Hush Acoustics: When do you need to use Hush Slab?

  • 7 Mar 2024

Any separating floor, ceiling or wall that features a void can benefit from an acoustic upgrade using the class A1 fire rated Hush Slab sound insulation slab from Hush Acoustics

Supplied in slabs sized 1200mm x 600mm, this acoustic mineral wool product has been developed specifically to reduce airborne sound transmission through separating floors, ceilings and walls within both new build and refurbishment projects, with four thicknesses available to suit the vast majority of applications. 

This includes timber joisted floors and metal or timber stud separating walls and in suspended ceilings below timber or concrete/masonry floors, such as where a metal frame (MF) ceiling system is deployed. As a result, Hush Slab is widely used in the fully tested, Building Regulations compliant acoustic systems developed by Hush Acoustics.

Other uses

But these are not the only ways Hush Slab can be used. In addition to the wall and floor constructions separating individual properties, which are subject to more demanding minimum acoustic performance standards under the Building Regulations, including Approved Document E in England & Wales, Hush Slab can also be used with internal timber stud walls and timber joisted floors in residential buildings. 


Fitting it in these constructions rather than leaving voids empty can be an effective way to reduce sound transmission between rooms such as home offices, studies, bedrooms, bathrooms and media or cinema rooms. Sound reduction inside our properties has become a significantly more important issue in recent years due to changes in the way we use our homes.


Hush Slab is manufactured using a unique process which utilises renewable energy and a sustainable source of raw material, making it ideal for use in low carbon building projects. It is also a highly durable material that will not degrade over time thanks to its non-hygroscopic inorganic rock composition, which also means it will not encourage the growth of fungi, mould or bacteria, sustain vermin or rot, and it is odourless.

It is an ideal choice for acoustic floors/ceilings and party walls where sound reduction goals must be achieved whilst complying with fire protection requirements, and meet thermal performance targets. These triple benefits stem from its fibrous nature which is created by the stone wool manufacturing process, resulting in a non-directional fibre orientation and density that disrupts, traps sound waves and dampens vibrations.


Being class A1 rated for fire performance means the material is capable of withstanding temperatures in excess of 1000°C, meaning it is regarded as completely non-combustible. And thermal performance is excellent too, thanks to Hush Slab 100’s thermal conductivity of 0.035 W/mK and thermal resistance of 2.85 W/m2K.

Which thickness of Hush Slab should I use?

When it comes to sound reduction, the more density within a floor/ceiling or wall structure you can add the better. Thicker layers of insulation offer the highest acoustic insulation which is why the optimum thickness of Hush Slab is 100mm –referred to as Hush Slab 100.

However, it is not always possible to use Hush Slab 100 due to constraints in the depth of the void, particularly in refurbishment projects. Hence why there are three other thicknesses of Hush Slab – 75mm, 50mm and 25mm – to give architects and contractors the scope to upgrade acoustic performance in the majority of applications.


For example, if you are adding a wall lining to an existing masonry wall, you may want to minimise the depth of this in order to preserve as much floor space in the room as possible. Whilst the trade-off for this will be a lower level of acoustic performance, being able to make improvements to sound control using one of the thinner versions of Hush Slab is often appealing to homeowners or tenants because it achieves an excellent balance.

Ultimately, the thickness you choose depends on the application – the thicker, the better for acoustic insulation, but all four thicknesses are guaranteed to make a difference.

Find out more about Hush Slab at

Hush Acoustics Ltd
Unit 2, Tinsley Industrial Estate
Shepcote Way
South Yorkshire
S9 1TH

Tel: 0114 551 8685
Fax: 0151 944 1146

Visit Hush Acoustics' website

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