Do I Need Underlay For My Carpet?

By Author: carpetsonline
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In most cases, yes, you should use an underlay with any carpet. A good-quality underlay can make the carpet feel softer and more comfortable underfoot, help reduce wear, improve insulation and provide additional sound reduction. It can also help the carpet sit properly and perform as intended. However, the best underlay depends on the carpet, room, traffic level and existing flooring. Some manufacturers will also give an extended guarantee if new underlay is laid before carpet installation.
Do You Really Need Underlay Under Carpet?
Underlay is not always legally or technically required, but it is strongly recommended for carpet installations.
Think of underlay as the layer between your carpet and the floor underneath. It provides cushioning while helping protect the carpet from the impact of everyday foot traffic rubbing the carpet backing against the hard wood or concrete floors.
Installing a carpet without a suitable underlay can mean the carpet feels harder underfoot and may wear more quickly, particularly in busy areas such as hallways, stairs and living rooms.
For a new carpet, replacing the ...
... old underlay at the same time is usually a sensible investment.
There are cases where te budget conscious have enough for the carpet but not for the underlay, sometimes a felt back carpet is chosen with the perception that he felt acts as a better backing layer than an acton back when there is no underlay.
What Does Carpet Underlay Do?
Underlay has several important jobs. It is not simply there to make your carpet feel softer.
Makes Carpet More Comfortable
One of the biggest benefits of underlay is the extra cushioning it provides.
A suitable underlay gives your carpet a softer, more comfortable feel underfoot. This can make a noticeable difference in bedrooms, lounges and other rooms where you spend a lot of time.
Helps Your Carpet Last Longer
Carpet fibres are affected by repeated foot traffic. Every time someone walks across the carpet, pressure is placed on the pile.
Underlay absorbs some of this impact and helps reduce the amount of stress placed between th carpet backing and the floor underneath.
Improves Insulation
Carpet already provides some insulation, but adding underlay can improve the overall thermal performance of the floor.
A good underlay can help reduce heat loss through the floor, making rooms feel warmer and more comfortable.
Reduces Noise
Underlay can help absorb some of the sound produced by footsteps and movement.
This makes it particularly useful in upstairs bedrooms, children's rooms and homes where reducing noise between floors is important.
Helps the Carpet Look Better
A suitable underlay helps create a more even, stable surface for the carpet.
This can help the carpet sit properly and maintain its appearance rather than looking flat or uneven after regular use.
Adds Protection Between the Carpet and Floor
Underlay creates a protective layer between your carpet and the subfloor.
It can help reduce the effects of minor imperfections in the floor while also preventing the carpet backing from rubbing directly against the floor.
When might you not need a separate underlay?

You may not need traditional separate underlay when:
The carpet has an integrated or specialist backing designed for direct installation
The manufacturer specifically recommends installation without underlay
The room has underfloor heating and the underlay may stop the heating coming through efficiently 
The existing installation has a suitable compatible layer that does not need replacing

Always check the carpet manufacturer's installation recommendations before making a decision.
Should I Replace Old Underlay When Buying New Carpet?
In most cases, yes.
It can be tempting to save money by keeping your existing underlay, particularly when the old carpet is being replaced. However, the underlay also becomes compressed and loses some of its cushioning over time.
Old underlay may also have:

Flattened areas
Uneven sections
Loss of support
General wear
Damage from previous installation
Dirt or odours

Putting a new carpet over worn-out underlay can reduce some of the benefits you would otherwise get from the new carpet.
If the existing underlay is still in excellent condition and is compatible with the new carpet, it may be possible to reuse it. Your carpet fitter should check this before installation.
Does Thicker Underlay Mean Better Underlay?
Not necessarily.
A thicker underlay can provide more cushioning, but thickness is only one factor to consider. The density, construction and intended use of the underlay are also important. As an example the QA Gold underlay here is a very dense heavy duty underlay, whereas the 8mm Underlay is a thick but lighter density underlay for those on the budget.
For example, a very soft underlay may feel comfortable in a bedroom but may not be the best choice for every high-traffic area.
The ideal underlay should provide the right balance of:

Comfort
Support
Durability
Insulation
Noise reduction
Compatibility with your carpet

It is also important to follow the carpet manufacturer's recommendations because some carpets perform better with specific types of underlay.
What Type of Underlay Is Best for Carpet?
There isn't one underlay that is perfect for every carpet or room.
Foam Underlay
Foam-based underlays are lightweight and can provide good cushioning and insulation.

They can be a practical option for homeowners looking for a comfortable floor covering without excessive weight.
Rubber Underlay

Rubber underlay is known for its durability and supportive feel. It can also provide good sound insulation, making it useful in areas where reducing noise is important.

PU Foam Underlay

PU foam underlay is popular because it can provide a comfortable feel while offering good insulation and support.

It is available in different densities and thicknesses, so the right specification depends on the carpet and room.

Felt Underlay

Felt underlay has traditionally been used with carpets and can provide a firm, supportive base.

The best option depends on the carpet type, installation requirements and the conditions in the room.
How Do I Choose the Right Underlay for My Carpet?
Before buying underlay, consider the carpet type, room, traffic level and floor underneath.

For Bedrooms

Bedrooms generally have less foot traffic, so comfort and warmth may be priorities.

A comfortable underlay can make a bedroom carpet feel noticeably softer.

For Living Rooms

Living rooms typically receive moderate to heavy daily use.

Choose an underlay that provides good cushioning while still offering enough support for regular foot traffic.

For Hallways

Hallways experience some of the highest levels of foot traffic in a home.
A durable, supportive underlay is usually more important here than choosing the softest option available.
For Stairs
Stairs need particularly careful consideration because the carpet is subjected to repeated foot traffic and movement.
Always follow the carpet manufacturer's recommendations and use an underlay suitable for stair installation.

Carpet Underlay vs No Underlay

Feature

With Underlay

Why It Matters

Comfort

Softer and more cushioned

Generally firmer

Carpet support

Better support

Less cushioning

Insulation

Improved

Lower

Sound reduction

Better

Less effective

Carpet protection

Helps reduce impact

Carpet takes more direct impact

Long-term performance

Generally better

Can be reduced depending on carpet

Initial cost

Higher

Lower

 
Although skipping underlay can reduce the initial installation cost, it may not provide the best long-term value.
Can Underlay Be Used With Underfloor Heating?
Some underlays are suitable for use with underfloor heating, but not every underlay is.
If your home has underfloor heating, check the carpet and underlay specifications before installation. The combined carpet and underlay construction needs to allow heat to pass through effectively.
Look for products specifically stated as suitable for underfloor heating and follow the manufacturer's recommendations.
Our Best Carpet Underlay Recommendations
If you are buying a new carpet, choosing the right underlay can make a noticeable difference to comfort, insulation and how the carpet performs over time. Here are three thick underlay options from Carpets Online worth considering:
8mm Luxor Silver Thick Underlay
The 8mm Luxor Silver Thick Underlay is a good option if you want to add extra cushioning beneath your carpet without choosing one of the thickest underlays available. Its 8mm construction provides a supportive and comfortable base for everyday carpet use.
Best for: Bedrooms, living rooms and general domestic use.
A practical choice for homeowners looking for a balance between comfort and support.

Perfect Match: 8mm Luxor Silver Thick Underlay
Price: Now only £39.99
10mm Luxor Yellow Thick Underlay
The 10mm Luxor Yellow Thick Underlay provides an additional level of cushioning compared with an 8mm option. Its thicker construction can help create a softer and more comfortable feel underfoot, making it suitable for homeowners who want extra comfort from their carpet installation.
Best for: Living rooms, bedrooms and areas where comfort is a priority.
Ideal for pairing with carpets where you want a noticeably cushioned feel underfoot.

Perfect Match: 10mm Luxor Yellow Thick Underlay

Price: Now only £49.99

High Density 11mm Underlay 

If you're specifically interested in density as well as thickness, the High Density 11mm Underlay is another option to consider. An 11mm high-density underlay can provide a combination of cushioning and support beneath the carpet.
This is particularly relevant when choosing a quality carpet because, as with carpet itself, thickness and density are not the same thing. A good underlay needs to provide enough support rather than simply being as thick as possible.
Best for: Homeowners looking for a thicker underlay with a focus on support and density.

Perfect Match:  QA Gold High Density 11mm Underlay (15m2 Roll)
Price: Now only £69.99

Final Thoughts
For most carpet installations, underlay is a worthwhile investment rather than an unnecessary extra. It can improve comfort, insulation, sound reduction and support while helping your carpet cope with everyday use.
When buying a new carpet, don't just compare the carpet itself. Consider the carpet, underlay and fitting together to get the best result for your home. At Carpets Online, choosing the right combination can help you create a more comfortable and longer-lasting floor.
Frequently Asked Questions
Question -: Do all carpets need underlay?

Answer-: Most carpets benefit from suitable underlay, but not every carpet requires separate underlay. Some specialist carpets have backing systems designed for particular installation methods, so always check the manufacturer's instructions.

Question -: Can I put new carpet over the old underlay?

Answer-: You can sometimes reuse existing underlay if it is in good condition and compatible with the new carpet. However, worn, flattened or damaged underlay should generally be replaced.

Question -: Does underlay make carpet softer?

Answer-: Yes, a suitable underlay can make carpet feel softer and more comfortable underfoot by adding cushioning beneath the carpet.

Question -: Does underlay make carpet last longer?

Answer-: Good-quality underlay can help support the carpet and reduce the impact of repeated foot traffic, which can contribute to better long-term carpet performance.

Question -: Can I use the same underlay throughout my house?

Answer-: You can, but it isn't always the best approach. Different rooms have different traffic levels and installation requirements, so the most suitable underlay may vary.

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