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Guide to Flooring Underlayment

hardwood flooring in living room with neutral palette and wood accents

If you have plans to install new flooring, no matter what type of flooring you are going for, you will need to think about the underlayment. Flooring underlayment is the surface that sits between the structural subfloor and the surface flooring. Virtually any type of surface flooring you choose, excluding some types of vinyl flooring, requires an underlayment but the type, material, and purpose will vary with each type of flooring material. 

Underlayments can prevent the surface flooring from becoming cracked or damaged, provide thermal and sound insulation, and cushion the floor to make walking across it more comfortable. Because underlayment serves a variety of purposes, making it an essential part of any flooring project, you will find quite an extensive selection on the market. With so many options, choosing the most suitable one can be challenging but the job gets easier to tackle when you know exactly what to look for. 

Choosing the right underlayment for wood flooring

The major purpose of underlayment under wood flooring is moisture protection so this is something that you should make a priority in your search for the right flooring underlayment. The National Wood Flooring Association publishes guidelines on acceptable moisture levels in wood flooring subfloors in addition to an acceptable vapor barrier. Failure to follow these guidelines can lead to crowning, cupping, and gapping of hardwood floorboards. 

The NWFA states that asphalt laminated paper and asphalt-saturated kraft paper satisfy their criteria whereas plastic sheeting does not make a suitable wood flooring underlayment because it can trap in moisture and keep the floor from being able to breathe. As you are shopping around, you will likely also see wood flooring underlayment made of materials such as cork, rubber, and felt. These are good options as long as they satisfy the permeability requirements set by the NWFA. 

Choosing the right underlayment for laminate flooring

Just like you have to be aware of moisture affecting hardwood flooring, laminate requires the same considerations. However, laminate floors also require that the underlayment provide cushioning and insulation. A foam underlayment that is specifically designed for laminate flooring is the best choice and is available with or without an incorporated vapor barrier. If you are installing laminate flooring on the ground floor or in the basement, you should always purchase a foam underlayment with the vapor barrier. In a second-story room, however, you probably don’t need it. 

Choosing the right underlayment for vinyl flooring

If you are installing vinyl flooring by gluing vinyl sheeting to the subfloor, you should first install a layer of ¼-inch or thicker plywood first then glue the sheeting to that. 

When installing vinyl plank flooring, you won’t need an underlayment since the planks are already engineered with their own underlayment. However, if you are installing click-lock vinyl tiles or wood-plastic composite planks, you should install an underlayment since both of these products are vulnerable to moisture damage. 

How to install flooring underlayment

Prior to installing an underlayment, it’s essential that you level the subfloor especially when you are replacing carpeting with wood, laminate, tile, or another equally inflexible material. Start by sealing cracks between plywood sheets with patching compound or self-leveling floor compound.

The method of installation will depend on the underlayment material. Most commonly, installing paper or foam sheeting is stapled to the layer below.