Then, lay a 6-mil plastic moisture barrier underlayment to further protect the material. On top of that, you should install any plastic foam underlayment provided by the manufacturer.
With a concrete subfloor, you will need an underlayment that acts as a vapor barrier in order to prevent moisture from penetrating through to your laminate installation. The normal choice is a thin foam pad material made of polyethylene or polypropylene, which rolls out in sheets.
Moisture Concerns
Water concerns in the basement are serious, and most recommendations warn against installing laminate below grade at all. If you are concerned about moisture sabotaging the quality of your new laminate flooring, it pays to invest in a floor underlayment that was designed for such purposes.
For concrete or wood subfloor use of rubber or foam underlayment is recommended. When laminate flooring is installed on concrete there are many factors that should be taken in account. First and probably most important factor is humidity of concrete surface.
If you're installing laminate flooring over a subfloor, like concrete, you may want to install an underlay with a vapor barrier for added protection against moisture. Make sure you choose an underlay that works with an attached pad. Our top choice is Sentinel Protect Plus Underlayment.
Begin installation by laying a plastic vapour barrier (minimum 6 mm thick) or any other manufacturer-recommended barrier on the concrete subfloor to prevent moisture from reaching the laminate flooring. Use vinyl tape to secure the barrier and keep it from coming out.
You'll typically need a vapor barrier if you're installing flooring over concrete. Therefore, in high-humidity areas, moisture will move to a relatively low-humidity area, even through concrete.
Laminate flooring can be installed over basically any flat and level surface, including wood subfloors, hardwoods, tile, concrete and more. It is not recommended to install laminate flooring over a soft surface, like carpet, because it doesn't provide enough support for the flooring.
In some cases, there may be an issue with the concrete subfloor, such as water damage or uneven flooring. This can result in moisture building up under the laminate floor and causing mold growth on the underside of the planks.
Without underlayment to add a layer between these damp subfloors and the surface flooring, your laminate can quickly become wet, warped, and mildewy, harming its overall integrity. Moisture over time can also break down floor adhesive which causes the floor to start warping.
The most suitable materials for basement flooring are those that are waterproof or moisture-resistant. These include vinyl, engineered wood, rubber, and even carpet as long as it's marine-grade. Tiles made from porcelain or ceramic are also suitable.
Basements, because they're below grade, are prone to excess humidity and moisture, which can cause mold growth and other problems. Installing a vapor barrier in your basement will help reduce the risk of damage by preventing water vapor from getting inside while also keeping your basement temperature more consistent.
Plywood underlayment is typically needed when a floor material must have a very smooth, flat surface. For example, if you install resilient tiles or sheet flooring over a subfloor, any bumps, dips, or voids in the subfloor may be evident in the finished flooring.
Basements in Depth
Solve common problems and turn unused square footage into new, functional areas for gathering. Waterproof laminate flooring is the best option for covering a basement floor.
The American Concrete Institute (ACI) also recommends a minimum of 10 mil polyethylene or thicker for vapor retarders under concrete. According to its Guide to Concrete Floor and Slab Construction ACI 302.1R-15, thicker poly provides a better barrier and is also more puncture resistant.
Vapour barriers are materials used for damp proofing. The best approach is to lay a sheet (also called a membrane) of PE plastic 0.2mm thick beneath laminate flooring. Sheets are available in different sizes. A single sheet measuring four by four metres is large enough to cover most rooms.
Laminate ranges from 6-mm to 12-mm and, as a rule, it shouldn't be less than 8-mm. If, however, budget is an issue and if your subfloor is level and debris-free, you might be able to get away with 7-mm; keep in mind that subfloor imperfections can telegraph to the surface floor, so make sure it's okay.
Use a proper underlayment between the concrete slab and the flooring if necessary. This is especially true when using wood flooring. Installing a plywood underlayment can add extra protection, but it must also be tested to ensure it's not bringing in new moisture.
Install a plastic vapor barrier: If your concrete passes the moisture test, then plastic sheeting at least 6 mils thick will prevent moisture from getting into your laminate flooring. Where plastic sheets must be joined, overlap the sheets by several inches, and use strong vinyl tape to secure them.
Plastic Vapor Barrier Rolls
This is the top choice for contractors and DIY homeowners. Rolls of plastic (polyethylene or “poly”) are available from 6 mils to 20 mils. Rolls are typically about 3 feet to 10 feet wide. Start at an edge/corner, and roll out the barrier, and cut it at the far wall.
If your basement is semi-finished and there's any questions around moisture, either from the concrete floor below or from air humidity, then we recommend a water-resistant or waterproof laminate flooring, while also bearing in mind what we have already discussed regarding correct installation.
Don't install your laminate on any floor with a drain. Don't install laminate on any uneven subfloor or outdoors. Don't install your laminate over residential carpet. Don't install a second layer of laminate underlayment.