Underlayment for laminate and vinyl: types, vapor barriers and coverage
By Michał Białas · Last updated
Floating laminate and click vinyl need an underlayment unless the planks have a pad attached. Choose by floor type first — vinyl needs a thin, dense one — then by subfloor: over concrete you need a vapor barrier, either built into the underlayment or as a separate sheet. Buy the floor area plus about 5%, rounded to whole rolls.
What underlayment does
Under a floating floor, the underlayment cushions small irregularities in the subfloor, reduces the hollow sound of footsteps, and, in some products, blocks moisture from below. It does not fix an uneven floor: anything beyond what the installation guide allows has to be leveled first.
Types compared
| Type | Typical thickness | Built-in vapor barrier | Radiant heat | Best for |
|---|---|---|---|---|
| Foam | About 2 mm | Some versions | Usually fine | Budget laminate |
| Foam with vapor barrier (“2-in-1”, “3-in-1”) | 2–3 mm | Yes | Usually fine | Laminate over concrete |
| Felt | About 3 mm | Often | Usually fine | Quieter laminate and engineered wood |
| High-density acoustic | About 2 mm | Often | Good | Apartments, upper floors |
| Cork | 2–6 mm | No | Thin only | Sound reduction, natural material |
| Rubber | About 3 mm | Sometimes | Usually fine | Sound reduction |
| XPS or wood fiber boards | 3–7 mm | No | Usually not | Bridging small dips under laminate |
| Vinyl / SPC underlayment | 1–1.5 mm, dense | Some versions | Good | Click vinyl without an attached pad |
Values are typical; the product’s own data decides. Two rules matter most: vinyl planks need a thin, firm underlayment because soft foam lets the click joints flex and break, and thick insulating boards or cork work against radiant floor heating.
Vapor barrier: built in or separate
Concrete slabs and screeds release moisture for a long time. Over them, floating floors need a vapor barrier — polyethylene sheeting, often 6 mil in the US and 0.2 mm in Europe — with about 8 in (200 mm) overlaps, taped seams and about 2 in (50 mm) turned up the walls. That is why the calculator adds 15% to the barrier area, plus seam tape of area ÷ roll width + perimeter. If the underlayment has a built-in barrier, the separate sheet and its tape drop off the list.
Over a wooden subfloor, a vapor barrier is usually not wanted, because it can trap moisture in the wood. Follow the flooring maker’s instructions.
Sound: what underlayment can and can’t do
There are two kinds of noise. Walking noise in the room itself — the hollow click of a floating floor — is reduced by denser underlayments such as high-density acoustic types, felt and rubber. Impact noise heard in the room below matters most in apartments, where building rules or the owners’ association may require a minimum rating. If that applies, choose an underlayment whose data sheet states the required rating for your type of floor, and keep the receipt.
Thicker is not automatically quieter. A thick, soft foam can make a floating floor sound worse by letting it bounce, and it strains the click joints.
Worked examples
Example 1 (feet): 15 × 12 ft laminate floor on concrete
- Area 180 sq ft; underlayment with 5%: 189 sq ft.
- Plain 2 mm foam in 100 sq ft rolls: 2 rolls. Plus a separate vapor barrier: 207 sq ft → one 250 sq ft roll, and one roll of seam tape.
- 3-in-1 foam with vapor barrier (100 and 200 sq ft rolls): one 200 sq ft roll — and no separate sheet or tape.
- Felt with vapor barrier: two 100 sq ft rolls, no separate sheet.
Example 2 (meters): 5.0 × 3.6 m laminate floor on screed
- Area 18 m²; underlayment with 5%: 18.9 m².
- Foam 2 mm in 10 or 15 m² rolls: two 10 m² rolls. Separate PE barrier 20.7 m² → two 20 m² rolls, plus a 50 m roll of tape.
- Foam with vapor barrier: two 10 m² rolls, no separate barrier.
- Wood fiber boards in 7 m² packs: 3 packs — and, if the screed has radiant heating, a warning, because 5 mm fiber board insulates too much.
Installation checklist
- Check the subfloor is dry, clean and within the flatness tolerance of the flooring.
- On concrete, lay the vapor barrier first (or use an underlayment with one built in), overlapped and taped.
- Roll the underlayment out at right angles to the planks, or as the product says; butt the seams, don’t overlap them, unless it has an overlap lip.
- Tape the seams if the product calls for it.
- Cut the underlayment to the wall; the baseboard covers the expansion gap, not the underlayment.
In the laminate calculator and vinyl calculator, the Underlayment selector shows only the types that suit the plank type, in the sizes sold in your market. For the rest of the list, see laminate vs. vinyl plank.
Frequently asked questions
Do I need underlayment if my planks have a pad attached?
No. Choose “attached to the planks” and no underlayment is added. Over concrete you may still need a vapor barrier unless the attached pad includes one.
Can I double up underlayment for more cushion?
No. Two layers make the floor bounce and stress the click joints. Use one underlayment of the type the flooring maker allows.
Which underlayment is best over radiant heat?
A thin, dense one with low thermal resistance that the maker rates for radiant heat. Avoid thick boards and cork.
How much underlayment should I buy?
The floor area plus about 5%, rounded up to whole rolls or packs. Rolls are commonly 100 or 200 sq ft in the US and 10 or 15 m² in Europe.