How to Soundproof a Wall: What Works and What Doesn't

How noise gets through a wall

Voices, TV and music are airborne sound, which Approved Document E describes as sound travelling through the air. It doesn't only come straight through the wall; it finds easier routes too. The building regulations guidance on sound describes two that matter here:

• Air paths: any direct or indirect air passage from one side of the wall to the other.
• Flanking transmission: sound travelling round the wall, through the floor, ceiling and side walls connected to it, instead of straight through (Approved Document E, glossary).

That second one is why soundproofing one wall doesn't always cure the problem: if the noise is also coming through the floor or ceiling, treating the wall alone only helps so much.

What actually blocks sound

iKoustic, a soundproofing supplier, sums up the principles as high mass, absorption and isolation (decoupling). In practice:

• Mass: heavy, dense boards such as acoustic plasterboard. iKoustic's explanation: sound hasn't got enough energy to pass through a high-mass material.
• Decoupling: fixing the new layer so it isn't rigidly connected to the old wall, so less vibration passes from one to the other.
• Absorption in the cavity: acoustic mineral wool between the old wall and the new layer, which stops the gap ringing like a drum.
• Sealing: closing the gaps. Sound Reduction Systems, for example, seals the edges of its boards where they meet the ceiling and side walls.

Two ways to soundproof an existing wall

1. A lining on resilient bars. Resilient bars are thin metal channels fixed across the wall; the new boards are screwed to the bars, not the wall, with mineral wool in between. Sound Reduction Systems, a maker, says this kind of semi-independent lining improved a lightweight block party wall by about 9dB in its own on-site test.

2. A new stud wall in front. A separate metal stud frame built just in front of the old wall, not touching it, filled with mineral wool and boarded with heavy acoustic board. The same maker puts its version at about 17dB better than an untreated masonry wall. It works better because the new wall is fully separate, but it takes more space off the room.

Both start by stripping the wall back, and a bare masonry wall is best sealed with a coat of render first. Then the boards are skimmed and decorated as normal, so expect to redecorate, and to move sockets and switches onto the new surface. Prices for each are on soundproofing costs; a new wall in front is the same kind of work as a stud wall.

Party walls and noisy neighbours

If the noise is from next door, the shared party wall is usually where to start, and it's where most of the improvement figures above come from. A party wall of basic brick or masonry, or a lightweight timber stud, can be improved significantly.

But soundproofing is the expensive answer to a neighbour problem. GOV.UK suggests talking to your neighbour first, then their landlord if they rent, then mediation. If the noise is a statutory nuisance, such as loud music, you can complain to your council, and it's worth getting the council's advice before spending on soundproofing. We'd try those first, and soundproof if the wall itself is the weakness: if you can hear normal conversation through it, no amount of talking will fix that.

What doesn't work

• Egg boxes: they have nowhere near enough mass to block noise, and aren't even good at absorbing it.
• "Soundproof" wallpaper: also too light to block noise from next door. For comparison, one 1.2m by 1.2m acoustic plasterboard weighs about 18kg.
• Acoustic panels and foam: these absorb sound, they don't block it. Approved Document E defines absorption as turning sound energy into heat in a porous material; iKoustic puts the difference simply: absorption makes a room sound clearer, with less echo, while soundproofing stops noise getting in or out. Panels can make a room nicer to be in, but won't stop the neighbours' TV.

Do you need permission?

The Planning Portal says internal alterations shouldn't need planning permission, though a listed building needs listed building consent for significant work inside or out (see soundproofing costs for the rules). If you're building a brand new wall, the Planning Portal says one that separates a bedroom or a room with a WC from another room needs improved sound insulation, and recommends advice from the maker or building control.

Frequently asked questions