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Carpet Underlay Explained

Choosing a carpet for your home is just a small piece of the overall jigsaw. Forget about which carpet brands you decide to go with, or which carpet patterns work best, because if you fail to install a decent underlay then it will have all been in vain.


Along with purchasing a new carpet, the underlay is the other most important factor to take into consideration. Its addition could help prolong the lifespan of your carpet, while providing it with some much-needed support and comfort to help you get the most out of your new investment.


Underlay also provides various benefits such as thermal insulation, sound proofing, and can even insulate against dust and drafts. Furthermore, underlay can also increase the aesthetic appeal of a room through raising the level of the floor and preventing it from buckling under pressure.


If you are looking at purchasing a new wall to wall carpet for your home and you’re unsure about your underlay options, then take a look at some of our frequently asked questions to give you a better idea of where to start.


Frequently asked carpet underlay questions


1. Why use carpet underlay?

We have listed below the reasons why carpet underlay is a vital component:


Heat insulation

Carpet underlay essentially adds an extra layer of insulation, which helps reduce the amount of heat lost through the floorboards.


Sound insulation

The extra layer of insulation helps reduce any noise from escaping or penetrating the room, while it prevents noise from affecting the room below.



Most carpets are fitted using a method which stretches the carpet onto grippers around the edge of a room. Carpet underlay helps raise the level of the floor so that it is inline with the grippers, making it easier to install.



Underlay absorbs any wear and tear your carpet may experience, thus keeping it looking preserved for longer. In addition to this, it also minimises furniture installations due to the extra give that is provided.


2. Can I lay carpet on my existing underlay?

We firmly believe that laying carpet on a pre-existing underlay is false economy. An old underlay will have become flattened and less resilient and this will naturally affect the overall effectiveness of a new carpet.


3. Do I need underlay for my stair carpet?

Yes - using carpet underlay for your stair carpet works the same as it would with any other part of the house. Before doing anything you need to remove any of the old underlay, tracks, nails and staples and clean down the area.


An important thing to note about using stair carpet underlay is that it reduces noise from a large suspect noise area, while it also keeps the carpet stable and safe.


4. Do all carpets require underlay?


Woven carpets

If you are thinking about installing woven carpets in your room, then it is vital that you use carpet underlay. They do not have cushioned backing so therefore it is a necessary addition.


Secondary backed carpets

As perhaps one of the most common types of carpet used in the domestic market, you’d think they would have adequate backing. This is not the case however, so underlay is required.


Felt backed carpets

These carpets have a thin back and despite being sold as having underlay in some instances, they aren’t very effective. We’d recommend purchasing underlay in addition to this type of carpet.


Foam backed carpets

Because of the nature of their design and materials used, underlay is not required for this type of carpet.


5. What are the best underlays for concrete floors?

We would recommend using an underlay with a higher tog rating as it will provide excellent thermal insulation and will prevent any heat being transferred away. It can also reduce any cold air from the concrete floor from affecting the carpet.


6. What is a tog rating?

The thermal resistance of any type of carpet or underlay is measured by its tog rating. This means that the higher the tog rating, the better it is at insulating the room. So the lower the the tog rating the better it is at underfloor heating.


7. How do I check how much underlay I need?

This process is actually quite simple. All you need to do is measure your rooms’ widest and longest point in metres and multiply it by two (depending on how much you want to use). For instance, Length A x Width A = Area A


NOTE: You should make allowance for wastage that occurs during fitting, as well as any objects in the room such as fitted baths, fixtures or cabinets.


8. What is carpet underlay made of?

There are three main types of material which help make carpet underlay:



The most common form of carpet underlay is made using a form of synthetic rubber, which is made using old car tyres. Rubber has a greater resilience against carpet wear, while it also has effective sound proofing qualities.


Rubber underlay comes in two forms: sponge textured or crumb. The former is considered to be more comfortable, whereas the latter is much longer-lasting and durable.


PU Foam

This form of underlay is made from using recycled furniture foam. This is one of the lighter forms of underlay available and offers a soft base, as well as providing better thermal insulation.



Felt underlay is crafted using a high percentage of wood fibre. Although this form of underlay is used considerably less than its alternatives, it does have extremely good thermal insulation qualities thanks to its high wool content.


If you’re looking at purchasing a new bespoke carpet for your home and want the very best carpet underlay advice, then why not get in touch with us today and see how we can help? Visit and let us get you the help you need.

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