed) from slow moisture absorption. First, a concrete slab in direct contact with the ground always contains a significant amount of residual moisture, and second, a vapor retarder cannot completely stop the movement of water vapor (there is no such thing as a “vapor barrier”; if anything, it is a waterproof membrane or a vapor retarder).
While a concrete slab foundation can only release its residual moisture upward, this is different for concrete floors in inhabited upper floors. There, residual moisture can move both upward and downward depending on the vapor pressure gradient.
Another note:
In a pure basement room (and not a living space), there is no thermal insulation (and usually none is needed).
So, if you install laminate flooring directly on cold concrete and use the room regularly, for example as an office, the dew point will be reached on or possibly under the laminate panels. Moist air can then condense into water there.
Since the core boards used for laminate flooring are generally made of moisture-sensitive wood-based materials, deformation and swelling cannot be ruled out.
There is, however, an alternative for installation:
Laminate flooring panels designed for use in bathrooms. These core boards are moisture resistant and much less likely to deform.
Good luck: KlaRa
Laminate flooring is not suitable for basement rooms that have been designated in the planning stage for secondary use only (and thus not as living space).
A vapor retarder installed on the raw concrete floor slab does not protect the layers above it (including the cement screed) from slow moisture absorption. First, a concrete slab in direct contact with the ground always contains a significant amount of residual moisture, and second, a vapor retarder cannot completely stop the movement of water vapor (there is no such thing as a “vapor barrier”; if anything, it is a waterproof membrane or a vapor retarder).
While a concrete slab foundation can only release its residual moisture upward, this is different for concrete floors in inhabited upper floors. There, residual moisture can move both upward and downward depending on the vapor pressure gradient.
Another note:
In a pure basement room (and not a living space), there is no thermal insulation (and usually none is needed).
So, if you install laminate flooring directly on cold concrete and use the room regularly, for example as an office, the dew point will be reached on or possibly under the laminate panels. Moist air can then condense into water there.
Since the core boards used for laminate flooring are generally made of moisture-sensitive wood-based materials, deformation and swelling cannot be ruled out.
There is, however, an alternative for installation:
Laminate flooring panels designed for use in bathrooms. These core boards are moisture resistant and much less likely to deform.
Good luck: KlaRa
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cybergnom22 Oct 2018 17:54Hello KlaRa,
thank you very much for the detailed response.
In our case, the basement is insulated on the outside, and on top of the vapor barrier there is a 6cm (2.4 inches) styrofoam insulation layer, plus 2cm (0.8 inches) impact sound insulation. The entire basement has underfloor heating. One room is regularly used as an office.
Additionally, a controlled mechanical ventilation system is installed.
Is it still necessary to put a foil under the laminate flooring?
thank you very much for the detailed response.
In our case, the basement is insulated on the outside, and on top of the vapor barrier there is a 6cm (2.4 inches) styrofoam insulation layer, plus 2cm (0.8 inches) impact sound insulation. The entire basement has underfloor heating. One room is regularly used as an office.
Additionally, a controlled mechanical ventilation system is installed.
Is it still necessary to put a foil under the laminate flooring?
If I may join in here:
In our basement, a waterproofing membrane with bitumen (A*ujet) was applied on the ground slab made of waterproof concrete (WU concrete), followed by polystyrene insulation and screed.
Is a polyethylene (PE) sheet still needed here, or can the screed be covered directly with elastic floor coverings such as linoleum or rubber?
In our basement, a waterproofing membrane with bitumen (A*ujet) was applied on the ground slab made of waterproof concrete (WU concrete), followed by polystyrene insulation and screed.
Is a polyethylene (PE) sheet still needed here, or can the screed be covered directly with elastic floor coverings such as linoleum or rubber?
WU concrete, meaning concrete designed to be waterproof, is always permeable to water vapor! In physics and building physics, we differentiate between the various states of matter. For example, WU concrete limits water penetration into the cross-section up to a water pressure of about 5 bar (I believe it corresponds to 5cm (2 inches) water column). Water vapor pressure, however, passes through the structure regardless of the water-to-cement ratio, always moving from higher to lower partial pressure. In the case of a ground slab, the lower pressure is always in the space above it.
This means: YES, it is still necessary to install a PE foil as a vapor barrier on the screed. This remains the current state of the art as well as the recommendation in most installation instructions from manufacturers of floating laminate flooring (unless the products are specifically rated for wet areas by the manufacturer).
Regards, KlaRa
This means: YES, it is still necessary to install a PE foil as a vapor barrier on the screed. This remains the current state of the art as well as the recommendation in most installation instructions from manufacturers of floating laminate flooring (unless the products are specifically rated for wet areas by the manufacturer).
Regards, KlaRa
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