How to Enhance Sound Insulation with Cement Board 

27th Jun 2024 -

Sound insulation continues to be an important consideration for all residential and commercial spaces. The ability to control and mitigate unwanted noise is key to creating comfortable and functional environments. A solution that has gained traction in recent times is the use of cement board. 

For this feature, we look into how cement board is being utilised to boost acoustic insulation. We explore the properties and installation techniques of cement boards, highlighting their effectiveness in enhancing sound insulation.

What is Cement Board?

Cement boards consist of a core made from cement reinforced with fibreglass mesh or strands. The core is placed between 2 layers of fibre cement sheets or between a fibre cement sheet and fibreglass mesh. 

The cement core provides excellent strength, durability and resistance to moisture and fire. This makes cement board an ideal choice for various applications in both interior and exterior settings.

Common applications

• Tile substrate: A common use as a substrate or backer board for ceramic, porcelain and stone tile installations. Its moisture and mould resistance make it perfect for areas such as bathrooms and kitchens.
• Exterior cladding: They can be used as an exterior cement board cladding material for buildings, providing a durable and weather resistant surface. 
• Flooring underlayment: Cement boards serve as a stable and moisture resistant underlayment for various types of flooring, including tile, vinyl and laminate.
• Acoustic insulation: The high density of cement board makes it an effective material for improving sound insulation in walls, ceilings and floors.

Types of cement board

• Regular cement board: The most common type of cement board, typically composed of a cement core reinforced with fibreglass mesh. It has a smooth surface on one side and a rough texture on the other.
• Fibre cement board: Similar to regular cement board but incorporates cellulose fibres in addition to the cement core and fibreglass reinforcement. Cement fibre board is often used for exterior fibre cement cladding because of its enhanced weather resistance.
• Lightweight cement board: Lightweight cement board is a lighter version of regular cement board, making it easier to handle and install. However, it may not offer the same level of durability and strength as its heavier counterparts.
• High-performance cement board: This type offers superior moisture and mould resistance. It is ideal for high-moisture environments like steam rooms.
• Tile backer board: Also referred to as cement backer board. Tile backer boards are designed as a substrate for tile installations. It has enhanced moisture resistance and a rough surface texture for better adhesion for the tile mortar.
• Cement particle board: Made from a mixture of cement and wood particles, offering a balance between the properties of cement and wood. It is typically denser than a regular cement board, providing good sound insulation and fire resistance. Cement particle board is often used in flooring, wall sheathing and roof decking applications. 

Is Cement Board Fully Soundproof?

While cement board is effective at improving sound insulation, it is not entirely soundproof. However, certain types like cement particle boards enhance acoustic performance and reduce noise transmission.

To measure soundproofing capabilities, sound ratings like sound transmission class (STC) are used. Regular cement board typically has an STC rating of around 35-40, which is considered moderate for sound insulation. However, cement particle boards can achieve STC ratings of 45-50, providing significant noise reduction.

Learn more about sound ratings with our detailed guide.

How to Boost Cement Board Acoustic Performance

Several techniques can be employed to further enhance acoustic insulation. By incorporating specialised materials and methods, you create structures that offer improved noise reduction and sound isolation.

Staggered stud framing

Instead of traditional stud framing, using staggered stud framing may improve sound insulation. This involves staggering the studs on opposite sides of the wall, creating an offset pattern that breaks the direct path for sound transmission. Combined with cement board and insulation, staggered studs create multiple air pockets that disrupt sound waves and reduce flanking noise.

Resilient channel installation

Resilient stud channels detach the cement board from the framing, reducing the transfer of vibrations and improving sound insulation. They are particularly effective in combination with soundproof cement boards for enhancing both airborne and impact noise reduction.

Insulation

Incorporating insulation like mineral wool or fibreglass batts further enhances sound insulation. The insulation material helps to absorb sound energy and reduce sound transmission. It is important to ensure proper insulation installation without gaps or compression for optimal acoustic performance.

Floating floor systems

For floor assemblies, installing a floating floor system with cement board can reduce impact noise transmission. This involves creating a separate floor layer over the subfloor using resilient underlayment and cement board. It effectively detaches the flooring from the structural elements and reduces vibrations.

Mass-loaded vinyl (MLV) barrier

MLV is a heavy, limp and dense material that is highly effective at blocking airborne noise transmission. It can be installed between studs and the cement board or even as an added layer over the cement board. As a result, it creates a highly effective sound barrier.

Does Cement Board Thickness Affect Sound Insulation?

Cement board thickness plays a significant role in its sound insulation properties. Generally, thicker cement boards provide better sound insulation than thinner ones. This is because doubling the mass of a barrier equals an estimated increase of about 6 decibels (dB) in sound transmission loss.

1/4 inch (6.4 mm)

The thinnest commonly available cement board is widely used as a tile backer in bathrooms and kitchens. It is lightweight and easy to handle, providing basic moisture resistance. However, a 6mm cement board offers limited sound insulation. It has an estimated STC rating of 26-30 and is less rigid compared to thicker options. 

⅜ inch (9.5 mm)

A versatile thickness used for both wall and floor tile installations, as well as some exterior applications. It offers a good balance between weight and performance, with improved rigidity over ¼ inch boards. Also, it provides moderate sound insulation with an STC rating of around 30-35 and is suitable for home tile projects.

½ inch (12.7 mm)

Widely used for interior walls, ceilings, and exterior applications such as siding underlayment. This thickness provides excellent strength, good sound insulation with an STC rating of around 35-40 and high moisture resistance. Suitable for residential and commercial use in spaces like bathrooms, utility rooms and shared walls in apartment buildings.

⅝ inch (15.9 mm)

Often used in commercial construction. It offers high impact and fire resistance and enhanced sound insulation with an approximate STC rating of 40-45. This thickness delivers an excellent substrate for large-format tiles. It is best suited for commercial buildings, multistory structures and areas requiring higher fire protection.

¾ inch (19 mm)

This is a thicker option particularly suitable for flooring underlayment in commercial settings. It offers maximum strength and high sound insulation with an STC rating potentially exceeding 45. Also, it works as an excellent substrate for natural stone or large-format tiles. 

Shop various cement board thicknesses with our range. 

Can You Render Cement Board for Sound Insulation?

Rendering over cement board potentially enhances sound insulation. It combines the strength and moisture resistance of cement board with the durability of render. This may improve the overall acoustic performance of a wall structure. Rendering can improve sound insulation through several points.

• Increased mass: Adding a layer of render increases the overall mass of the wall assembly. The added mass may enhance sound insulation, particularly for mid to high-frequency sounds.
• Damping: The render board layer acts as a damping material. It helps to break up sound energy as it passes through the wall assembly.
• Reduced resonance: The combination of cement board and render creates a composite material with different resonant frequencies. This potentially reduces the overall sound transmission across a broader frequency range.
• Airtight seal: A well-applied render finish creates an airtight surface, minimising sound leaks through small gaps in the cement board installation.

The degree of sound insulation improvement relies on various factors.

• Render thickness: Thicker render applications generally provide better sound insulation. A 15-20 mm layer of render could increase the STC rating by 3-5 points.
• Render density: Denser render materials, such as traditional sand and cement renders, may offer better sound insulation than lighter acrylic options.
• Application quality: Proper application technique ensuring full coverage and good adhesion is crucial for optimal acoustic performance.
• Overall assembly design: Improvement will be most noticeable when rendering is part of a well-designed acoustic assembly. This includes proper framing, insulation and other sound-reducing techniques.