ACOUSTICS

In designing buildings, designers are required to consider the effects of both 'airborne' and 'impact' sound. Airborne sound typically originates from televisions, radios or from human conversation. Impact sound typically relates to noise from footsteps on upper floors or vibration from washing machines and spin dryers. The problem of airborne and impact sound has increased with the popularity of lightweight forms of construction. Also, the current trend of replacing carpet finishes with timber floors has given rise to impact noise problems. Noise between rooms within buildings has also become a greater problem as internal masonry walls have been increasingly replaced with timber stud partitions. The current Building Regulations sound insulation requirements for residential buildings can easily be met by specifying concrete for separating and internal dividing elements.

Sound insulation has become a bigger issue in recent years as higher land prices and changing demographics has lead to increased apartment building with the resultant higher densities and closer proximity of neighbours. The widespread acceptance of loud rock and pop music for recreational purposes and the growing popularity of 'the party culture' as well as the introduction of television and radios in children's bedrooms, petrol lawnmowers, cars and motorcycles, burglar alarms, outdoor parties etc. are just some of the factors giving rise to the increasing problem of noise.

Over the years, concrete-based construction solutions have been used to build all types of residential buildings, from single houses to high-rise apartment blocks. Concrete's inherent properties contribute to good sound insulation which is required to give adequate levels of privacy to the occupiers of houses and apartments.

For detailed guidance reference should be made to the current Building Regulations Part E which deals with the resistance to the passage of sound. Click here

Particular care should be taken to minimise 'flanking sound' transmission by careful attention to details at junctions. Suitable detailing should be identified at the design stage. Even small gaps in the construction of party walls can significantly compromise the sound insulation between properties. For example, care should be taken that joints in precast chimney systems do not compromise the sound insulation of walls between adjoining properties.

Guidance Notes

Note: Those wishing to utilise high quality details to achieve better sound insulation results should refer to the relevant U.K. 'Robust Details'.

Masonry Separating Walls

The following notes are offered as general guidance on workmanship:

Cavity and wall ties should be kept free from mortar droppings and debris
All blockwork joints should be fully filled with mortar
Where two leaf party walls are used, there should be no connection between the two leaves except for wall ties and foundations
Any chases for services should be kept to a minimum and filled with mortar
Appropriate detail selection is required where flues are required in a separating wall
Where render is specified, it should be applied to the complete face of each leaf with a scratch finish (this may be omitted in the joist / beam zone)

Concrete Separating Floors

Precast concrete planks should be butted tightly together and all joint between planks grouted
All voids between walls and floors should be filled
Floating floors and ceiling treatments should be suitable and installed in accordance the manufacturers instructions
Flanking strips around the perimeter of the flooring board should be installed to isolate the floor from the walls and skirtings.
Concrete floor slab density should be suitable for the purpose
The ceiling should not be in direct contact with any steel beams or columns

Floating Floor Treatments

Resilient layers should be installed in accordance with the manufacturer's guidance

Note: Specific guidance on the installation of resilient layers and installing isoRubber is given in the U.K. Robust Details Handbook . Allowable types of floating floor treatments are given on page 17. For details of proprietary acoustic system manufacturers, visit the website, www.pasm.org.uk

Ceiling Treatments

All ceiling joints must be sealed with tape or caulked with sealant. Ceiling treatments must be installed in accordance with the manufacturer's instructions.

Note: Allowable ceiling treatments are given on pages 18 - 21. For details of proprietary gypsum system manufacturers, visit the Gypsum Products Development Association (GPDA) website, www.gpda.org.uk

Downlighters / Recessed Lighting

Downlighters or recessed lighting can be installed in any of the ceiling treatments used in conjunction with concrete floor detailing provided that the minimum ceiling voids given on pages 18 - 21 are achieved and installation is:

In accordance with the manufacturer's instructions
At not more than one light per 2m² of ceiling area in each room
At centres not less than 0.75m
Into openings not exceeding 100mm diameter or 100 x 100mm

Other Concrete Systems

Precast Crosswall: Crosswall construction is a modular Precast concrete construction system. Crosswall creates a cellular structure, frequently used in multi-storey hotels, prisons or accommodation blocks. The components, floors and load-bearing walls, with preformed window apertures, assemble swiftly to form room shells. All internal division walls are manufactured to a high standard of finish. Load-bearing walls are designed as the primary means of support, with longitudinal stability achieved by external walls panels. Crosswall provides a structurally efficient building, with main division walls offering a high degree of sound insulation between dwellings.

Insulated Concete Formwork (ICF): Insulated Cocnrete Formwork is a system where ready-mixed concrete is pumped into hollow walls made from insulation materials which act as a permanent shuttering, offering superior insulation levels. Intermediate concrete floors can be poured at the same time as the walls or precast floors can be installed later. The resulting construction creates a concrete frame building and is ideally suitable for party walls and separating floors between dwellings.

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