Impact sound insulation for vinyl – Which vinyl flooring underlay should you choose?

by André Maack 26.04.2023

ca. 18 Min. 0
26.04.2023

Many people pay too little attention to impact sound insulation for vinyl, thinking that the underlay will not be visible once the floor is laid anyway. Yet choosing the right vinyl flooring underlay plays an important role. Buyers of vinyl flooring often wonder whether an underlay is actually necessary.

And if it is, which impact sound underlay should be used for the chosen vinyl flooring? The differences between vinyl flooring underlays are not always obvious. Finding the right vinyl flooring underlay is not difficult. Here you will find the most important information about impact sound underlays for vinyl flooring.

Looking for the right underlay for your vinyl flooring? Discover our range of underlays for vinyl flooring and choose the right solution for a suitable and secure floor build-up.

What types of vinyl flooring underlay are available?

For a clearer overview, we list the most important types of vinyl flooring underlay available on the market. Specific recommendations from individual manufacturers for particular vinyl underlays are not covered here. Always check the installation instructions to see whether a particular underlay must be used. The manufacturer’s approval is crucial for the correct floor build-up. Following the installation requirements may also be a condition of a voluntary manufacturer’s guarantee; your statutory rights remain separate from this.

Not every impact sound underlay is equally suitable for vinyl. General judgements about materials matter less than the approval for the specific vinyl flooring and the technical properties of the underlay.

How to find the right underlay:

• First check which type of vinyl flooring you are installing and whether an underlay is already integrated.
• Check the installation instructions to see which underlays the manufacturer approves or expressly excludes.
• Take the subfloor and any required moisture protection into account.
• For click vinyl, make sure the underlay has sufficient compressive strength.
• With underfloor heating, the thermal resistance of the entire floor build-up must also be considered.

The main types of vinyl flooring underlay at a glance

High-density PU foam:
In addition to polyurethane, it also contains mineral fillers. Depending on the product, underlays made from this material can achieve very low thermal resistance and high compressive strength. For click vinyl, however, the specific manufacturer approval and the stated technical values are always decisive.
There are three types of high-density PU foam impact sound underlay for vinyl:

• Decoupling impact sound underlay for vinyl: for click vinyl, provided the manufacturer approves a separate underlay. A compression-resistant underlay helps support the click joint.
• Grip underlay for vinyl: underlay with an anti-slip effect for approved floating floors, for example wineo Purline click flooring or wineo design click flooring. The gripping surface holds the flooring in place; other manufacturers may also specify such systems for their vinyl flooring.
• Self-adhesive impact sound underlay for vinyl: a special dry-adhesive underlay for glue-down vinyl and design flooring planks. It enables floating installation with one-sided fixing and, depending on the product and installation situation, can replace traditional wet-bed bonding.

We can send you suitable samples of these options on request. We offer a free sample service. Simply select the relevant sample here:

• planeo SilentStick - Self-adhesive impact sound underlay

Polystyrene/XPS underlays:
Polystyrene is not inherently unsuitable for vinyl. XPS underlays developed specifically for LVT, SPC and rigid flooring can provide sufficient compressive strength and may also be suitable for underfloor heating. The specific product approval, CS value and thermal resistance are decisive.

Latex underlay:
The construction and technical properties of commercially available latex underlays vary considerably. Only use this type of underlay if it is expressly approved for your vinyl flooring.

Cork:
Some manufacturers also offer cork underlays for certain vinyl or design floors. As a natural product, cork is available in different qualities. Whether an underlay is suitable for click vinyl or underfloor heating therefore cannot be determined from the material alone. Check the manufacturer’s approval and the specific thermal resistance.

PE film:
A PE film is primarily a separation or moisture-protection layer, not impact sound insulation. Whether it is required beneath your vinyl flooring depends on the subfloor, the floor build-up and the manufacturer’s requirements.

Common impact sound underlays for vinyl, suitable for improving acoustic performance and use with underfloor heating; *thermal resistance in m²K/W (the lower, the better)

Can you reuse an old impact sound underlay beneath vinyl flooring?

Reusing an old impact sound underlay can seem like a good idea because it saves valuable resources such as money, material and work. So why not leave the old underlay in place when switching to vinyl flooring? If you want to lay vinyl flooring over an existing underlay, you should make sure it is suitable.

For example, many people renovating a room switch from laminate to vinyl. Laminate may have very different types of underlay beneath it, such as wood-fibre boards, XPS foam or PE foam underlay. To find out whether you can reuse your old underlay, follow these points:

• Find out what type of underlay is beneath the old floor covering.
• Then check whether the installation instructions for the new vinyl flooring approve the existing underlay.
• Do not install another underlay on top of the existing one unless the manufacturer expressly approves this type of build-up.
• Not sure whether you can use the old underlay with your new flooring? If in doubt, ask a specialist. You are also welcome to email us at info@planeo.com or call us on 05222 960480
• Do not use an old underlay that is not approved for your new flooring. With polymer- or mineral-based click systems in particular, an underlay with sufficient compressive strength is important. As a technical guide, at least 200 kPa is used for such systems without an HDF carrier, and at least 400 kPa where higher requirements apply. The flooring manufacturer’s specification remains decisive.

Is an underlay actually necessary beneath vinyl flooring?

Many people wonder whether impact sound underlay is necessary for vinyl flooring. Not every vinyl flooring manufacturer always states clearly whether they consider an underlay necessary for their flooring.

Some people therefore want to install click vinyl without impact sound underlay, even though an underlay may be technically necessary.

So when is a vinyl flooring underlay necessary?

• Use an impact sound underlay for vinyl whenever the manufacturer requires it. The installation instructions specify which underlay may be used and how the floor build-up must be constructed. Following these requirements may be a condition of a voluntary manufacturer’s guarantee; statutory rights remain unaffected.
• If the vinyl flooring manufacturer does not give a clear statement about a separate impact sound underlay, do not automatically use just any underlay or PE film. Check the installation instructions and, if in doubt, ask the manufacturer or an experienced specialist retailer. A PE film serves different purposes from impact sound underlay.
• Whether an underlay is necessary also depends on the type of vinyl flooring. With vinyl flooring that has integrated impact sound underlay, a second underlay is generally not intended unless the manufacturer expressly approves it. A planeo solid click vinyl without integrated underlay, on the other hand, can for example be combined with the intended planeo Silence.
• Some people also want to avoid laying underlay because an old carpet is still in place and is intended to act as a substitute for impact sound insulation. However, this is not a good idea.

If you are still unsure whether a vinyl flooring underlay is necessary, this is often due to the different conditions on site. Further questions then arise, such as:

What subfloor are you laying the vinyl impact sound underlay on?

Does it make a difference whether the vinyl underlay is laid on screed, a timber subfloor or an old floor covering? In the VOB/C context, DIN 18365 remains the current ATV for floor covering work. Irrespective of this, for the specific vinyl flooring the subfloor must meet the manufacturer’s requirements and, in particular, be level, firm, dry and load-bearing.
Beyond these requirements, the following applies:

• On screed:
  Whether the subfloor is cement screed, anhydrite screed or mastic asphalt screed, the need for additional impact sound underlay and/or moisture protection depends on the vinyl flooring, the screed and the manufacturer’s specifications. A suitable PE vapour barrier may be required on mineral subfloors, but it does not replace impact sound underlay.
• On a timber subfloor:
  This may be old floorboards or rough-sawn boards, as well as OSB or chipboard. An approved underlay can be useful for improving acoustic performance if you want to install vinyl flooring without integrated underlay. At the same time, the entire build-up must be suitable for the timber subfloor; moisture protection should not be treated in the same general way here as on a mineral screed.
• On dry screed:
  Here, gypsum-fibre boards such as Fermacell dry screed or lightweight concrete provide the load-bearing function of the floor. Only use underlays that are approved for both the dry screed and the selected vinyl flooring.
• On old floor coverings:
  Old tiles are the most common existing floor covering used as a subfloor for vinyl. Read more about laying vinyl over tiles. Existing coverings such as PVC, linoleum or parquet may also serve as a subfloor for click vinyl, depending on their condition and the manufacturer’s approval. The key point is that the old covering is firmly fixed and the entire build-up meets the requirements of the new flooring.

Is impact sound insulation for vinyl necessary if there are no rooms below?

Since impact sound mainly affects rooms below the room in question and adjoining rooms, this is a reasonable question. The purpose of reducing impact sound is precisely to minimise noise in adjacent rooms. If there are no such rooms, you can at least dispense with it from this point of view.

However, reducing impact sound is not the only function of a vinyl flooring underlay. This leads to the question:

What other functions does a vinyl underlay perform besides reducing impact sound?

A good impact sound underlay for vinyl can also provide the following benefits:

• Just as important as improving impact sound is reducing walking noise to improve room acoustics. This noise is generated directly in the room itself. The quieter a floor sounds when walked on, the more pleasant the room acoustics can feel.
• The decoupling, meaning the separation of the vinyl flooring from the subfloor by means of a suitable underlay, can prevent direct contact between materials and therefore possible interactions such as plasticiser migration. At the same time, the floor can move within the product-specific limits.
• A subfloor may be sufficiently level within the required tolerances. Even so, very small irregularities may become visible through resilient vinyl flooring. This is known as the “telegraphing effect”. A suitable underlay can conceal small localised irregularities within its technical levelling capability. However, it cannot compensate for an uneven or unsuitable subfloor.
• An underlay with sufficient compressive strength supports the click joint and can therefore help prevent joint breakage and gaps. The decisive factor is the CS value of the specific underlay and the flooring manufacturer’s approval; there is no general value such as 40 t/m² that applies to all vinyl flooring.
• A suitable underlay can change how the floor feels underfoot and improve walking comfort. However, no general health benefit for joints or the back can be inferred from this.

What should you consider if the vinyl flooring has integrated impact sound underlay?

Because the impact sound function is already part of the flooring, a second underlay is generally not required. An additional soft underlay can even adversely affect the floor build-up and only makes sense if the manufacturer expressly approves it. This no longer applies only to HDF constructions: many rigid/SPC click floors already have an integrated acoustic underlay. On mineral subfloors, additional moisture protection may be required. The installation instructions for the relevant flooring specify whether a PE vapour barrier is needed and which one.

Does the type of vinyl flooring determine whether impact sound underlay is necessary?

Vinyl flooring is available in different constructions, so the requirements for impact sound underlay vary accordingly.

Click vinyl may, for example, be made as solid vinyl. Other variants include vinyl with an HDF carrier, an ISOCORE® carrier or other hardboard constructions. Today, rigid/SPC floors with a dimensionally stable mineral core are also widespread; many already have integrated impact sound underlay. There are also variants with cork.

Again, follow the information provided by the relevant manufacturer. If impact sound underlay is already integrated, an additional underlay is generally unnecessary unless the manufacturer approves a different build-up.

Not sure? Feel free to use our individual advice service: info@planeo.com

Impact sound underlay for vinyl over underfloor heating – does it work?

Some people attribute thermal-insulating properties to vinyl flooring. This is only true in the sense that vinyl flooring can feel warmer than some hard floor coverings, such as laminate.

An additional impact sound underlay for vinyl may therefore seem questionable because it creates resistance to heat transfer. This is known as thermal resistance.

Does a vinyl underlay allow heat from underfloor heating to pass freely to the floor covering?

How well an impact sound underlay for vinyl transfers heat is shown primarily by its thermal resistance R, measured in m²K/W. The lower the value, the less the underlay restricts heat flow. You can find the specific value in the product data sheet; depending on the product, relevant values may for example be stated in accordance with DIN EN 16354 or using thermal test methods such as EN 12664.

For a heated floor, what always matters is the total thermal resistance of the floor covering and underlay. A maximum of 0.15 m²K/W is commonly used as a technical guideline for such floor build-ups. This is not a blanket legal approval for every construction: also follow the requirements of the flooring and heating system manufacturers.

Here is how to calculate the thermal resistance of your vinyl flooring over underfloor heating:

Floor covering value + underlay value = floor build-up value (guideline for underfloor heating: max. 0.15 m²K/W)

High-density PU foam underlays such as planeo Silence or planeo SilentStick are currently specified with a thermal resistance of 0.01 m²K/W. This is favourable for a heated floor, provided the vinyl flooring itself and the rest of the build-up are also suitable. Another option with a low build-up height is to bond glue-down vinyl in a wet adhesive bed.

By contrast, cork or polystyrene underlays cannot be classified as generally unsuitable for underfloor heating. The specific R-value is what matters. Depending on the product, current XPS underlays for LVT/SPC/rigid flooring are, for example, around 0.03 to 0.04 m²K/W and may be approved for underfloor heating if the complete build-up remains within the manufacturer’s requirements.

Impact sound underlay for vinyl: the key points

Is impact sound underlay necessary for vinyl?

Choosing the right vinyl flooring underlay is important and should not be neglected. The installation instructions tell you whether impact sound underlay is required beneath the vinyl and which underlay is approved. The type of vinyl flooring also determines whether an underlay is needed. Vinyl flooring with integrated impact sound underlay generally does not require a second underlay unless the manufacturer specifies a different build-up. Following the installation requirements may be a condition of a voluntary manufacturer’s guarantee; statutory rights remain separate from this.

Which impact sound underlay is suitable for vinyl?

There is no single answer. First check the manufacturer’s approval, the type of vinyl flooring, the subfloor, compressive strength and, with underfloor heating, thermal resistance. Depending on the installation system, specific examples include PU underlays such as planeo SilentStick as a self-adhesive underlay, wineo silentCOMFORT as a grip underlay and the decoupling underlay planeo Silence. Specially developed XPS underlays can also be suitable for LVT/SPC/rigid flooring. Only use cork roll or latex underlays if the manufacturer approves them for your floor. A PE film, by contrast, is not impact sound insulation but serves as a separation or moisture-protection layer depending on the floor build-up.

Which impact sound underlay should you use beneath click vinyl?

To answer this question, you need to consider what type of click vinyl is involved. Click vinyl flooring is available as solid vinyl, with an HDF or ISOCORE® carrier, as rigid/SPC flooring or with other carrier constructions. It is therefore essential to follow the manufacturer’s information on the appropriate impact sound underlay. A planeo solid click vinyl without integrated underlay can, for example, be combined with the compression-resistant impact sound underlay planeo Silence. For click vinyl flooring with integrated impact sound underlay, an additional underlay is generally unnecessary.

Impact sound underlay for vinyl on screed: what should you consider?

Whether the subfloor is cement screed, anhydrite screed or mastic asphalt screed, the most important point is that it is level, firm, dry and load-bearing. Follow the manufacturer’s recommendation for the appropriate vinyl underlay. On mineral subfloors, additional moisture protection, such as a suitable PE vapour barrier, may be required. However, it does not replace impact sound underlay.

What are the benefits of impact sound underlay for vinyl?

• A suitable underlay can improve walking comfort.
• Impact sound reduction and walking sound reduction can help create more pleasant room acoustics.
• A suitable impact sound underlay can decouple, separating the vinyl flooring from the subfloor and avoiding direct contact between materials.
• It can conceal small localised irregularities within its technical levelling capability, but it does not replace a properly prepared subfloor.
• An underlay with sufficient compressive strength supports the click joint and can therefore help prevent joint breakage and gaps. The manufacturer’s approval and CS value are decisive.