Do You Need Underlayment Under LVP?

A large share of LVP sold today comes with an attached pad and is designed to be installed directly on a prepared substrate with nothing else under it. For those products, adding a separate underlayment is usually prohibited. Products without an attached pad may require or allow one. Over concrete, a vapor retarder may be required whether or not there is a pad.

The decision is made by your product's installation instructions plus your project's actual requirements — not by a general preference for more cushion.

The pad is engineered as part of the plank assembly: its thickness and density are factored into how the locking system performs and how the floor sits. Stacking another underlayment underneath adds compressible depth the joints were not designed for, which can lead to joint stress, separation and lock failure over time — and will typically void the warranty.

Here the underlayment is a real decision. Your instructions will state what is acceptable — often a specific type and maximum thickness, and often with a density requirement, because an over-soft pad under rigid plank works the joints. Check whether a vapor retarder is required separately or built into the approved underlayment.

In multifamily buildings, the underlayment question is often decided by the building rather than the flooring. HOA rules and condo documents commonly set a minimum acoustic rating for hard-surface flooring and may require documentation of the assembly before installation is approved.

If that applies to you, get the building's requirement in writing first, then find a flooring product and underlayment combination that meets it and is approved by the flooring manufacturer. Reversing that order is how people end up with a floor they have to take back up.

• Locking systems are rated against a specific amount of give beneath them; extra compression works the joints.
• Soft underlayment can make a rigid plank floor feel bouncy or hollow rather than solid.
• Point loads — furniture legs, appliances — press into an over-soft assembly.
• Added thickness changes transition heights, door clearances and appliance fit.
• Unapproved layers are a common reason a warranty claim is denied.

This is the most expensive misunderstanding in the category. Underlayment is thin and compressible. It does not bridge a dip, flatten a ridge or stabilize a moving subfloor — it conforms to the surface it is laid on and passes the problem straight through to the floor above it.

Underlayment is not a substitute for correcting unacceptable floor flatness. If the substrate fails your product's flatness requirement, fix the substrate. See LVP subfloor requirements for how to check it and floor prep for the correction methods.

• Confirm whether your flooring has an attached pad.
• Read what the installation instructions permit, require and prohibit.
• Identify your substrate and whether a vapor retarder is required over it.
• Check any building, HOA or lease acoustic requirement.
• Match the allowed type, thickness and density rather than buying the thickest option.
• Confirm the finished height still works at doors, transitions and appliances.