Plumbing and Heating for London Self-Build Projects: A Practical Guide
Self-build housing projects in London face a distinctive set of challenges compared to those in less densely developed parts of the country, but the number of Londoners undertaking self-build projects on infill plots, garden plots, and replacement dwellings has grown steadily. The plumbing and heating design for a London self-build project needs to be considered from the earliest design stages, as the decisions made at design stage have a significant bearing on the cost, programme, and long-term performance of the building services installation.
Early Design Decisions for London Self-Build Plumbing
The plumbing and heating design for a London self-build project should be developed in parallel with the architectural design from the concept stage, rather than being considered as an afterthought once the structural and architectural design is complete. The routing of soil pipes, waste pipes, and heating flow and return pipework has implications for the structural design, the floor construction, and the ceiling heights throughout the building. A soil pipe that needs to run horizontally for more than a few metres to reach the drain connection point will need a structural void or a dropped ceiling section to accommodate it, and these requirements are much easier to address if they are identified at design stage than if they are discovered after the structural frame has been built.
For London self-build projects, the location and depth of the public sewer to which the new dwelling will drain is a critical early piece of information. The self-builder or their engineer should obtain a Thames Water drainage search and sewer record for the plot before committing to a foundation design, as the sewer location and depth will determine whether the new drainage can connect to the public sewer by gravity or whether a pumped system will be required, and whether a build over agreement or diversion will be needed. In some parts of London, particularly in older residential areas where the sewer network was built in the Victorian period, the public sewer may run through the plot itself or close to its boundary, and this can have significant implications for the foundation design and the drainage layout.
Heating System Choice for London Self-Build Projects
The choice of heating system for a London self-build project should be informed by the energy strategy for the building, the planning conditions applied to the development, and the practical constraints of the plot and building design. For most London self-build projects, the options are a gas-fired combi boiler, a gas-fired system boiler with a separate hot water cylinder, a heat pump with or without supplementary electric heating, or a combination of these technologies. The planning authority may impose conditions on the energy provision, particularly in relation to on-site renewable energy generation or carbon reduction targets, and these conditions should be identified at the planning stage so that they can be designed into the building services specification.
Underfloor heating is a popular choice for London self-build projects because it provides a high-quality heat output at low flow temperatures that are well-matched to heat pump operation, and because it eliminates the visual impact of radiators from the interior design. However, underfloor heating requires a screed floor construction in most configurations, which adds to the floor build-up and affects the structural floor depth and the overall building height. For a London self-build project where the height envelope is constrained by planning conditions, the additional floor thickness required for underfloor heating may need to be traded off against the reduction in ceiling height. Prestige Engineers can advise London self-builders on heating system design, water efficiency compliance, and the Building Regulations requirements for plumbing and heating from the design stage through to final commissioning and handover.
Water Efficiency and Building Regulations for London Self-Builds
London self-build projects must comply with Part G of the Building Regulations, which sets water efficiency requirements for new dwellings. Most London local planning authorities impose the more stringent 110 litre per person per day water consumption standard as a planning condition rather than the 125 litre standard that applies as a minimum under Part G, and the self-builder will need to demonstrate compliance with this standard through the specification of water-efficient sanitary fittings and the submission of a water efficiency calculation to Building Control. The selection of taps, showers, baths, and toilet cisterns should be checked against the water efficiency calculator at design stage to ensure that the planned specification meets the target.
The hot water system for the self-build project must comply with Part G requirements for unvented hot water storage systems if a cylinder is being installed, including the requirement for an expansion vessel, a temperature and pressure relief valve, and a tundish and discharge pipework to a safe location. If a combi boiler is being used, the domestic hot water output and flow rate should be verified against the anticipated demand for the number of bedrooms and bathrooms in the dwelling. The Gas Safe registered engineer installing the boiler or heating system must complete the Benchmark commissioning record, which must be handed over to Building Control on completion of the works as evidence that the heating system has been installed and commissioned to the required standard. Prestige Engineers provide full plumbing and heating installation services for London self-build projects, from first fix through to commissioning and Building Control sign-off.