Using Laminate Flooring in Basements: What to Know

Traditionally, laminates have not been recommended for below-grade basement installations due to issues with rising groundwater and flooding. However, new manufacturing techniques now produce lines of laminate that are rated to deal with moist, subterranean locations. You can ensure that a particular laminate is good for basement use by carefully reading the stipulations in the material warranty.

Common Problems With Laminate Basement Flooring

Groundwater: A basement’s subfloor usually consists of a concrete slab that acts as the foundation for the structure. This slab is surrounded by earth that contains various amounts of water depending on rainfall and humidity. In older buildings, there usually is no vapor barrier between the earth and the concrete, and this allows moisture to slip from the ground into the slab and up to the surface floor. Applying a waterproofing agent to the concrete slab prior to installing laminate flooring is a good practice.

Basement humidity: Basements are often very humid areas. Surrounded by moist earth, basements are usually cooler than the rest of the house, and this allows ambient moisture in the air to condense. When it rains, the saturated soil around the basement can cause a basement to feel particularly muggy. This humid air can then seep through cracks and seams, causing the laminate flooring material to warp or rot.

Below-grade flooding concerns: Basements are susceptible to flooding for several reasons. In a general local flood, such as may happen in the springtime, the water that fills the streets will naturally spill down into any lower areas. Even a heavy rainfall that saturates the ground can cause water to spill in through the concrete walls and subfloor. In many homes, the washing machine, water heater and similar appliances may be kept in the basement, and if any of these appliances malfunction, flooding can result. 

Picking a Laminate Basement Flooring

Most traditional laminates are made with a waterproof surface layer, a decorative layer, and then fiberboard backing. This backing is what is susceptible to moisture, and if it comes in contact with liquids it can warp, twist, rot, and start to grow mold and mildew. There are new laminate materials that are manufactured to be resistant to water. In a basement environment, the best choice is going to be a laminate that is built with a solid plastic core. This will nestle the decorative sheet between a waterproof wear layer and an impervious plastic backing to create tiles that are resistant to almost all liquid penetration.

Test for Moisture Before Installation

Before you install laminate flooring in your basement, you should do a plastic sheet test. This is a fairly simple test to check for moisture in the concrete slab.

1. Cut plastic garbage bags into squares, and then tape them to the floor in various places around the basement.
2. Then leave them for three days.
3. At the end of that time, lift the squares to see if moisture has accumulated on the bottom of the plastic. If it has, your basement may be too moist for a laminate flooring installation.
   

There are more advanced moisture tests that use chemicals to detect the presence of liquids. Others require you to chisel a hole into the concrete and use an electric meter to take a reading. All of these tests have varying degrees of accuracy and should be undertaken multiple times in multiple places throughout the basement.

How to Install Basement Laminate Flooring

You should only install laminate on a concrete basement subfloor which was poured 60 days or more prior to the work. Newer concrete will still be losing moisture that can affect your flooring installation. You also need to keep the installation environment at a steady 60 F to 75 F, with 35 to 50 percent humidity or less for a minimum of 15 days prior to starting the installation.

1. Start by sealing the surface of the concrete with a chemical sealing agent that will create one more barrier between the base of the laminate, and any groundwater that may seep up over time.
2. Then, lay a 6-mil plastic moisture barrier underlayment to further protect the material.
3. On top of that, you should install any plastic foam underlayment provided by the manufacturer.
4. Install the laminate flooring over that prepared slab and underlayment.
5. During the installation, follow all of the manufacturer's instructions exactly. It’s also a good idea to check the warranty on the material to ensure that your installation procedure does nothing to void it.