Why do most standard walls offer poor levels of sound insulation?

Did you know around three-quarters of the UK’s homes are what we would call ‘connected homes’ – in other words, joined on to at least one other?

According to the Census 2021 data published by the ONS in January 2023, 31.5% (7.8 million) of households were in semi-detached properties, 23.2% (5.7 million) were in terraced properties, and 21.7% (5.4 million) lived in flats, maisonettes or apartments.

It is no surprise that one of the most commonly reported noises is excessive noise from a neighbour’s property. Whilst this could be noise transmitting through a floor below or above with apartments, in the case of many flats and terraced and semi-detached houses this will usually be through a party wall or separating wall.

But why are our party walls incapable of preventing the transmission of everyday sounds such as talking and TVs? There are numerous reasons for this, but ultimately, it comes down to the types of materials used in the construction of UK homes over recent centuries.

Solid brick walls pre-1960s

The most common approach to the construction of walls in the Victorian era right up to the 1950s was to use solid brick. The high mass of these materials might seem ideal for soundproofing in terms of blocking soundwaves. However, the problem with bricks is that they do not cope well with soundproofing against low-frequency sounds which can pass through them easily due to vibration at a certain frequency.

Lightweight walls since the 1960s

As more modern materials rose to prominence in the 1960s, we started to see an increased use of lightweight blocks and timber in the construction of walls in residential properties. These types of construction have less mass or density than solid brick, so many properties built between the 1960s and 2003, when Approved Document E of the Building Regulations for England and Wales was introduced, are similarly prone to noisy neighbour issues.

The Approved Document E era

When Approved Document E was introduced, it was a major improvement to the Building Regulations because it recognised the importance of creating quiet dwellings, as well as thermally efficient and safe. However, the early minimum standards stipulated in the regulations were still far from stringent and, as a result, properties built before the introduction of a major revision in 2010 may also be highly susceptible to neighbour noise through party walls.

Current party wall soundproofing standards

The latest Approved Document E, which relates to the passage of sound in buildings, sets a minimum level of airborne sound insulation for separating walls in residential dwellings of 45 dB DnT,w + Ctr (adjusted for low frequencies). The level of insulation required is slightly higher in Scotland at 56 dB DnT,w (not adjusted for low-frequency sounds).

Whilst it is great to have minimum standards like these, they could be so much better! Approved Document E has not been significantly revised since 2010, despite the advances in acoustic insulation design and materials that have taken place over the last 15 years. Unfortunately, many developers will understandably seek to build only to the compliance level, which is why even many of today’s newly built homes may not offer satisfactory sound insulation.

The good news if you are suffering noise issues from your neighbour’s property is that party walls can be retrofitted with acoustic insulation that will make a difference. Once you’ve identified the wall’s construction materials you can start to explore the options for a sound-reducing design, which could include adding an acoustic lining to a solid brick wall, partially replacing a timber stud wall or constructing a separate acoustic wall away from the existing wall if you have the space.

If you are thinking of adding an acoustic treatment to a party wall it is important to remember that every option will mean increasing the depth of the wall and, therefore, reducing the floor space in the room. Greater depth will provide more sound insulation but the trade-off will be a greater reduction in the room size – so you will need to decide what balance you want to achieve. Your budget will need to be factored into this too.