Beginners Guide to Acoustic Underlay Flooring in 2023

Soundproofing your home is a luxury, but more often a legal necessity. This is especially true if you live in apartments and townhouses which enforce strict body corporate / strata policies regarding noise levels.

Installing flooring without abiding by the strata requirements can result in very very expensive repercussions – you’ll be forced to rip up all the floors and install the right underlay.

Not all underlay are created equal – but that’s ok, this article will explain to you how underlay works, and how to determine which underlay you need.

What is flooring underlay used for?

Flooring noise reduction is primarily achieved through the use of an acoustic underlay. Installers will need to lay rolls or sheets of underlayment over the subfloor before installing floating floorboards on top. Think of underlay as a layer of foam or rubber material that cushions any impacts and blocks loud noises. 

Acoustic engineers determine the effectiveness of flooring underlay by testing the underlay in-situ against noises. Although underlays are primarily designed for noise reduction, they can also function in a wide variety of applications:

• Impact Noise – Sounds caused by direct footfalls, thumping and dragging furniture.
• Ambient Transmission – Sound from televisions, chatter and other indirect noise in the air.
• Moisture Protection – Can act as a moisture barrier to protect your wood floors.
• Insulation – Can provide thermal insulation, keeping your summers cooler and winters warmer.
• Comfort – Can increase the comfort underfoot by making each step feel less hollow.
• Subfloor Levelling – Thicker underlayment can be used to help level uneven subfloors in some cases. (not always suitable for this purpose)

Types of Flooring Underlay Available

There are many types of underlay in the market with different levels of acoustic protection. This is measured in AAAC Star Ratings, from 1 star at lowest up to 6 stars which is the highest. Flooring acoustic standards are determined by the National Construction Code (Previously known as Building Codes Australia).

If acoustic underlay is required, it will be at least 4 stars or above. Most apartments, units and townhouses require a 5 star rating. Some more stringent areas will demand 6 stars or a certain thickness.

Silver EPE foam underlay is by far the most commonly used option. Whilst it offers no significant ‘Acoustic’ protection, the waterproof film and 2mm foam composition function to protect your floors from moisture and movement.

Gold EPE foam underlay is 3mm thick, offering a slightly higher acoustic protection than the general silver option. This is considered the ‘Level 2’ version of non-acoustic underlay, offering slightly better performance.

The ‘EveQuiet Green Acoustic’ underlay is the most basic option for noise protection. Offering 4 star acoustic protection, they serve very well in most units and apartments.

Of course, there are many more options ranging from Regupol’s rubber range to Dunlop’s ‘Aquacoustic’ underlayments, offering 5 and 6 star acoustic protection alongside a variety of other benefits. If you are looking for a specific brand, don’t hesitate to reach out to one of our friendly flooring consultants.

Cost of Underlayment

The real question is whether or not the cost of purchasing underlay will significantly impact your flooring project. The price per square metre generally increases with the number of AAAC Star Ratings an underlayment has. However, this is not always the case. The prices of underlay in Sydney as of 2021 are provided below:

• General Foam Underlay 2mm: $2 – $4 per square metre
• 4 star Acoustic Underlay: $5 – $10 per square metre
• 5 star Acoustic Underlay: $10 – $20 per square metre
• 6 star Acoustic Underlay: $20 – $30 per square metre

The most expensive flooring underlay options can range up to $100 per square metre, however they are incredibly uncommon requirements. The vast majority of flooring underlay requirements will not exceed $15 per square metre, so rest assured it probably won’t eat into your bank.

How to determine your underlay requirements

Now that we understand how floor soundproofing works, let’s find out how to determine whether or not you will need flooring underlay. How do you know if you need underlay, and if you do, how do you know which you need?

• Are you living in a home or an apartment/unit/townhouse? If so, there is a 99% chance you will need some form of underlayment for your flooring.
• You will need to contact your strata by email regarding acoustic underlayment for flooring if it is required. They will likely provide you with information regarding a required underlay thickness, an AAAC rating or a specific type of underlay.

Floating Floor Underlay

Only floating floors require an underlay. Floating floors are a group of flooring types that do not require glue or nails during installation, and are instead ‘floated’ on top of the subfloor. To put it simply, we do not directly nail or glue them into the subfloor. Floating floors include laminate flooring, bamboo flooring, hybrid flooring and engineered timber flooring.

If you are looking to install solid timber into your floors with direct-stick to the subfloor, underlay will not be required. This scenario can arise if you do a glue-down installation of solid timber into your apartment since the strata does not allow noisy nail banging.

Hybrid Floors and Pre-attached Underlayment

Most (not all) hybrid floors come with pre-attached underlay which have AAAC Rating certifications. This means you won’t need to add additional underlay if it already meets strata requirements. 

For example, FloorVenue stocks Marvel SPC Hybrid flooring which has a 6 star acoustic underlay pre-attached. Marvel hybrid floors can virtually be installed anywhere since it has the highest acoustic certification without the need for additional underlay. (Unless the strata demand a certain underlay thickness regardless of AAAC rating)

Technical Flooring Underlay Details

AAAC star ratings are essentially simplified abbreviations for the level of decibel reduction from noise. This technical measurement of underlay performance is measured in LnT,w.

LnT,w – LnTw is the weighted, standardised impact sound pressure level of a floor assembly. The lower the LnTw value, the better the acoustic performance. This is measured in decibels (dB).

• 2 Star acoustic rating – LnT,w < 65 dB
• 3 Star acoustic rating – LnT,w < 55 dB
• 4 Star acoustic rating – LnT,w < 50 dB
• 5 Star acoustic rating – LnT,w < 45 dB
• 6 Star acoustic rating – LnT,w < 40 dB

Testing Conditions:

The AAAC rating of underlay is tested on-site with various types of flooring, the specific underlayment, concrete subfloor (150mm – 200mm) and a ceiling cavity to replicate a real-world scenario. Noise insulation is measured by direct impact sources as well as ambient noise from 50 – 10000 hertz.

The underlayment requirements depend on the building classification which comes in 10 classes. These adhere to the National Construction Code (NCC).

Conclusion – What Are Your Next Steps?

Hopefully, this guide was about to assist you in determining whether or not underlay will be required. If you have any questions, queries, comments or complaints – don’t hesitate to reach out. FloorVenue stocks and supplies a multitude of underlay and our friendly consultants have extensive product knowledge. We’ll definitely be able to help you make the right decisions.