The ultimate guide to underlay

Your underlay is an important purchase not to be forgotten once you’ve chosen your dream floor. You may have a few questions about why you need it, why it’s important, as well as the different styles and thicknesses available. Read on to learn more about choosing the right underlay for you as we guide you through with our expert advice.

What is underlay?

Underlay describes the thin layer of material fitted over your subfloor and underneath your desired flooring to create a cushioning layer between the two. It can be made from a variety of materials including rubber, felt, fibre or foam and each have their own beneficial properties.

Why do you need underlay?

Before we dive in let one of our flooring experts take you through some of the main reasons why underlay is so important in the video below.

Underlay brings with it a whole host of beneficial properties, the first being that it is fundamental to flooring.

Offering both comfort and protection, underlay helps create a smooth and even surface layer for a high-quality finish.

Sometimes the subfloor in which your flooring is going to be fitted over can be uneven, luckily the underlay helps to rectify this.

Underlay is also used if your flooring has a textile or latex backing.

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Benefits of underlay

Making sure you choose the right one for you and your flooring is essential as it lays the foundations for the longevity of your flooring. In fact, underlay makes your carpet last up to 40% longer. 

At ScS we strongly recommend that new underlay is laid when your new carpet, wood or laminate flooring is fitted.

New underlay has many benefits and will also help to make sure that you get the most out of your new flooring.

Underlay will:

  • Give you extra cushioning, making your carpet, wood or laminate flooring even more comfortable underfoot
  • Help to insulate your room, retaining heat which can help to reduce your energy bills
  • Help to reduce noise - ideal for family homes or those living in flats
  • Help to prolong the life of a carpet by up to 50%
  • Act as a shock absorber for carpets, allowing them to withstand more wear and tear
  • Reduce air borne sound under laminate and wood flooring.

Poor quality underlay can lead to the risk of voiding your carpet warranty, but our carpet specialists are happy to help you determine which type of underlay will provide the best support for your carpet.

Does underlay need replacing?

You may be wondering if you need new underlay; seeing as it’s out of sight and it’s protected by your actual flooring, so is less likely to wear down that quickly. However, overtime underlay begins to wear and dirt and bacteria can build up, so you should ideally replace your underlay every time you have new flooring

When don’t you need an underlay?

If your flooring already has a built-in underlay, such as felt-backed carpets, you don’t need underlay.

This multi-purpose solution eliminates the need to purchase underlay separately, so this is a great option if you’re on a budget.

Which thickness do I need?

We offer a variety of underlay thicknesses ranging from 8-12mm which allows you to tailor the comfort level.

The thickness of underlay is a critical factor as it helps to retain heat and prevents sound from echoing around your house. A thicker underlay is particularly desirable in upstairs rooms such as your bedroom or landing. 

While the TOG rating, just like the TOG rating that’s used for duvets, indicates how effective the underlay is at preventing heat from escaping. The higher the TOG rating, the better the heat retention.

Top tip: If you’re getting thicker underlay, the gap between your flooring and the bottom of your doors will be smaller. In some instances, you may need to get your doors skimmed to make sure you can still open and close them.

Why is it important what your underlay is made from?

What your underlay’s made from is crucial in ensuring it provides maximum comfort, helps your flooring last longer and provides an extra layer of insulation and noise reduction.

When it comes to choosing which underlay is right for you, it helps to know your options. Let’s look into the varying materials underlay can be made from: 

  • Polyurethane foam (PU) – made from recycled furniture foam and a good heat and sound insulator
  • Crumb rubber – a hard-wearing and durable option 
  • Waffle – provides a good sound barrier and enhanced comfort
  • XPS foam boards – made from foamed long-lasting polystyrene 
  • Luxury vinyl - fitted underneath luxury vinyl tiles and provides good sound and thermal absorption

Top tip: Crumb rubber underlay is incredibly springy, which means it’s more likely to spring back after having heavy items (e.g. furniture) placed on it.

While it may quite literally be a fundamental layer within the process of choosing and purchasing new carpet underlay or laminate underlay; it’s easy to overlook.

Whilst we see underlay initially when it’s being fitted, it’s then out of sight and out of mind for however many years your new flooring’s down for.

As a result, it can be easy to forget about factoring in underlay until the next time comes for you to invest in some new flooring, which means what you decide on may not necessarily be the best option.

Can underlay be eco-friendly?

It certainly can!

There are eco-friendly underlay options available that are helping tackle the global plastics pollution crisis.

Including British made SpringBond®, an eco-engineered carpet underlay created using fibres made from recycled PET plastic bottles and other single-use plastics. 

Available in both a 9mm and 11mm thickness, SpringBond is a quieter, safer, greener alternative to PU foam underlay.

Made up of 85% recyclable materials and is 100% recyclable, SpringBond provides maximum performance with minimal environmental impact. 

Here are the main benefits of using SpringBond underlay:

  • A greener option
  • Manufactured here in the UK, that travels fewer miles to reach your home
  • It is a polyester underlay using only 15% new polyester to bond with the remaining 85% together
  • The manufacturing process is chemical-free
  • Produced in a waste-saving, efficient 1.5m wide roll that is lightweight, and easy to lift and cut
  • Proven to reduce impact noise, so it’s perfect for multi-floor use in a busy household, whether placed upstairs or downstairs
  • Improves sound absorption up to 57 DB
  • It uses virtual spring technology which creates natural bounce back increasing the underlays dimensional stability
  • Offers thermal installation up to 2.3 TOG
  • Dust-free 

In fact, we’re incredibly proud to say that thanks to so many of you choosing this eco-friendly underlay you’ve helped to save a remarkable 1 million plastic bottles from the sea. 

We also offer carpet ranges made from discarded marine waste – Sedna® carpets take waste, such as old fishing nets, and transform it into soft, luxurious, and durable carpet.

What’s more, Sedna® carpets are also fitted with an ECO FusionBac textile back made from 100% recycled PET plastic bottles.

Considerations when purchasing underlay

Before you purchase your new underlay, there are a few important factors to consider beforehand.

Ensure you ask yourself the following: 

What room will it be fitted in?

Ideally, you should have underlay underneath all of your upstairs and downstairs flooring because it will, among many things, help prolong the life of your flooring.

But that doesn’t mean you should have exactly the same underlay throughout your entire house.

For instance, a firmer underlay is better for areas where there’s more wear and tear and heavy items placed on it, such as your living room or stairs. Because it’s firmer, it helps prevent your flooring from moving and, in the case of carpets, creasing and stretching.

Meanwhile, softer underlay is better suited to low traffic areas; such as your rarely used spare room or downstairs toilet, where it’s less likely to be a be a busy area of your home.

Top tip: 9mm underlay is the best thickness for stairs; it’ll provide the right amount of cushioning without being too bulky to fit.

What flooring will it be fitted under?

What you intend to put on top of your underlay will influence the type of underlay you have.

For example, rigid underlays made from plywood and MDF are used for wooden flooring because they provide a level foundation, distribute weight load evenly and help reduce movement.

In comparison, softer underlays made from materials, including foam, rubber and recycled plastics, are used underneath carpet.

Depending on the thickness and type of insulation you go for, they provide varying degrees of padding and sound and heat insulation.

Certain types of underlay also exist for hard flooring too, some of which incorporate special damp-proof membranes.

Top tip: Match your underlay to your flooring type. Different underlay is suitable for different areas of your home, especially if you have a mixture of carpet, laminate and tiled flooring. You need a specific underlay if you have underfloor heating.

Best underlay options

Discover a few of our underlay options and find the one that's right for you.

  • 9mm or 11mm thickness
  • 100kg/m³ density
  • Tog rating 2.1
  • Made from 85% recycled plastic bottles
  • Offers thermal insulation
  • Suitable for all rooms & recommended for areas of heavy use
  • 7mm thickness
  • 80kg/m³ density
  • Tog rating 2.0
  • Budget friendly option
  • Suitable for all rooms & recommended for areas of light use
  • 11mm thickness
  • 100kg/m³ density
  • Tog rating 4.1
  • Thermal & sound insulation
  • Suitable for all rooms & areas of heavy use 
  • 11mm thickness
  • 80kg/m³ density 
  • Tog rating 2.0
  • Suitable for all rooms & recommended areas of heavy use
  • 5mm thickness
  • 400 kg/m³ 25lbs/cu.ft density
  • Recommended for wheelchair use or in an office environment 
  • Suitable for double-stick and stretch-fit installation of carpets and natural floor coverings
  • Suitable for use with underfloor heating
  • Recommended for areas of heavy domestic & commercial use
  • 8.3mm thickness
  • 46.6 kg/m³ density
  • Suitable for use with underfloor heating
  • Suitable for all rooms and recommended for areas of medium use
Underlay options for laminate flooring

These underlay products are suitable for use under laminate flooring and will add a great deal of comfort, stability and warmth to your flooring.


  • 2mm thickness
  • 20 kg/m³ density
  • Tog rating 2.1
  • Very effective acoustic properties
  • An economic solution for insulating laminate floors
  • 3mm thickness
  • 30 kg/m³ density 
  • Tog rating 0.87
  • Features a integral silver foil vapour control layer
  • Ideal for use with underfloor heating systems

Published: 14th July 2022