Do I Need Underlay Under LVT Flooring on Concrete? An Honest Peterborough Fitter's Answer
Glue-down LVT needs no underlay; click LVT needs a thin, dense one. What Peterborough concrete floors need first: damp checks, levelling and costs.
Key takeaways
The short version, checked by our fitting team.
Glue-down LVT such as most Karndean and Amtico ranges never goes on underlay
Click and rigid-core LVT need a thin, high-density LVT underlay unless the plank has an approved backing
Carpet and soft laminate underlays are too spongy for LVT and can break the joints
Concrete must be moisture-tested and may need a damp-proof membrane or vapour barrier
Short answer: it depends on the type of LVT. Glue-down LVT, such as most Karndean and Amtico ranges, never goes on underlay: it is bonded straight to a smooth, dry, levelled concrete subfloor. Click-lock and rigid-core LVT usually needs a thin, high-density LVT underlay or an attached backing, and on concrete it also needs protection from rising moisture.
It is one of the questions we hear most at free home visits across Peterborough, especially in homes with concrete ground floors: new-build estates, post-war semis and extensions with a screeded floor. Getting the answer wrong is expensive. The wrong underlay can break the joints of a click floor within months, and a damp slab can lift a glue-down floor that looked perfect on the day it went down. This guide explains what we specify, and why, as a team that fits both types every week.
Do you need underlay under LVT on a concrete floor?
For glue-down LVT: no. The planks or tiles are thin and flexible, and they are designed to be stuck to a smoothed subfloor with adhesive. Putting any underlay beneath them would let the floor move, open the joints and void the manufacturer's guarantee.
For click-lock and rigid-core LVT: usually yes, unless the product already has an underlay backing attached. The underlay is not there for softness. It smooths out tiny surface irregularities, reduces footfall noise and, on concrete, often carries an integrated damp-proof layer.
The deciding factor is always the specific product's fitting instructions. Manufacturers such as Karndean, Amtico, Moduleo, Quick-Step and Polyflor each publish which underlays (if any) are approved for each range, and we follow them to the letter so your guarantee stands.
Glue-down vs click LVT on concrete: what goes underneath?
| LVT type | Underlay? | What goes on the concrete first | Best for |
|---|---|---|---|
| Glue-down LVT (e.g. Karndean, Amtico) | Never | Moisture check, damp-proof membrane if needed, smoothing compound, adhesive | Kitchens, kitchen-diners, bathrooms, herringbone and design-led layouts |
| Click-lock LVT without backing | Yes: thin, high-density LVT underlay only | Moisture check, vapour barrier or underlay with built-in damp-proof layer | Living rooms, bedrooms, hallways |
| Rigid-core LVT with attached underlay | No extra underlay (the backing is the underlay) | Moisture check and a vapour barrier where the manufacturer specifies one | Quick installs, open-plan rooms, slightly imperfect subfloors |
| Rigid-core LVT without backing | Yes: the manufacturer's approved underlay | Moisture check, vapour barrier or combined underlay | Larger rooms and areas that need a little extra acoustic help |
You can see the full range we supply and fit on our luxury vinyl tiles Peterborough page, and the glue-down ranges in more detail on our Karndean flooring Peterborough and Amtico flooring Peterborough pages.
Why can't I use carpet or laminate underlay under LVT?
Because it is far too soft. Carpet underlay is designed to compress, and most foam laminate underlays are thicker and spongier than LVT can tolerate. Click LVT is thinner than laminate and relies on its locking joints staying rigid. On a soft base the joints flex every time someone walks across them, and over time they peak, gap or snap.
Proper LVT underlay is thin (often around 1–1.5mm) and dense, so it supports the joint instead of letting it sink. If you have spare underlay left over from a carpet or laminate job, please do not use it under LVT. It is one of the most common reasons we are called out to failed DIY floors.
The same rule applies to stacking: never put an extra underlay under a rigid-core plank that already has a backing attached. Two layers make the floor bounce, and most manufacturers rule it out in their guarantee terms.
Does concrete need a damp-proof membrane under LVT?
Often, yes. Concrete holds moisture long after it looks dry, and older slabs in Peterborough's 1930s to 1960s housing may have a failed or missing damp-proof course in the floor. Moisture rising through the slab can break down adhesive under glue-down LVT and cause mould or swelling beneath a click floor.
That is why we test the subfloor moisture level at the survey before we recommend anything. Depending on the reading and the product:
- Glue-down LVT may need a liquid damp-proof membrane applied to the concrete before the smoothing compound goes on.
- Click LVT typically goes on a polythene vapour barrier, or on an LVT underlay with a damp-proof layer built in.
- New screed (in an extension or new build) must be fully dried out before any LVT goes down. We will tell you honestly if it is not ready yet.
If you already suspect a damp problem, read our guide to fitting LVT on a floor with damp issues first.
Is the concrete flat enough for LVT?
LVT shows everything underneath it. A ridge of old adhesive, a dip near a doorway or a crack in the slab will telegraph through, especially on glue-down floors with a sheen. For glue-down LVT we almost always apply a smoothing (levelling) compound over the concrete, so the adhesive has a perfectly flat, absorbent surface to bond to.
Click and rigid-core LVT are more forgiving of small imperfections, but they still need a flat base. Humps and hollows over the manufacturer's tolerance must be ground or filled first, and an underlay cannot hide them.
How much does LVT on concrete cost in Peterborough?
All our prices are supply and fit. From our flooring prices Peterborough page:
| Item | Price (supply and fit) |
|---|---|
| LVT | From £35/m² |
| Mid-range click-lock and rigid-core LVT | £35–£50/m² |
| Premium glue-down Karndean and Amtico | £50–£70+/m² |
| Subfloor levelling (where needed) | £5–£15/m² |
| Typical hallway and kitchen-diner (25–35 m²) | £900–£2,400 |
As a worked example, a 20 m² kitchen-diner in mid-range rigid-core LVT would be 20 × £35–£50 = £700–£1,000. If that concrete floor also needed levelling, add 20 × £5–£15 = £100–£300. Any LVT underlay, vapour barrier or damp-proof membrane is itemised in the written quote, so you can see exactly what your floor needs and why.
Which is better on concrete: glue-down or click LVT?
Both work well when the subfloor is right. Glue-down is our usual recommendation for kitchens, bathrooms and anywhere with underfloor heating, because it is bonded flat, feels solid underfoot and adds very little thermal resistance. Click LVT suits living rooms and bedrooms where a slightly quicker install is useful and the floor is already in good condition. For a deeper look, see our click-lock vs glue-down LVT guide.
If you are still deciding between materials altogether, our wider flooring Peterborough hub compares LVT with sheet vinyl, laminate and engineered wood, and our vinyl flooring Peterborough page covers the budget-friendly sheet option.
What we check at your free home visit
- Whether the floor is a concrete slab, a screed or a timber floor (the answer changes the whole specification)
- A moisture reading on the concrete
- Flatness, cracks, old adhesive and any height changes at doorways
- Whether there is underfloor heating, and what type
- Which LVT you like, and which underlay or preparation that exact product requires
We visit homes across Peterborough, from Hampton and Paston Reserve to Werrington, Orton and Stanground, as well as the wider PE postcodes and Cambridgeshire. See our carpets and flooring in Peterborough page for local coverage.
Not sure what is under your current floor? Call our Peterborough team on 01733 924009 to book a free home visit, Monday to Friday, 9am–5pm. We will bring samples, test the subfloor and send a written quote within 24 hours, fitted by our own team and backed by a 2-year workmanship guarantee.
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Book a free home measurementDo I need underlay under Karndean on concrete?
No. Karndean glue-down LVT is bonded directly to a smoothed, dry concrete subfloor with adhesive. Underlay would let it move and void the guarantee. Karndean's click and rigid-core ranges are different: follow the specific range's underlay guidance, which we check at the survey.
Can I put LVT straight onto concrete without anything underneath?
Not quite. Glue-down LVT needs a moisture check, often a smoothing compound and adhesive. Click LVT needs a vapour barrier or a suitable LVT underlay unless the plank has an approved backing. Laying any LVT loose onto bare, untested concrete risks damp and joint failure.
Can I use laminate underlay under click LVT?
Generally no. Most laminate underlays are too soft and thick for LVT, so the locking joints flex and can break. Use a thin, high-density underlay that the LVT manufacturer approves for that product.
What thickness of underlay is best for LVT on concrete?
Thin and dense, often around 1–1.5mm, ideally with a built-in damp-proof layer on concrete. Thicker is not better with LVT. Always check the maximum the manufacturer allows for your range.
Does rigid-core LVT with attached underlay need a damp-proof membrane on concrete?
Often it does. Many attached backings are acoustic rather than moisture barriers, so manufacturers may still require a polythene vapour barrier on concrete. We test the slab and follow the product's instructions.
Is there an LVT fitter near me in Peterborough who can check my concrete floor?
Yes. We fit LVT across Peterborough and the PE postcodes from our showroom at The Manor Grove Centre, PE1 5UH. Call 01733 924009 to book a free home visit with samples and a subfloor check, Monday to Friday.
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