Plumbing Requirements When Changing Property Use in London
Changing the use of a London property from commercial to residential, or from one type of residential use to another, triggers a set of plumbing and building services obligations under the Building Regulations and associated legislation. Understanding what is required before committing to a change of use project helps London developers and investors avoid costly surprises during the construction programme and at the point of Building Control sign-off.
Building Regulations and Change of Use in London
A change of use application in London does not simply require planning consent from the local authority. It also triggers a requirement to comply with the current Building Regulations, which means that the property must be brought up to the standard required by those regulations as they apply to the new use. For a commercial building being converted to residential use, this means that Part G of the Building Regulations, which covers sanitation, hot water safety, and water efficiency, must be satisfied for every new dwelling created. Similarly, Part L requirements for energy efficiency and heating systems will apply, and Part P requirements for electrical installations will need to be addressed alongside the plumbing works.
In London, where a significant proportion of change of use activity involves the conversion of office buildings, retail units, and light industrial premises to residential flats under permitted development rights or full planning permission, the plumbing implications are substantial. An office floor that contained a small kitchen and a few toilet cubicles to serve a hundred workers will need to be completely replumbed to provide individual bathroom and kitchen facilities for perhaps ten or twenty new dwellings, each of which must comply with the water efficiency requirements of Part G and must have adequate hot water provision and heating to the standard required by a building intended for human habitation.
Water Supply Requirements for Changed-Use London Properties
The cold water supply to a London property being converted from commercial to residential use will almost certainly need to be upgraded. Commercial buildings are typically served by a mains water connection sized for periodic high-demand use from toilet cisterns and a small number of hot water points, and this connection may be inadequate to supply the simultaneous demand from bathrooms and kitchens in multiple new dwellings. A hydraulic analysis of the cold water demand for the proposed residential use should be carried out at design stage to establish whether the existing connection size is adequate, whether a new or upgraded connection from the main is required, and whether internal distribution pipework needs to be redesigned to serve the individual dwellings.
Thames Water, which supplies water to most of London, requires a formal application for a new or upgraded connection and will assess the impact of the new demand on the local network before approving the connection. For larger change of use schemes creating multiple dwellings, the connection application process can take several weeks, and this should be programmed into the project timeline. Individual water supply connections to each dwelling, with separate metering where required by Thames Water or the local planning condition, may also need to be specified at design stage so that the pipework routes are accommodated in the building structure. Prestige Engineers can advise on the cold water supply design for change of use projects across London and can manage the Thames Water application process on behalf of clients.
Drainage and Sanitary Requirements for London Change of Use Projects
The drainage requirements for a London change of use project depend heavily on the existing drainage infrastructure and the scale of the new residential use being created. Where an existing commercial building had limited sanitary facilities, the foul drainage from the building may have been routed to a single connection point on the public sewer, and this single connection point may have insufficient capacity or be in the wrong location to serve a residential scheme with multiple bathroom and kitchen drainage points on each floor. A drainage survey of the existing system, including a CCTV survey of the drain runs and a check against the Thames Water sewer map to establish the location and size of the public sewer, should be carried out before the plumbing design is finalised.
Where an existing building drains through pipework that passes beneath a neighbouring property or beneath a public highway, or where new drainage routes need to be established to serve a residential conversion, build over agreements or highway crossing licences may be required. Each new dwelling must have adequate provision for sanitary drainage from toilets, baths, showers, washbasins, and kitchen sinks, and the drainage design must demonstrate that all drainage is by gravity where possible, with mechanical pumping systems used only where gravity drainage is not achievable. Prestige Engineers carry out drainage surveys, drainage design, and full plumbing installations for change of use projects across all London boroughs, and can co-ordinate the Building Control notification and inspection process from start to completion.