Comparing Subfloor Systems

This article reviews five common subfloor systems and compares their effectiveness when it comes to 10 key features.  These important features are of significant value to home-owners and include cost effectiveness, fire and moisture resistance, thermal and acoustic performance as well as environmental impact.

Why do I need a subfloor?

Subfloors are often used when it is not desirable, viable or possible to have a concrete slab floor. The two most common examples of this are:

1. Multi storey builds or extensions; and
2. Modular or elevated builds

There are several different types of subfloor systems available for multi storey builds and the subfloor you choose can have a significant impact on the people who live in the dwelling.

1. Multi Storey Builds and Extensions

In most multi storey residential projects, the subfloor system sits above the main structural part of a floor and below the decorative floor covering. There are several different types of subfloor systems available for multi storey builds and the subfloor you choose can have a significant impact on the people who live in the dwelling.

2. Modular and Elevated Builds

Modular and raised homes are normally built on stumps where there is uneven or sloped terrain. It is also common to have elevated floors in areas that have reactive soils because a concrete slab would not be suitable in these conditions. A beam and joist system is then installed on top of the stumps and becomes the frame that supports the subfloor.

What are my subfloor options?

Here is a comparison of five of the most common subfloor systems including those that have been used for decades through to the newer, more environmentally friendly solutions.

1. Composite Flooring Panel System (SUPAFLOOR)
2. Particleboard (Chipboard)
3. Autoclaved Aerated Concrete (AAC)
4. Compressed Fibre Cement (CFC)
5. Concrete Truss & Suspended Concrete

1. Composite Floor Panel System (SUPAFLOOR)

SUPAFLOOR is a subfloor system that has been developed in Australia and has an insulative core which is sandwiched between two layers of SUPABOARD technology. This SUPABOARD material is environmentally friendly as it is made from naturally occurring minerals, does not require heat or pressure during manufacturing and is 100% recyclable. It is also resistant to moisture and fire and can be used in areas with reactive soils, which makes it ideal for elevated subfloor systems as well as multi storey builds and extensions.

Since it is water resistant, SUPAFLOOR also comes with two different thicknesses to automatically account for the wet area set down requirement

The insulative core makes SUPAFLOOR a lightweight and easy to handle panel system which decreases build times, while also providing excellent ratings when it comes to thermal efficiency and acoustic performance. Since it is water resistant, SUPAFLOOR also comes with two different panel thicknesses to automatically account for the wet area set down requirement, making it a complete subfloor system. Importantly, SUPAFLOOR is very cost effective and once installed can be easily finished with direct stick timber, carpet, stone, vinyl and even tiles without the need to screed.

2. Particleboard (Chipboard)

Particleboard or chipboard flooring is a popular option as it is cheap, light weight and fast to install. While those benefits can provide a positive outcome for builders, they do not always translate to a pleasant experience for home occupiers. Particleboard is not very effective when it comes to thermal or acoustic insulation and this can reduce the property value of both elevated and multi storey homes.

Finally, particleboard does not have a strong structural feel underfoot, nor does it have a high fire resistance level.

Without this subfloor insulation, elevated homes are exposed to outside temperatures from underneath while occupants of multi storey dwellings can be disturbed by sounds coming from other levels. Finally, particleboard does not have a strong structural feel underfoot, nor does it have a high fire resistance level. These structural concerns must be strongly considered on a par with any potential cost savings if you are weighing up chipboard as a subfloor option.

3. Autoclaved Aerated Concrete (AAC)

For over 70 years, concrete has been combined with a foaming agent inside a mould to create the product known as Aerated Concrete. Soft panels are then cut from this mould and need to be hardened. This hardening is achieved by cooking the concrete panels with steam (autoclaving) inside a chamber at nearly 200℃ for 12 hours. The benefits of AAC for use as subfloors have traditionally been praised when compared to standard concrete. These advantages over concrete include; increased thermal efficiency, workability with lightweight panels, more environmentally friendly and longer lasting with less chance of cracking.

The benefits of AAC for use as subfloors have traditionally been praised when compared to standard concrete.

However, when compared to more modern technologies such as some composite floor panel systems, AAC matches them with a strong structural feel and acoustic performance but has been surpassed in other areas. Modern composite subfloor panel systems are half the weight, have twice the thermal efficiency, come in larger panels, are less brittle and more environmentally friendly than AAC. Another noticeable difference is that AAC is not water resistant and has been known to crack when installed in rainy weather where modern composite floor panel systems are water resistant.

4. Compressed Fibre Cement (CFC)

Compressed Fibre Cement is a composite of cement, water, cellulose fibres and finely ground toxic silica. It is produced into sheets and then compressed to a very high density before being hardened with high pressure steam (autoclaved). CFC is strong, durable and fire resistant but doesn’t perform so well acoustically and thermally when compared to other types of subfloors system.

While being reasonable priced, CFC is still more expensive than modern alternatives and the sheets are up to 25% heavier

Even though it doesn’t have the strongest structural feel, it is water resistant which makes it suitable for use in wet areas which aids with planning and construction. While being reasonable priced, CFC is still more expensive than modern alternatives and the sheets are up to 25% heavier while having a higher environmental impact during manufacturing.

5. Concrete Truss & Suspended Concrete

A suspended concrete subfloor involves pouring concrete onto sheets of corrugated iron that have been laid out on a steel truss system. This type of subfloor has the same solid feel as a conventional concrete slab floor but is cheaper and faster to install. Just like Aerated Autoclaved Concrete, it looks very impressive when stacked up against traditional concrete floors, but it lacks the benefits of the more recently developed subfloor systems.

Suspended Concrete lacks a low-density layer to absorb noise as well as other products on the market do, so it can carry sounds through to the level below.

Suspended Concrete lacks a low-density layer to absorb noise as well as other products on the market do, so it can carry sounds through to the level below. It also has a much higher price point and lacks thermal efficiency while its complex design means it takes much longer to install and has a higher environmental impact than some composite floor panel systems.

Conclusion

It’s hard to go past modern technologies such as SUPAFLOOR when it comes to choosing a subfloor for an elevated or multi-storey building project.  While the three concrete based flooring solutions have traditionally had a few key strengths, there are now more features available for home owners to carefully consider.  Particleboard is a low cost option but it lacks most, if not all of the features offered by SUPAFLOOR and most notably does not have a strong structural feel.  SUPAFLOOR also wins big with the environment with not only its manufacturing process, but its built-in thermal efficiency means it will satisfy building code standards and reduce the need for additional insulation materials.

Written by Matthew De Pledge