Moisture Barrier for Laminate Flooring

There is always the question of whether a moisture barrier is needed when dealing with flooring. The answer is yes, it is required. A moisture barrier can also be called a vapor barrier, and it is used to protect your floors from moisture damage.

It is a piece of PE plastic sheet material placed underneath laminate flooring used for damp proofing; it slows down moisture from moving through your floors, thereby protecting it from damage.

Simply put, this barrier prevents your floors from vapor damage which makes it a necessity in your home. Materials made from polypropylene and polyethylene are the best moisture barrier options for your laminate flooring. It is difficult for liquid to pass through these materials; an example is a plastic sheet.

Moisture Barrier for Laminate Flooring

Do you need a moisture barrier under laminate flooring?

Why is a moisture barrier necessary? Your floors get damaged in cases where your flooring gets wet. The base of a laminated floor is manufactured from wood, making it susceptible to spoils when it comes in contact with water vapor.

The wetness can cause your flooring to swell; it can also cause mildew and mold, which will never be a pleasant sight. The best and most straightforward way to avoid damage to your floors is to use a moisture barrier.

Best moisture barrier option for laminate flooring

Now you know that a moisture barrier is an excellent choice for your laminate flooring, the next thing you should be aware of is the best material to do the job. The commonly used option is plastic, as it is an excellent option.

Plastic is known for its ability to control moisture; water as gas and as a liquid cannot travel through it. This is why it can be a moisture barrier. When picking a plastic sheet, you should go for polyethylene plastic 6-mil thicker or above.

The thickness for every moisture barrier ranges from 6-mil to 20-mil. It all depends on how sturdy you want your barrier to be. Your location is also a factor for choosing thickness. For damper areas, you should pick something significantly above 6-mil.

Plastic remains your best option. Apart from plastic, you can use any other underlayment that has a moisture barrier infused in it. Vapor barriers are classified into three different categories based on their permeability:

  • Class I vapor retarder: These materials have 0.1 or less permeability. It is difficult for fluid to travel through these materials, making them the most substantial moisture barrier. Examples are sheet polyethylene, glass, sheet metal, etc.
  • Class II vapor retarder: these materials have more than 0.1 but less than or equal to 1.0 permeability. They are referred to as semi-permeable, which means that fluid can pass through, but not all. Examples are plywood, expanded polystyrene, etc.
  • Class III vapor retarder: these materials are very absorbent as fluid can pass through them. They have more than 1.0 but less than or equal to 10 permeability. The worst options for moisture barriers. Examples are gypsum board, concrete block, latex, enamel paint, brick, etc.

Moisture barrier for laminate flooring over concrete

After installing laminate flooring over concrete, the next important thing is to add an underlayment. You should always add a moisture barrier underlayment to subfloors that are not absorbent.

Concrete is hard, but that does not mean it can absorb water. It is porous, meaning water can readily travel through it, causing warping and damaging your laminate flooring.

The first thing you should do is carry out a moisture test on your concrete. You can use any material made from polyethylene and polypropylene like plastic. This is why it is essential to use a moisture barrier for your laminate flooring over concrete.

After this test is carried out, you can place your moisture barrier as an underlayment. A 6-mil plastic sheet is suitable enough and will prevent the moisture from penetrating and damaging your laminate flooring.

Acceptable moisture levels for laminate flooring

To prevent the expansion of laminate flooring, your humidity should not be less than 30-35% and more than 55-60%. The in-between is the perfect environment for your laminate floors. If it surpasses 60%, the sides of each plank will be pushed into each other and will end up buckling.

If it is below 30%, the sides of each plank will be pulled away from each other, thereby causing the gaps in your floors to be shown. The best way to properly enjoy your laminate flooring is by acclimating them.

Acclimation is the process of keeping your laminate flooring packaged in the area where you want to install it for 24-48 hours. This enables the flooring to get used to the level of moisture (it contracts accordingly) in that environment.

Importance of moisture barriers for laminate flooring

The importance of moisture barriers can also serve as the factors you should consider, which help to determine whether you need a barrier. These are subfloors, climates, and grade levels. They are explained below.

  • Climate– Moisture barriers serve as a vapor diffuser during the rainy and snowy climate season. If you are the type that lives where weather conditions are always on the extreme, a barrier will help to keep the recurrent vapor from damaging your floors.
  • Subfloors– Not all floors are absorbent; without a moisture barrier, they will end up damaging your flooring. For example, concrete floors are porous. Once a barrier is added before placing your flooring, you can rest assured that your flooring will be protected from vapor and moisture.
  • Grade levels– Moisture barriers do a great job protecting ground and basement floors in the home from moisture damage. The lowest level of one’s house is more prone to damage than the highest levels are. This is why a moisture barrier is needed.


Now you know the benefits of having a moisture barrier for laminate flooring. It is essential always to protect your floors from vapor damage, which is one of the best ways to do. Remember to consider the climate area you live in, the subfloors in your home, and the level of your home prone to moisture.

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