Short answer: almost always yes
Underlayment goes between subfloor and floating laminate. It cushions, reduces noise, smooths minor subfloor texture, and often provides the required vapor barrier on concrete.
Skipping underlay voids many warranties and makes floors loud and hollow-sounding.
Types of underlay
Never stack two soft underlays unless the manufacturer explicitly permits it — too much flex breaks click locks.
- Foam (basic): 2–3 mm, budget rooms, smooth plywood subfloor
- Foam + vapor barrier (combo roll): required on concrete slabs in most regions
- Felt / fiber: denser, better sound — good for condos and second floors
- Cork: natural sound dampening, moderate moisture resistance
- Attached pad on plank: some laminates include factory pad — no second layer unless spec allows
Concrete vs wood subfloor
On concrete: use underlay with built-in 6 mil vapor barrier or separate poly sheet per local code. Test slab moisture first.
On plywood: standard foam or felt; vapor barrier usually not needed unless over crawl space with humidity.
Roll coverage math
Underlay rolls list sq ft coverage — usually 100–200 sq ft. Total room sq ft + 10% overlap at seams, round up one roll. Example: 450 sq ft project with 100 sq ft rolls → buy 5 rolls. Underlay is not included in box count — budget separately.