Underlay for Vinyl Flooring: Do You Need It? – Goodrich

Underlay for vinyl flooring is a topic that generates considerable confusion among Singapore homeowners and even some contractors. Unlike laminate or engineered timber, where underlay is virtually mandatory, vinyl flooring has a more nuanced relationship with underlayment. The answer to whether you need it depends on the type of vinyl, your subfloor condition, and the specific performance goals of your installation.

This guide clarifies when underlay is beneficial, when it is unnecessary, and which types work best with different vinyl flooring products.

What Does Underlay Actually Do?

Before deciding whether your vinyl flooring needs underlay, it helps to understand the functions that underlayment serves in a flooring system.

• Sound reduction: Underlay absorbs impact sound (footsteps, dropped objects) and reduces sound transmission to rooms below. This is particularly relevant in Singapore’s multi-storey HDB flats and condominiums, where noise complaints between neighbours are common.
• Subfloor imperfection smoothing: A thin underlay layer can bridge minor imperfections in the subfloor — small bumps, shallow depressions, and hairline cracks — preventing them from telegraphing through the vinyl surface.
• Thermal insulation: Underlay provides a modest layer of thermal insulation, making the floor feel warmer underfoot. In Singapore’s consistently air-conditioned interiors, this can add comfort, particularly in bedrooms.
• Moisture barrier: Some underlays incorporate a moisture-resistant membrane that protects the flooring from residual moisture in concrete subfloors — a common concern in Singapore’s humid climate.
• Cushioning: Additional underfoot cushioning improves comfort for standing and walking, reducing fatigue in residential and commercial settings.

When You Need Underlay

Several scenarios make underlay a worthwhile or necessary addition to your vinyl flooring installation.

Click-Lock SPC and Rigid Core Vinyl

Rigid-core vinyl products — including SPC (stone polymer composite) and WPC (wood polymer composite) — installed using a click-lock floating system often benefit from underlay. Because the floor floats over the subfloor rather than being glued down, a thin underlay layer (typically 1mm to 1.5mm) improves acoustic performance, provides minor cushioning, and helps the planks settle evenly over the substrate.

Many SPC products now come with an attached underlay — a thin foam or cork layer pre-bonded to the underside of each plank. If your chosen product already has this integrated backing, additional separate underlay is generally unnecessary and may even compromise the floor’s stability.

Concrete Subfloors in HDB and Condo Units

Singapore’s HDB flats and condominiums typically have concrete subfloors that can transmit impact noise between units. For floating vinyl installations on concrete, underlay with sound-reduction properties helps meet the acoustic expectations of both residents and neighbours. Some condominiums have specific acoustic rating requirements in their by-laws, and underlay may be needed to achieve compliance.

Uneven Subfloors

Older HDB resale flats and landed properties sometimes have subfloor surfaces that are not perfectly level. While significant irregularities should be corrected with self-levelling compound or screeding, minor imperfections of 1mm to 2mm can be accommodated by a quality underlay. This saves the time and cost of extensive subfloor preparation.

When You Do Not Need Underlay

There are clear situations where underlay is unnecessary — and where adding it could actually cause problems.

Glue-Down LVT Installation

When luxury vinyl tiles are adhered directly to the subfloor with pressure-sensitive or permanent adhesive, underlay must not be used. The adhesive needs direct contact with both the vinyl and the subfloor to create a secure bond. Placing underlay between them would prevent proper adhesion and could cause the flooring to shift, bubble, or delaminate.

Glue-down LVT relies on the subfloor itself for stability, and the adhesive layer provides a degree of sound dampening. For this installation method, thorough subfloor preparation — cleaning, levelling, and priming — is the key to a successful result.

Vinyl with Pre-Attached Backing

As mentioned, many modern vinyl flooring products include a factory-attached underlay layer. Adding separate underlay beneath these products creates an excessively soft, unstable base that can cause the click-lock joints to flex and eventually fail. Always check the manufacturer’s installation instructions — if the product has integrated backing, additional underlay is typically prohibited.

Vinyl Sheet Flooring

Vinyl sheet (roll) flooring is designed to be fully adhered to a smooth, prepared subfloor. Like glue-down LVT, it does not use underlay. The continuous adhesive bond provides the stability and performance characteristics the product requires.

Types of Underlay for Vinyl Flooring

When underlay is appropriate, selecting the right type ensures optimal performance without compromising the vinyl flooring above.

Underlay Type	Thickness	Best For	Key Properties
IXPE foam	1-1.5mm	SPC floating floors	Moisture-resistant, thin, stable
Cork	1.5-2mm	Acoustic performance	Excellent sound reduction, natural
Rubber	1-2mm	Commercial vinyl	Dense, durable, sound-absorbing
PE foam with barrier	1-2mm	Concrete subfloors	Moisture protection, affordable

Critical rule: Never use underlay thicker than 2mm under vinyl flooring. Excessive thickness creates a spongy surface that stresses click-lock joints and can cause premature failure. Unlike laminate or engineered timber, vinyl flooring requires a firm, stable base.

Installation Tips for Singapore Conditions

Singapore’s climate and building conditions create specific considerations when installing underlay with vinyl flooring products.

Moisture testing: Before installing any floating vinyl system, test the concrete subfloor for moisture. Singapore’s humidity means that ground-floor units and newly screeded floors can retain significant moisture. A simple plastic sheet test — taping a one-metre square of polyethylene to the floor and checking for condensation after 48 hours — provides a basic indication. If moisture is present, use an underlay with an integrated moisture barrier or install a separate damp-proof membrane.

Acclimatisation: Allow both the vinyl flooring and the underlay to acclimatise in the installation room for at least 48 hours before fitting. This allows the materials to adjust to the ambient temperature and humidity, reducing the risk of dimensional movement after installation.

Seam taping: Underlay sheets should be laid with edges butted together — not overlapping — and sealed with adhesive tape along the seams. Overlapping creates a ridge that will telegraph through the vinyl surface, and gaps allow moisture to bypass the barrier.

Expansion gaps: Floating vinyl installations require an expansion gap of 5mm to 8mm around the perimeter and at any fixed objects (columns, door frames, pipes). The underlay should extend to the wall, but the vinyl should stop short to allow for natural expansion and contraction.

Final Thoughts

Whether you need underlay for vinyl flooring depends entirely on your product type, installation method, and subfloor conditions. For floating SPC installations in Singapore’s HDB flats and condos, a thin, appropriate underlay improves acoustics and comfort. For glue-down LVT and vinyl sheet, skip the underlay entirely and invest in proper subfloor preparation instead.

Book an appointment with our design consultants to discuss the best vinyl flooring and underlay combination for your home.