Policy D10 — Basement development

Policy D10 Basement development A Boroughs should establish policies in their Development Plans to address the negative impacts of large-scale basement development beneath existing buildings, where this is identified as an issue locally. 3.10.1 High residential land values and development constraints have led to increasing levels of basement development beneath existing buildings, particularly within central and inner London boroughs. 3.10.2 The construction of basements can cause significant disturbance and disruption if not managed effectively, especially where there are cumulative impacts from a concentration of subterranean developments. Large-scale basements (i.e. those that are multi-storey and/or those that extend significantly beyond the existing building footprint) can cause particular issues, especially when located in residential or higher density mixed-use areas. Such basement development can impact on land and structural stability as well as causing localised flooding or drainage issues. The extent and duration of construction of large-scale basements can also lead to a large number of HGV trips, as well as noise and vibration issues, causing disturbance to local residents. Measures such as requiring Construction Method and Management Plans can help protect neighbours during construction. Other consents and regulatory regimes may also be involved, such as Environmental Health in regard to noise and contamination, and Highways in relation to licences for skips and temporary structures. 3.10.3 The Mayor supports boroughs in restricting large-scale basement excavations under existing properties where this type of development is likely to cause unacceptable harm. Local authorities are advised to consider the following issues, including any cumulative impacts, alongside other relevant local circumstances when developing their own policies for basement developments: local ground conditions; flood risk and drainage impacts; land and structural stability; protection of trees, landscape, and biodiversity; archaeology and heritage assets; neighbour amenity; air and light pollution; and the impacts of noise, vibration, dust and site waste. Where particular and cumulative flood risk issues exist, boroughs should consider restricting the use of basements for non-habitable uses. The Agent of Change Principle ( Policy D13 Agent of Change ) should be applied to basement development to limit the impact of ground-borne noise and vibration from existing uses and infrastructure. Further guidance will be provided in Supplementary Planning Guidance. 3.10.4 Most proposals for the construction of a basement will require planning permission. These proposals need to be managed sensitively through the planning application process to ensure that their potential impact on the local environment and residential amenity is acceptable. 3.10.5 Basement development (small or large) can also cause significant noise and vibration disturbance through the reflection/focusing of ground-borne vibration originating from existing infrastructure, such as London Underground infrastructure, if this issue is not considered and managed effectively during its design and construction. Impact assessments prior to construction should consider the effects on the ground-borne vibration environment and propose appropriate mitigation, especially for surrounding residents. 3.10.6 The Mayor considers that smaller-scale basement excavations , where they are appropriately designed and constructed, can contribute to the efficient use of land, and provide extra living space without the costs of moving house. In areas where basement developments could cause particular harm, boroughs can consider introducing Article 4 Directions to require smaller-scale proposals to obtain planning permission.London Plan Policy D10 · official source →