The Best Way to Cover Old Floor Underlayment

Underlayment

• "Underlayment" is the term used to describe the subfloor, foam and other types of barriers placed underneath the top flooring material. Flooring that is glued to the surface typically only needs a subfloor underlayment, such as plywood or concrete. Laminate, engineered and floating floor surfaces, however, require a second underlayment, usually made from a foam material.

Condition of Old Underlayment

• If the old underlayment is in good condition, you don't need to replace it. A subfloor should be smooth and not have bumps and divots, especially when laying a vinyl flooring since you'll eventually see the subfloor flaws take shape on the vinyl. If you can't repair the subfloor with a compound or remove it, cover it with a 1/4 inch thick plywood subfloor. Cut the wood to fit and secure with ring-shank nails. Maintain a distance of 1/32 inch between the boards and a 1/2-inch gap between the subfloor and wall to allow for expansion as the weather changes. If the foam underlayment is in disrepair, discard it and start over with a new one.

Foam Underlayment

• When laying down a floating wood floor, or an engineered or laminate flooring, you'll need to lay a separate underlayment on top of the subfloor. It's usually made from foam. Simply roll it out and cut the ends with a pair of scissors to fit the entire area of the floor. Do not glue it to the subfloor. Then, install the flooring on top of the foam underlayment.

Other Tips

• The thickness of the foam underlayment does not help cushion the flooring like thicker padding cushions a carpet floor. However, if you are installing the floor on a second story or higher, consider a thicker foam underlayment to help absorb sound. A solid cork underlayment can also be used and is extremely effective in absorbing sound.