Do Thick Carpets Need Underlay? How to Choose the Right Combination

This is a common question and the short answer is Underlay is always recommended but not mandatory. An underlay can make your carpet last longer and acts as a protective layer between the hard floor and the carpet, not to mention the extra cushioning it can provide. When choosing a thick carpet, it is important to consider the underlay you will use with it. The right underlay depends on the carpet's construction, density, intended room and support requirements. Choosing the thickest available underlay does not necessarily mean you will get the best results.

A thick carpet can work well with an 8mm, 9mm or 10mm underlay, depending on the product. The aim is to find the right balance between comfort, support and total floor height and price. A suitable underlay should cushion the carpet while providing enough support and avoiding problems with doors and furniture.

Why Does Underlay Thickness Matter When Choosing Thick Carpet?

The underlay sits between the carpet and the subfloor. It provides cushioning, helps absorb everyday foot traffic and can improve thermal and sound insulation.

Here are the main things to consider:

• Comfort: Underlay adds cushioning beneath the carpet.
  
• Support: It helps the carpet cope with everyday foot traffic.
• Insulation: Some underlays help reduce heat loss and sound transmission.
• Carpet protection: A suitable underlay can help absorb impact and reduce wear and also acts as a protective layer between the hard floor and carpet backing.
• Floor height: A thicker underlay increases the overall height of the flooring, this can impact door clearances.

Should You Use 8mm, 9mm, 10mm or 11mm Underlay with Thick Carpet?

Underlay thickness	What to expect	Suitable consideration
8mm	Moderate cushioning  with a lower overall floor height	Bedrooms and everyday domestic rooms
9mm	A balance between comfort and support	Living rooms and general household use
10mm	More cushioning underfoot	Rooms where extra comfort is preferred
11mm	A thicker option that can provide additional cushioning	Where the carpet and installation requirements allow it

Remember that thickness is only one part of underlay performance. Density, material, compression recovery and suitability for the carpet are equally important.

For example, a high-density 9mm underlay may provide better support than a softer underlay that is thicker. Always compare the complete specifications rather than choosing by millimetres alone.

Can Thick Carpet and Thick Underlay Make the Floor Too High?

Yes. Combining a thick carpet with thick underlay increases the total floor height, which can create practical problems during installation.

For example:

Carpet thickness	Underlay thickness	Combined nominal thickness
12mm	8mm	20mm
14mm	9mm	23mm
15mm	10mm	25mm
15mm	11mm	26mm

These figures are simple estimates before compression and installation differences. Check whether the carpet measurement refers to pile height or total construction thickness.

Before choosing your combination, check:

• Whether doors will open and close without catching.
  
• Whether the new carpet will sit level with adjoining flooring.
  
• Whether door bars and thresholds can accommodate the extra height.
  
• Whether stairs and landings can be fitted safely.
  
• Whether the underlay is suitable for the carpet and subfloor.
  
• If you are unsure, ask your carpet fitter to check the measurements before ordering.

Is Thicker Underlay Always Better for Thick Carpet?

Not necessarily. A thicker underlay can provide more cushioning, but too much softness may affect how the carpet performs.

If the underlay compresses excessively under regular foot traffic, the carpet may move more than intended. This can put additional strain on the carpet backing and fitting.

For busy areas such as hallways and stairs, support and durability are particularly important.

For bedrooms and less frequently used rooms, you may have more flexibility to prioritise comfort, provided the carpet manufacturer and fitter approve the combination.

Our Recommended Thick Carpets

Here are five thick carpet options to consider when planning a comfortable flooring installation.

1. Kenvy Beige Thick Carpet

Best for: Bedrooms and living rooms where a soft neutral finish is preferred.

Kenvy Beige has a 15mm pile, dual backing and 100% polyester construction. It is listed as suitable for domestic use and underfloor heating, making it an option for homeowners looking for a thick, easy-to-clean carpet.

Perfect Match: Kenvy Beige Carpet

Price: Now only £24.75 m2

2. Canaries Oatmeal Thick Carpet

Best for: Busy households looking for a warm neutral shade.

Canaries Oatmeal has a 14mm pile, polypropylene fibres and dual backing. It is stain-resistant and rated for heavy domestic use, making it worth considering for living rooms and other frequently used areas.

Perfect Match:   Canaries Oatmeal Carpet

Price: Now only £15.97 m2

3. Kenvy Silver White Thick Carpet

Best for: Creating a light and bright appearance.

This 15mm polyester carpet features dual backing and a soft finish. Its silver-white shade can work well in bedrooms and living spaces where you want a lighter flooring colour.

Perfect Match:  Kenvy Silver White Carpet

Price: Now only £24.75 m2

4. Granada Elite Thick Blue Carpet

Best for: Adding colour while keeping a thick, comfortable carpet finish.

Granada Elite has a 15mm pile, dual backing and an easy-to-clean construction. Its blue colour offers an alternative to traditional beige and grey carpet shades.

Perfect Match: Granada Elite Thick Blue Carpet

Price: Now only £19.75 m2

5. Grand Deluxe Oatmeal Twist Pile Carpet

Best for: Homeowners who want a thick carpet suitable for everyday use.

Grand Deluxe Oatmeal has a 12mm pile, a twist-pile construction and dual backing. It is made from polyester and rated for heavy domestic use, making it an option for bedrooms, living rooms and hallways.

Perfect Match: Grand Deluxe Oatmeal Carpet

Price: Now only £29.99 m2

Our Recommended Underlays for Thick Carpet

The following underlays offer different thicknesses and performance features. Choose according to your carpet, room and installation requirements.

1. 10mm Luxor Yellow Thick Underlay

Best for: Homeowners looking for additional cushioning.

This 10mm PU foam underlay has a stated 2.47 TOG thermal insulation rating and 38dB sound insulation rating. It is suitable for wooden and concrete floors and is listed as compatible with underfloor heating.

Perfect Match: 10mm Luxor Yellow Underlay

Price: Now only £49.99

2. QA Gold High Density Underlay

Best for: Those prioritising density and support.

The QA Gold PowerWalk underlay is described as a high-density PU foam option with a density of 130kg/m³. Its product description highlights compression recovery, sound reduction and thermal insulation.

Important: The product title refers to 11mm, while the listed key features state 9mm. Confirm the actual thickness with the retailer before ordering.

Perfect Match: QA Gold High Density Underlay

Price: Now only £69.99

3. 11mm Cloud9 Underlay

Best for: Homeowners looking for a thicker underlay option.

Cloud9 is a recognised underlay brand, and this product is listed at 11mm thick. It is also stated to be suitable for underfloor heating. Check its full technical specifications and compatibility with your chosen carpet before fitting.

Perfect Match: 11mm Cloud9 Underlay

Price: Now only £149

4. QA Silver 9mm Underlay

Best for: A balance between cushioning and support.

QA Silver is a 9mm high-density PU foam underlay with a stated density of 130kg/m³. Its product information highlights compression recovery, a 2.3 TOG rating and 38dB sound reduction.

Perfect Match: QA Silver 9mm Underlay

Price: Now only £24.75 m2

How to Choose the Right Carpet and Underlay Combination

Before ordering, think about where the carpet will be installed and how the room is used.

• For bedrooms: Comfort may be a priority, so consider a suitable cushioned underlay that does not make the floor excessively high.
• For living rooms: Look for a balance of cushioning and support because the carpet is likely to receive regular use.
• For hallways and stairs: Prioritise a supportive, durable underlay rather than choosing the thickest option.
• For underfloor heating: Check the combined tog rating of the carpet and underlay against the heating manufacturer's requirements.
• For doorways: Measure the available clearance before choosing a thick carpet and underlay combination.

You can compare different options in the carpet underlay collection before deciding which thickness is right for your installation.

If you are specifically looking for a deeper, softer carpet finish, browse the thick and soft carpet collection to compare available styles.

Final Thoughts

Thick carpet does not always need a thick underlay. The best combination is one that provides comfort, support and durability without creating unnecessary floor height.

Before buying, compare the carpet's construction with the underlay's thickness, density and performance. Also check door clearance, adjoining flooring and underfloor heating requirements.

Choosing the right combination can help your carpet feel comfortable underfoot while providing the support it needs for everyday use.

You can also visit the Carpets Online to browse more flooring options for your home.

Frequently Asked Questions