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Chimney breast

How do you soundproof a chimney breast?

If you live in a property – or if you are working on one – with a party wall that features a chimney breast and alcoves, you might be wondering if anything can be done to improve soundproofing that cuts noise transmission from the neighbouring property.

The most common situation we see is a party wall, separating terraced or semi-detached houses, with a chimney breast positioned somewhere near the middle, leaving two alcove spaces to the side. This usually means the alcove walls are more susceptible to sound transmission than the chimney breast, because of the large difference in the thickness of the party wall at those points.

The priority then, in the vast majority of cases, to upgrade the sound insulation on the alcoves rather than the chimney breast itself.
However, that does not mean there is never a need to treat the chimney breast. If a neighbour has removed their chimney breast and, perhaps, fitted a wall mounted television where it used to be, nuisance noise may start to be heard through the much thicker construction. In such cases you should consider the options for treating the whole party wall should you space allow you to do so – chimney breast and alcoves.

Is the chimney still in use?
How to decide on altering the room space
What building materials to use to soundproof the chimney stack
How do you know if your sound insulation combination will work?
Should you soundproof the ceiling?

Is the chimney still used for the fire or stove?

If the fire is still active, such as with a fully operational gas fire or wood burning stove, any treatment of the chimney breast will need to consider fire safety risks. Many of the products used for soundproofing are unsuitable for use so close to a naked flame and heat, so please talk to the acoustics specialists at Hush Acoustics before pressing ahead with your sound insulation plans.

How much room space are you prepared to lose?

Adding soundproofing to an existing wall will involve installing materials onto the surface of the wall, which adds to the wall thickness – this will encroach into the floor space and make the room slightly smaller. So ask yourself how much space you can afford to lose – there are slim and standard wall treatments available to help you.

Which products and systems will soundproof a chimney breast and alcoves?

When adding soundproofing to a party wall of any kind, the goal is to stop sound transmission paths through the various materials used. This will require a combination of adding high mass materials to block sound waves and absorption materials that will convert the sound energy into heat.

Materials such as soundbloc acoustic plasterboard and Hush Acoustic Wall Board add mass and density, the latter being manufactured using two deadening boards separated by visco-elastic dampening strips. The dampening strips decouple one side of the board from the other, reducing direct transmission paths and reducing airborne noise transmission through a wall construction.

But products like this will not be effective unless they are used in combination with materials that can absorb sound energy and vibrations. These include products such as Hush Slab 100, a mineral wool sound absorber slab, along with Hush Bar Deep resilient bars and Hush Isolation Tape which help to provide separation between materials.

How do you know if your sound insulation combination will work?

The best way to achieve the soundproofing results you are seeking is to install a fully tested acoustic system from Hush Acoustics. Two systems in particular are ideal for soundproofing a chimney breast wall to deliver excellent performance.

The HD1055 is designed for a masonry wall, providing a stud lining with a depth of 150mm. It is created by constructing a single frame of 50 x 100mm timber stud work independently from the existing masonry wall with a clear 25mm gap.

Hush Acoustic Party Wall Solution using building materials

The floor and ceiling structure is isolated from the studwork using the Hush Heavy Duty Isolation Tape, and the stud is insulated using Hush Slab 100 sound absorber, tightly fitted within the voids and ensuring the gap to the masonry wall remains clear. The masonry side of the new timber frame is faced with two layers of 15mm Soundbloc plasterboards and the perimeters are sealed with the Hush Acoustic Sealant.

A slimmer option is the HD1041 wall lining system. This uses a different combination of materials to reduce the overall thickness to just 60mm, with a slightly lower performance level. It is a compromise that many Hush customers are happy to make in order to maintain floor space, particularly in smaller rooms.

How to soundproof a party wall diagram

This system combines 15mm Fireline plasterboards with the Hush-Multi Panel, sealed at the perimeters using Hush-Isolation Tape and Hush Acoustic Sealant. Both boards are fixed to Hush Deep Resilient Bars and the voids created are filled with Hush-Slab 25 sound absorber panels.

Are you able to treat the ceiling too?

Adding an acoustic wall system such as HD1055 or HD1041 will definitely reduce the amount of sound transmitted through a party wall, so you will notice an improvement. However, sound waves will always find a way around, which we call ‘flanking’, such as through the ceiling that is connected to the party wall.
The good news is that you could add an acoustic ceiling system at the same time to further reduce sound transmission from next door. Hush Acoustics offers a variety of systems which are extremely effective.

However, remember that treating the ceiling will affect the whole room so you need to consider whether that is feasible given the need to change décor and the disruption of the work.

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