Getting the underlayment right is one of the most important steps when installing vinyl flooring. The wrong choice (or skipping it entirely) can lead to moisture damage, noise issues, uneven surfaces, and a floor that fails prematurely.
This guide covers everything you need to know about what to put under vinyl flooring, including the best underlay materials for different subfloors, rooms, and budgets.
Why Does Vinyl Flooring Need Underlay?
Vinyl is a thin, flexible material that conforms closely to whatever is beneath it. Unlike thicker flooring types, every imperfection in the subfloor will telegraph through to the surface. Underlay serves several critical functions:
- Moisture protection prevents water vapour from the subfloor damaging the vinyl from below, which can cause warping, bubbling, and mould growth
- Surface smoothing creates a flat, even base so minor subfloor imperfections do not show through
- Sound reduction dampens footstep noise and impact sound, particularly important in flats and upper-storey rooms
- Thermal insulation adds a layer of warmth, making the floor more comfortable underfoot during colder months
- Cushioning provides a slightly softer feel, reducing fatigue when standing for long periods
Important note: Not all vinyl flooring needs separate underlay. Many luxury vinyl tiles (LVT) and click vinyl planks come with an integrated backing layer. Always check the manufacturer’s guidance before adding extra underlay, as too much cushioning can cause click-lock joints to separate.
Best Underlay Materials for Vinyl Flooring
Each underlay material has different strengths. The right choice depends on your subfloor type, the room, and your priorities (moisture protection, soundproofing, warmth, or budget).
1. Foam Underlay
Foam is the most popular and affordable underlay for vinyl flooring. Lightweight and easy to install, it provides basic cushioning, sound reduction, and thermal insulation.
Best for: General rooms, bedrooms, living areas on dry subfloors
- Lightweight and simple to cut and lay
- Available with built-in vapour barrier for concrete subfloors
- Good sound dampening for upper-storey installations
- Very affordable (typically under £2/m2)
Limitations: Thinner options offer minimal cushioning. Not suitable for very uneven subfloors. Choose a maximum 2mm thickness for click vinyl to avoid joint stress.
2. Cork Underlay
Cork is a premium natural underlay that excels in thermal insulation and sound absorption. Its cellular structure traps air, making it one of the warmest options available.
Best for: Living rooms, bedrooms, home offices where warmth and quiet are priorities
- Excellent thermal insulation (high tog rating)
- Superior sound absorption, both impact and airborne noise
- Naturally antimicrobial and hypoallergenic
- Sustainable and eco-friendly (harvested from bark without felling trees)
- Long lifespan without compression
Limitations: More expensive than foam. Requires a separate vapour barrier on concrete subfloors unless the product includes one.
3. Rubber Underlay
Rubber underlay offers the best soundproofing performance of any underlay type. Dense and resilient, it absorbs both impact noise and airborne sound effectively.
Best for: Flats, apartments, upper floors, rooms above living spaces, children’s rooms
- Outstanding noise reduction (often the highest dB rating)
- Durable and resists compression over time
- Provides comfortable cushioning underfoot
- Naturally moisture-resistant
Limitations: Heavier and more difficult to handle. Higher cost. Can have a slight smell initially (dissipates within days).
4. Plywood Underlay
Plywood is used as a structural underlay to create a perfectly smooth, rigid surface for vinyl. It is a levelling solution rather than a cushioning or insulating layer.
Best for: Uneven timber subfloors, old floorboards with gaps or ridges, glue-down vinyl installations
- Creates a completely flat surface for thin vinyl to lie on
- Adds structural stability to bouncy or uneven floors
- Essential for glue-down vinyl where surface flatness is critical
- Widely available and relatively affordable
Limitations: No moisture barrier (needs a separate DPM on concrete). No sound insulation. Adds floor height (typically 5-6mm). Requires screwing down properly to avoid squeaks.
5. Self-Levelling Compound
For concrete subfloors with dips, bumps, or unevenness, self-levelling compound is used to create a perfectly flat surface before laying vinyl. It is poured as a liquid and sets to a smooth, hard finish.
Best for: Uneven concrete subfloors, renovations, converting garages or basements
- Fills dips and levels bumps in one application
- Sets quickly (walkable within hours)
- Provides a perfect surface for any vinyl type
Limitations: Requires a clean, primed surface. Not suitable over floorboards (use plywood instead). Adds drying time to your project.
6. Felt Underlay
Felt underlay is made from compressed recycled fibres. It provides good sound absorption, a smooth surface, and moderate thermal insulation.
Best for: Eco-conscious installations, rooms where sound reduction is needed on a moderate budget
- Made from recycled materials (environmentally friendly)
- Good sound dampening properties
- Creates a smooth surface for vinyl
- Moderate thermal insulation
Limitations: Can absorb moisture if not paired with a vapour barrier. Slightly more expensive than basic foam.
7. Damp-Proof Membrane (DPM)
A DPM is not strictly an underlay but is essential on any concrete subfloor to prevent rising moisture from damaging your vinyl. It is a thin polyethylene sheet laid before the underlay and flooring.
Best for: All concrete subfloors, ground-floor installations, basements
- Prevents moisture vapour from reaching the vinyl
- Inexpensive and simple to install (overlap sheets by 200mm and tape joints)
- Essential for warranty compliance on most vinyl products
Limitations: Provides no cushioning, sound, or thermal benefits. Must be used alongside a separate underlay for those functions.
Choosing Underlay Based on Your Subfloor
Your existing subfloor is the biggest factor in deciding what to put under vinyl flooring. Here is a quick guide:
Concrete Subfloor
- Essential: Damp-proof membrane (DPM) or underlay with integrated vapour barrier
- If uneven: Self-levelling compound first, then DPM and underlay
- Best underlay options: Foam with vapour barrier, cork with DPM, or rubber
- Always do a moisture test before installation (tape a plastic sheet to the floor for 48 hours and check for condensation)
Timber/Wooden Subfloor
- If smooth and level: Foam or felt underlay is sufficient
- If uneven or gappy: Lay 5-6mm plywood over the boards first, then underlay
- No DPM needed (timber subfloors allow moisture to escape naturally)
- Screw down any loose boards to prevent squeaking before installation
Existing Vinyl or Tile
- If flat and well-adhered: You can often lay directly over existing vinyl with a thin foam underlay
- If damaged or lifting: Remove the old flooring first
- Laying over existing tile is possible if grout lines are shallow; use a levelling compound for deep grout joints
What to Put Under Vinyl Flooring by Room
Different rooms have different demands. Here is what works best in each space:
Bathroom and Kitchen
These are the highest-moisture rooms in any home. Your underlay must prioritise waterproofing above all else.
- Use underlay with an integrated moisture barrier or a separate DPM
- Avoid cork and felt (which can absorb water) unless the product is specifically rated as waterproof
- Foam with a built-in vapour barrier is a practical, affordable choice
- Ensure all seams are sealed with waterproof tape
- For bathroom vinyl installations, silicone sealant around edges provides extra protection
Bedroom and Living Room
Comfort and warmth are the priorities here. Moisture is less of a concern (unless ground floor on concrete).
- Cork underlay provides the best combination of warmth, comfort, and sound reduction
- Foam underlay is a budget-friendly alternative with decent performance
- On concrete ground floors, always include a vapour barrier
Hallway and High-Traffic Areas
Durability and a stable surface matter most in hallways where heavy foot traffic can wear down softer underlays.
- Dense foam or rubber underlay resists compression over time
- Avoid overly thick or soft underlays that may cause the vinyl to flex excessively
- Plywood over timber subfloors creates a rigid, stable base
Flats and Upper Floors
Sound insulation is critical to avoid disturbing neighbours below.
- Rubber underlay offers the best acoustic performance
- Check your building’s requirements: many leasehold flats mandate a minimum sound reduction rating
- Look for underlay with tested dB ratings (19dB+ is ideal for flats)
- Learn more in our floor soundproofing guide
Quick Comparison Table
| Underlay Type | Moisture Protection | Sound Reduction | Thermal Insulation | Cost | Best For |
|---|---|---|---|---|---|
| Foam | Good (with barrier) | Moderate | Moderate | Low | General use, budget |
| Cork | Low (needs DPM) | High | High | Medium-High | Warmth, comfort |
| Rubber | High | Excellent | Moderate | High | Flats, soundproofing |
| Plywood | None | None | Low | Medium | Levelling timber floors |
| Felt | Low (needs DPM) | Good | Moderate | Medium | Eco-friendly installs |
| Self-Levelling | None | None | None | Medium | Uneven concrete |
| DPM | Excellent | None | None | Very Low | All concrete subfloors |
Common Mistakes to Avoid
These are the errors we see most often with vinyl underlay installations:
- Using underlay that is too thick: Click vinyl systems are designed for firm, thin underlays (1-2mm max). Thick underlay causes joints to flex and separate over time
- Doubling up underlays: If your vinyl has an integrated backing, do not add another underlay on top. This creates too much give and voids the warranty
- Skipping the DPM on concrete: Even dry-looking concrete releases moisture vapour. Without a DPM, this moisture gets trapped under the vinyl and causes bubbling or mould
- Not levelling the subfloor first: Underlay can smooth minor imperfections but cannot fix significant dips or bumps. Level the floor properly before laying anything
- Overlapping underlay sheets incorrectly: Butt foam sheets edge-to-edge (not overlapping) and tape joints. Overlapping creates raised ridges that show through thin vinyl
Do You Always Need Underlay for Vinyl Flooring?
Not always. Here are the situations where you may not need separate underlay:
- LVT with integrated backing: Many premium click-LVT products (like Karndean, Amtico, and Luvanto) have a factory-attached underlay. Adding more is unnecessary and can cause problems
- Glue-down vinyl: This type must bond directly to the subfloor. Underlay prevents adhesion. You still need a smooth, level surface (plywood or levelling compound) and a DPM on concrete
- Loose-lay vinyl: Some heavy loose-lay products grip the subfloor with friction and do not require underlay
Always check your vinyl manufacturer’s installation guide. Using incorrect underlay can void your product warranty.
Frequently Asked Questions
Can I put vinyl flooring directly on concrete without underlay?
You can for glue-down vinyl, but you must still use a damp-proof membrane (DPM) to protect against moisture vapour. For click vinyl, underlay is recommended to provide cushioning and sound reduction. Never install any vinyl on concrete without addressing moisture first.
What is the best underlay for vinyl flooring in a bathroom?
A thin foam underlay with an integrated moisture barrier works best in bathrooms. Avoid cork or felt underlays that can absorb water. Ensure all underlay seams are taped with waterproof tape, and apply silicone sealant around the perimeter for extra moisture protection.
Can I use carpet underlay under vinyl flooring?
No. Carpet underlay is far too thick and soft for vinyl flooring. It will cause click-lock joints to separate, create an unstable surface, and void your vinyl warranty. Always use underlay specifically designed for hard flooring (typically 1-2mm thickness for click vinyl).
Do I need underlay if my vinyl already has a backing layer?
If your vinyl has a factory-integrated backing (common with premium LVT), you do not need additional underlay. Adding extra cushioning can cause the joints to flex and fail. You may still need a DPM on concrete subfloors, but check the product specifications as some integrated backings include moisture protection.
How thick should underlay be for vinyl click flooring?
Most vinyl click flooring manufacturers recommend a maximum underlay thickness of 1-2mm. Thicker underlay creates too much give, which puts stress on the click joints and causes them to separate over time. Always follow the flooring manufacturer’s specific recommendation.
What causes vinyl flooring to bubble after installation?
Bubbling is almost always caused by trapped moisture rising from the subfloor. This happens when a DPM is not used on concrete, when underlay seams are not sealed, or when the subfloor was not dry enough at the time of installation. Fixing this usually requires lifting the affected area and addressing the moisture source.
Final Thoughts
Choosing the right underlay for vinyl flooring is straightforward once you know your subfloor type and room requirements. On concrete, always use a DPM. In flats, prioritise soundproofing. In living areas, aim for warmth and comfort. And always check whether your vinyl already has integrated backing before adding more.
If you are unsure which underlay suits your project, or you want expert advice on installing vinyl click flooring, visit TEKA Flooring in Peterborough. Our team can recommend the right products and provide professional fitting services to ensure your vinyl floor performs perfectly for years to come.
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