Quick Answer
Most modern luxury vinyl plank already has attached IXPE or cork underlayment on the back, so you do not need a separate pad. The one exception that catches people out: any slab installation still needs a 6 mil polyethylene vapour barrier under the plank, even if the plank has attached pad.
On a wood subfloor with planks that have attached pad, install bare. Adding a second pad voids the warranty.
The Decision Tree
- Plank has attached pad + wood subfloor: install bare. No underlayment.
- Plank has attached pad + concrete slab: 6 mil poly vapour barrier under, plank on top.
- Plank has NO attached pad + wood subfloor: 1 mm to 1.5 mm vinyl-specific underlayment.
- Plank has NO attached pad + concrete slab: 3-in-1 underlayment with vapour barrier.
- Glue-down LVT: no underlayment ever; it bonds direct to substrate.
Why Not Just Add a Pad Anyway?
Three reasons not to layer pad under attached-pad plank:
- Warranty void. Almost every major brand explicitly forbids it.
- Click joints fail. Too much cushion makes the plank flex with foot traffic and pops joints apart.
- Indentation. Furniture loads punch through a softer floor and leave permanent dents.
What Counts as a "Vapour Barrier"
A 6 mil clear polyethylene sheet, overlapped 8 inches at seams, taped, run up the wall 2 inches behind the baseboard. That is the cheapest, fastest, most foolproof slab moisture barrier. Total cost: under $30 for a typical room.
What Happens If You Skip Underlayment
On a wood subfloor with attached-pad plank, nothing bad happens, that is exactly the install the manufacturer wants. On a slab with no vapour barrier, you risk silent moisture migration that slowly degrades the click joints from below. You might not notice for two or three years until planks start to lift or release a musty smell.
On a wood subfloor with bare-back plank, skipping the thin pad leaves you with a louder, harder floor that telegraphs every subfloor screw and seam. The plank will still hold up, but it will feel cheap underfoot and click joints can wear faster from subfloor irregularities.
The TL;DR: attached pad on wood = no extra needed. Slab = always 6 mil poly minimum. Bare-back plank on wood = thin vinyl-specific pad. Glue-down LVT = no pad ever.
Real-World Notes
Field experience matters more than spec sheets here. Installers who do this work week-in week-out will tell you the same things: the substrate is everything, the acclimation step is non-optional, and a single missed prep detail will show up six months later when the seasons change.
Climate also plays a bigger role than most homeowners expect. A floor that performs perfectly in coastal Florida might cup in dry Denver winters. Match the product to the climate zone, and your warranty terms to your actual indoor humidity range.
Insurance and resale considerations are worth a mention too. Document the install with photos, keep the receipts, and save the lot numbers. Future buyers ask, and future repairs need them. Whether vinyl plank flooring needs underlayment is a long-term decision, treat it like one.
One last note from the trade: cheap is rarely cheap. The lowest-priced product on the shelf usually has the thinnest wear layer, the loosest click, and the worst warranty terms. A mid-priced product from a known brand will outlast the budget option by 50 percent or more on average, which works out cheaper per year of service.
Frequently Asked Questions
Does the answer change for rental properties?
The general guidance holds, but landlords usually optimise for durability over aesthetics, so they lean to the cheapest waterproof option that will survive turnover after turnover.
What about radiant heat?
Always confirm your flooring choice is rated for radiant heat (most rigid-core LVP is, solid hardwood usually is not). Manufacturers publish a maximum subfloor temperature, typically 82°F (28°C).
How long should I let the materials sit before installing?
48 hours in the room of installation is the safe default for laminate and LVP. Engineered hardwood needs longer, often 7 to 14 days, until its moisture content is within 2 to 4 percent of the subfloor.
Does the same answer apply in the UK?
Mostly yes. UK retailers like B&Q, Wickes and Carpetright sell the same product categories with similar specs, though pricing and brand names differ.
Pro Tips From the Trade
- Buy 10 percent extra. You will cut waste at every wall and inside every doorway. Pros budget 10 percent overage on rectangular rooms and 15 percent on rooms with diagonals or lots of cutouts.
- Keep a few planks aside. Future repairs need a colour and lot match. Stash at least one full carton in the garage or basement, ideally from the same production run.
- Photograph the install. Snap pictures of the subfloor, vapour barrier, expansion gaps, and any transitions before the baseboards go on. Warranty claims often hinge on documentation.
- Save the receipts and lot numbers. Almost every flooring warranty requires proof of purchase and the production lot to be honoured.
Bottom Line
Flooring decisions sit at the intersection of budget, lifestyle and resale value. Get the prep right (flat, dry, clean subfloor; correct underlayment; proper acclimation) and even a mid-priced product will look and perform like a premium one. Cut corners on prep and even the most expensive plank will telegraph every flaw underneath.
