Soundproofing in older buildings

By Iain Mair

Keeping noise down to an acceptable level in older buildings can be very difficult. Usually, this is due to the fact that the property, be it a family house or converted property, was never constructed to cope with 21st century noise levels!

Before discussing the various ways of dealing with obtrusive noise, it is important to understand the two main types of noise and how they are transmitted through a building’s structure.

“Airborne” Noise
This type of noise can cause the most problems, as the sound waves pass into the structure or through separating layers, such as floors and ceilings. Typical airborne noise sources are hi-fi speakers, human voices, dogs barking and shower pumps, to name just a few. When airborne noise passes through a wall or floor construction, it is known as ‘direct transmission’. When airborne noise bypasses the obvious direct route, and travels down wall lings from floor to floor, for example, this is known as ‘flanking transmission’. Airborne noise can also permeate a building from external sources, especially traffic and aircraft.

“Impact Noise”
Noise generated by impact can be particularly irritating. This is when direct transmission of noise due to footsteps, dropping of items on floors and even utensils on kitchen worktops, causes sound waves to travel. Impact noise is usually not a problem for people living within a single storey dwelling; the problems start when upstairs dwellers start dancing on the floor above! Impact noise can be transmitted easily, particularly on hard existing floors, where every structural element is connected. For example, an upstairs bedroom with bare floor boards fixed to floor joists which are exposed within the lounge below.

Dealing with a noise problem
It is most important to establish the source and cause of the noise. This isn’t always as easy as it sounds, particularly when living in separate flats within a converted property. Sometimes, the noise may sound as if it’s emanating from the flat above, when in actual fact, it’s coming from three floors up, but travelling down the walls!

Many people have failed to deal with noise problems correctly by not establishing the cause. For example, noise through a party wall from one neighbour to another may not always be due to insufficient mass in the wall. It is quite common to find ‘missing bricks’ in the same wall, but below floor level. These may have been deliberately left out for ventilation purposes or pipework etc, but allow noise which passes through the floorboards to travel next door at will.
Noise will usually travel within structures, which makes dealing with the problem ‘at source’ essential, whenever possible. For example, installing a new ceiling below a bathroom with a noisy waste macerator will never be as effective as silencing the macerator in the bathroom itself.

In basic terms, airborne noise can be reduced by increasing the mass of a separating structure (party wall, floor, etc) and by providing isolation and insulation. Impact noise can be reduced by insulating and isolating the noise source.
To simplify matters, let’s look at the two main building types and typical construction scenarios, in brief:

Noise in houses
Many older houses are constructed from relatively lightweight materials such as timber framing with lath & plaster wall linings or stone construction with exposed beams/floor joists. Generally speaking, it will be difficult to deal with airborne noise where direct transmission cannot be easily isolated, particularly where there is a lack of mass, e.g.: a ceiling beneath the floor joists. However, proprietary solutions are available, such as those manufactured by Isomass Ltd, whereby mass & isolation can be applied to existing floor boards, thereby providing a relatively simple solution.

Houses with lightweight wall linings, such as lath & plaster, wattle & daub etc, may suffer with flanking noise transmission. This can be dealt with, but may involve temporary removal of skirting’s and so on, in order to establish the noise leakage routes and provide suitable stopping. The very nature of older, historic buildings means that great care must be taken in doing this type of remedial work, but the results can be very effective.

Many older houses have exposed floorboards on upper floor levels. Due to the fact that they are usually nailed to the joists, the whole floor structure becomes ‘live with noise’ when walked on. Traditionally, laying a good quality carpet or rug over will immediately provide a soft barrier or shock absorber ‘at source’ and thus reduce impact noise transmission. However, many home owners prefer the ‘full wood flooring effect’ and the sound proofing solution must then be provided from within the floor void, (i.e. the gap between the joists) and possibly also the ceiling below.

Noise in flats
Many owners and tenants of older converted properties complain about excessive noise. The problem usually stems from the fact that acoustic regulations did not apply when the building was originally converted and in many cases they are effectively living in a ‘house of multiple occupancy’ with floors and walls which were never designed to act as party constructions.

Floors can be improved by overlaying with proprietary acoustic systems, typically a suitable interlocking deck pre-bonded to a carefully selected resilient layer, or shock absorber. Proprietary acoustic mats are also available for uneven existing floors which cannot otherwise be easily levelled; both options providing a relatively low height increase. As with houses, it is always worth insulating the floor void, using an absorbent product of suitable density, such as mineral fibre.

When access to the noise source cannot be gained, e.g. in the case of an upstairs flat, it is sometimes possible to suspend a totally new ceiling below the original one, in order to provide additional isolation, mass & insulation. However, the loss in both ceiling height and architectural features such as mouldings, etc, is often too much to bear when the noise is emanating from the other flat in the first place
In conclusion, noise can be potentially difficult to deal with unless correctly identified and if possible, dealt with effectively at source. It always pays to seek experienced advice from a knowledgeable firm.

From Listed Heritage magazine