Last edited 26 Jul 2021

Basements in buildings


[edit] Introduction

A basement is part of a building that is either partially or completely below ground level.

Approved document B of the UK building regulations, Fire Safety, Volume 1 Dwelling houses, defines a ‘basement storey’ as ‘a storey with a floor which at some point is more than 1,200 mm below the highest level of ground adjacent to the outside walls.’

The term ‘basement’ is sometimes used interchangeably with the term ‘cellar' and may refer to any sort of below ground space used to provide accommodation, storage, car parking, services spaces, and so on.

However, Approved Document F, 'Ventilation' suggests that, in relation to dwellings, a basement: ' a dwelling or a usable part of a dwelling (i.e. a habitable room), that is situated partly or entirely below ground level.' Whereas a cellar '... is part of a dwelling which is situated partly of entirely below ground level, and is distinct from a basement in that it is used only for storage, heating plant or purposes other than habitation.'

[edit] Recent history

During Victorian and Edwardian times, with cheap labour available, basements were commonly constructed below buildings, but with the onset of the First World War, building rates fell dramatically. After the war the number of houses with servants fell so the requirement for additional accommodation was greatly reduced.

In the 1920s and 30s, with an improvement in public transport, more building land became available and therefore the need to construct basements below the ground almost disappeared.

It is now estimated that less than 2% of new properties are being constructed with basements. However, in cities, such as London, due to the demand for housing, the price of land and the cost of moving, basements are being constructed or converted for living space. This is causing concern in some areas where very large, multi-storey basements are begin constructed, which can cause significant disruption to neighbours over a long period.

See Planning (Subterranean Development) Bill and the Basement Excavation (Restriction of Permitted Development) Bill for more information.

[edit] Benefits of basements

The potential benefits of basements include:

[edit] Downsides of basements

Difficulties include:

[edit] Permissions

[edit] Planning permission

The planning situation will depend on the exact nature of the proposed development and so it is advisable to contact the Local Planning Authority for pre-application advice.

If there is an existing basement that is to be converted into residential space, it is unlikely to require permission. This is assuming that it is not separate to the main dwelling, the usage isn’t significantly changing and a light well is not being introduced.

If a new basement is to be created through excavations involving major work, the creation of separate accommodation or if the external appearance is altered, planning permission is likely to be required.

For works to a listed building, consent is likely to be required.

[edit] Building regulations

For any works to basements or the construction of new basements, building regulations are applicable and will cover areas including ventilation, drainage, ceiling heights, damp proofing, electrical wiring, water supplies, means of escape and so on. See building regulations for more information.

[edit] Party Wall Act 1996

If works are proposed to a property that has adjoining walls or shared walls, the Party Wall Act 1996 may apply. See Party wall act for more information.

[edit] Right of support

Where properties adjoin, there may be a mutual right of support for both land and buildings. This can apply to buildings that are joined, buildings that rely on the support of adjacent land, and to the land itself. This means that if works are carried out to land, buildings, retaining walls, excavations and so on, or if structures are demolished, the right of support of adjoining properties must be maintained.

See Right of support for more information.

[edit] Guidance

The Basement Information Centre contains detailed guidance on many aspects of basement construction, waterproofing and design.

[edit] Restrictions

Concerns about the disruption caused by the construction of basements, and the trend for ever larger 'iceberg' basements in cities such as London have resulted in attempts to introduce restrictions, such as the Basement Excavation (Restriction of Permitted Development) Bill and the Planning (Subterranean Development) Bill.

In August 2016, the City of Westminster introduced a new code of construction practice with an average levy of £8,000 on the construction of basements and a new ‘subterranean squad’ to help reduce the impact of basement construction works.

Deputy leader Robert Davis, said: “We are sticking up for local residents, many of whom have found the explosion of basement development in recent years hellish. It is right that those who want to build basements should contribute to this new service, which will work to help mitigate the negative impacts. Westminster City Council supports the right kind of growth and is not against all basement development, but they must be carried out in a way that is considerate to local residents and the environment.”

[edit] Related articles on Designing Buildings Wiki.

[edit] External references

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