Sump Pump Essential: Rise of Basement Building Despite Flooding Risk!

Installing a basement pump in a UK property should no longer be an unusual or rare event. The requirement for fitting a sump pump – one that is properly specified to correctly and sufficiently deal with the rise of sudden and extreme flooding events – must now go hand in hand with basement building plans, also a deepening trend.

Planning applications for basement building increased by 9 per cent over 24 months, according to recent data from national home insurance providers. The Environment Agency has also warned that one in six properties (around 5.2 million) in England are at risk of flooding. An estimated nearly three million properties across the country are vulnerable to surface water flooding caused by heavy rainfall overwhelming local area drainage capacity or blocking sewer pipes.

Popularity of “building down”

In London and the South East, overcoming limitations attached to planning applications for extending a property outwards has led to the popularity of “building down” and creating a basement space. In 2017, latest available figures show that the number of applications for basement building in London alone, increased from 1,348 to 1,497. Nearly three quarters (72 per cent) of applications – around the national average – are normally accepted.

In a ten year period up to 2017, seven London boroughs including, Camden, Hammersmith and Fulham, and Wandsworth had been given planning permission to build 4,650 basement developments. Over three quarters (81 per cent) were standard, single-storey excavations but more than one in six (17 per cent) were more larger-scale two-storey constructions.

Basement building is not confined to the capital. Economic uncertainty causing property price growth slowdowns and a lack of sufficient house building across the UK has also led significant numbers of homeowners to “stay put” and extend their property instead. Adding a basement to an average, residential two-storey house can extend its floor area by up to 50 per cent without increasing a property’s footprint or reducing garden space.

South East in high risk category

Some homeowners living within city centres or residential suburban areas may consider their risk of local flooding as minimal or even non-existent. However, the Environment Agency state that the Greater London area contains more than half a million properties –  around one million people – located on a floodplain, with around 100,000 at “significant” risk of flooding.

However, the number of properties in areas with a “significant” chance of flooding are highest in south east England,  which has 25,000 more properties – around 64,000 people – in the high risk category. More than a quarter of a million properties in the south east are also at a “moderate to high risk” of a flood event.


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