When to Use Underlay?

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.

What happens if you don't put underlay under laminate?

If the subfloor in your home or property is uneven, then your laminate floor could move and shift if it doesn't have an underlayment for support. As a result, the floor will be more prone to wear-and-tear and could even warp.

Do you need to use underlay?

Does carpet need underlay? Yes, All carpets apart from felt-backed carpets should have underlay. Obviously budget is sometimes an issue with underlays, but it is well worth the extra money.