UNDERLAYS cannot be seen and are quite often overlooked when it comes to the design and specification process, but they are a very technical product offering great benefits to a project.
It is worth understanding the many benefits when the correct use of the appropriate underlay is used for all types of flooring installation.
Underlays were first made of felt and used under carpet squares in the 1940s, moving during the 1950s in America to be used for wall-to-wall carpets. This heralded the introduction of rubber underlays designed to help the carpet sit properly and wear evenly.
As the decades progressed more research and development happened leading to a very technical product that offers enormous benefits to a project.
A good-looking and wrinkle-free carpet that looks better for longer is important. And despite the introduction of PU underlays and their rise in popularity, there is still nothing quite like a rubber underlay to increase the comfort level of floorcoverings of all types.
Rubber underlays are widely used in the UK; the familiarity has meant that consumers have never shown any resistance to them. In fact, pound for pound rubber underlays generally deliver better value for money in construction, comfort, and durability.
It’s therefore worth spending some time getting to know the different options and to understand the many benefits arising from the correct use of the appropriate underlay for all types of flooring installation.
There are two types of rubber underlay: sponge rubber and crumb rubber.
Sponge rubber underlays are the most traditional form of underlay. They have been around since the 1950s for very good reasons. They are extremely comfortable and no other underlay produces quite the same feel underfoot. They are also exceptionally good at minimising both impact sound and airborne sound between rooms. They are incredibly flexible and cover more applications than any other type of underlay. They are heavier and denser than PU foam. Specialist applications include low tog underlays for underfloor heating and thin and dense underlays for hard flooring.
Crumb rubber underlays are, as the name suggests, made from small crumbs of rubber which are bonded together. The rubber crumbs come from used car tyres, so the basic raw material comes from 100% recycled sources. In addition, crumb rubber underlays are fantastically durable and amazing at reducing impact and airborne noise. They are also dimensionally stable with regard to lateral forces. In other words, they don’t stretch or tear easily. Crumb rubber underlays offer outstanding recovery and longevity. This makes them ideal for high traffic and very large areas.
Why choose rubber underlay?
The main reason people choose rubber underlay is for underfoot comfort. Certain sponge rubber underlays offer without doubt the most luxurious feel, while crumb rubber is extremely hard wearing and offers 94% recovery with nothing else offering the same durability for high traffic commercial areas.
The benefits of rubber underlay include:
- Makes carpets feel better: provides the cushioning that makes the carpet so comfortable and luxurious underfoot.
- Makes carpets look better: protects the carpet and helps to prevent the pile from flattening thereby helping the carpet look new for longer.
- Improves insulation: helps keep in the heat, which will reduce energy bills. Some studies have suggested that underlay can reduce energy costs by up to 15%. Thickness, density and composition dictate the tog rating of underlay which is a measure of heat insulation. The lower the tog rating the better an underlay is for use with underfloor heating because more heat can rise through the flooring and into the room. Conversely, a higher tog rating gives a greater level of heat insulation which is perfect for use with conventional heating systems.
- Helps reduce noise: acts as a barrier to sound. A carpeted floor is quiet but a carpet with an underlay can be 2.5 times quieter. Specialist underlays for wood and laminate floors can reduce in-room noise by up to 50%.
- Makes carpets last longer: acts as a ‘shock absorber’ so carpets suffer less wear.
- Improves hygiene: protects the carpet pile making it easier to clean and thus more hygienic.
Which underlay? Match the product to the customer’s needs
It’s always better to buy the right underlay to complement the preferred choice of floorcovering and to maximise its performance according to its location. The first question to ask is: what is the flooring’s primary requirement?
Comfort may be a priority in bedrooms and other living areas, while durability is a must in areas such as stairs, halls and landings which see a lot of traffic.
Keeping noise to a minimum might be important for people living in flats, or for those who have young children, or for people who prefer hard flooring, while people with underfloor heating will want an underlay with a very low tog rating.
When it comes to choosing underlay for the home environment, comfort is likely to be a major consideration. More than 70% of consumers say that comfort is important to them when it comes to selecting an underlay.
And that’s no surprise. After all, a good quality underlay can make even a budget carpet feel luxurious. This makes it an especially important feature in rooms where people like to relax, such as the lounge and bedroom.
There are several factors that contribute to making an underlay comfortable. These include the ‘sponginess’ of the underlay material, along with its thickness and density. The combination of thickness and density is all important as a thick underlay with low density may not perform well. Typically, the thicker the underlay, the better quality it will need to be – 11mm is often used for luxury installations with 9mm and 7mm the common domestic thickness, but rooms with heavy traffic will need a thinner, denser pad.
Airborne sound can be a constant problem; whether it’s children learning to play drums in their upstairs bedrooms or noisy neighbours, noise leaking from one room into another can completely disrupt the peace and quiet.
The solution is a simple one. Adding mass into a partitioning wall or floor can help to reduce the transmission of airborne sound between rooms.
High density sponge rubber and crumb rubber underlays with a combination of both density and thickness, which equates to a mass per square metre, are the ideal choice to keep noise to a minimum.
Impact noise can be a real problem for areas where hard flooring has been installed, and with the current trend towards this type of floor in both domestic and commercial settings, there are now specialist rubber underlays available for use with wood, laminate, and luxury vinyl tiles (LVT).
Tests have shown that in-room acoustics can worsen if inferior or lightweight underlays are used with hard flooring; putting a lightweight, air filled, cellular product under wood or laminate creates an echo chamber and more noise, whether it’s generated by scraping furniture, heavy footsteps, or reverberation.
Special noise reduction rubber underlays for hard flooring, with their superior weight and density, reduce acoustic noise levels by up to 30 per cent.
That’s why an acoustic resilient membrane significantly reduces impact sound and is widely used as a soft floor covering or as an acoustic underlayment and can be used with a wide range of floor finishes.
An under-screed resilient layer is designed to isolate floor screed from the main structure of the building and the benefit of this means it can deliver a superior impact and airborne sound performance.
Its flexibility ensures it can be used below all types of floor screed developments, helping to deliver compliance with performance standards of the UK building regulations, making it ideal for use in apartments, hotels, schools and education projects, commercial developments, and care homes.
When it comes to modern busy homes, it’s inevitable that some areas experience more traffic than others. These include hallways, where there is a lot of traffic down one narrow path, as well as stairs, where the edge of the carpet on the tread wears quickly. This continuous footfall can unfortunately cause more wear and tear to flooring. It’s therefore important choose an underlay that is durable to protect it.
In addition to this, rooms that feature heavy furniture items can also benefit from a durable underlay. This is because it will be more effective in resisting ‘point loading’, which is when heavy furniture causes irritating indentations in carpets. This is common in dining rooms and lounges, where tables, chairs and sofas can cause accelerated wear and tear.
Crumb rubber is the ultimate underlay product when it comes to durability in any application and out-performs all other underlay types.
An acoustic resilient membrane manufactured from sponge rubber is also a highly durable and versatile underlay which is, long lasting and resistant to foot traffic prior to the floor covering being installed. It can be used as a soft floor covering or as an acoustic underlayment.
There are two main considerations when it comes to selecting the right underlay to use with underfloor heating. Firstly, the tog of the underlay must be below 1.0 to ensure that enough heat gets through to heat the room.
Although a tog of less than 1.0 is normally sufficient, the lower the tog value of the underlay, the better. For underlays that have been designed for underfloor heating in combination with a carpet, a target tog should be 0.8 or less. For underlays for hard flooring, a tog of less than 0.4 is ideal.
The second consideration is the ability of the underlay to withstand the direct heat from the underfloor heating system. Some can end up drying out or crumbling when exposed to heat, which will ultimately cost more time, money, and hassle in the long run. It is therefore crucial to choose the right underlay the first time.
Durability is clearly a priority for floorcoverings in retail and leisure environments, particularly high traffic areas such retail showrooms, hotel receptions, casinos, corridors, and offices.
A key performance enhancer is a good quality underlay, which will protect the floorcovering by absorbing the impact of foot traffic and, in the case of carpet, prevent the pile being crushed and destroyed. This is most easily assessed by looking at the measurements of ‘Work of Compression’ and ‘Compression Under Static Loading’ found on technical specification sheets provided by underlay manufacturers.
Rubber underlays, particularly crumb rubber products which are flat and dense, are good for heavy footfall offering maximum protection and good levels of comfort (and they’re also very good over stair nosings).
A resilient underlay is quick and easy to work with. More often, an underscreed resilient layer is a cost-effective solution for use below all types of floor screeds where pre-completion testing is preferred to that of robust details.
The use of a resilient underlay can contribute to not only the tangible performance of a specified floorcovering, but also the installation’s environmental credentials which are becoming increasingly important particularly in the construction industry.
Given the current war on plastic it’s worth mentioning the green credentials of rubber underlays which are 100% recyclable at the end of their life, with many containing not less than 65% recycled content.