Basement schemes draw closer council scrutiny than most residential work: excavation beside neighbouring foundations, spoil removal through residential streets, and months of noise, vibration and dust. Most of the boroughs we work in ask for more than a standard CMP, from engineer-signed method statements to Basement Impact Assessments and building-movement monitoring. Here is what a basement CMP has to cover, and what each borough expects.
A basement CMP covers everything a standard Construction Management Plan does, with the excavation and its effect on neighbouring buildings at the centre. Expect it to set out:
Each borough sets its own basement policy and its own documents. In summary, with the full detail in our borough guides:
Every new or extended basement, of any size, is at least a Level 3 project under the 2026 Code: a CMP with signed Checklist B, approved before work starts, and fortnightly council inspections. City Plan Policy 50 generally limits basements to one storey and to no more than 50% of the garden land.
Basement rules in WestminsterPolicy A5 requires a Basement Impact Assessment, most of them independently audited, and Camden will generally require a CMP, submitted in draft with the application. An Article 4 Direction covering the whole borough means every basement needs planning permission.
Basement rules in CamdenPolicy CD11 limits basements to one storey and 50 per cent of the garden, with no excavation under listed buildings. Applications need a Construction Method Statement signed by a chartered civil or structural engineer and a draft CTMP, and any basement other than a minor one under 50 cubic metres makes the site Category 1 under the Code.
Basement rules in Kensington and ChelseaSouthwark has no stand-alone basement policy, but every new or extended basement needs a Basement Impact Assessment by a suitably qualified engineer or geologist, and the CMP has to carry its monitoring commitments through. No basements are permitted in Flood Zone 3b.
Basement rules in SouthwarkPolicy DH4 requires a Structural Method Statement signed by a chartered civil or structural engineer, and the Basement Development SPD asks for a CMP with the application too. Residential basements are limited to one storey, a 3m floor-to-ceiling height and less than 50% of the original garden.
Basement rules in IslingtonPolicy Q27 requires a Stage 1 Basement Impact Assessment with every basement application. The Basements SPD (August 2023) asks for a draft CMP with the application and a final CMP by pre-commencement condition, reviewed by a suitably qualified and experienced engineer.
Basement rules in LambethThe Local Plan 2031 requires a basement impact assessment for every basement, showing structural stability, safety from flooding and no harm to local hydrogeology, which matters on the Isle of Dogs and in the Lower Lea Valley. Under the Code, basement schemes also need a BS 5228 method statement.
Basement rules in Tower HamletsA borough-wide Article 4 Direction means every basement needs planning permission. Policy DC11 limits new basements to one storey and to no more than 50% of the depth of the garden or host building, and requires a Construction Method Statement by a qualified structural or civil engineer, including a construction traffic management plan, with every application.
Basement rules in Hammersmith and FulhamPolicy LP6 allows a basement only one storey deep and, for homes, under no more than 50% of the rear garden, with stricter lightwell rules in conservation areas and no basements in Flood Zone 3b. A basement in a confined location triggers Wandsworth’s engineer-signed CMP at application stage.
Basement rules in WandsworthPolicy DM18 requires a Basement Impact Assessment with every new basement or basement extension, carried out by independent assessors at the applicant’s cost, and expects the works to minimise noise, vibration and dust and not to harm road safety or bus operations.
Basement rules in HaringeyTwo documents usually come before the CMP. A Basement Impact Assessment tests whether the basement can be built without harm: ground and groundwater conditions, structural stability, flooding and drainage. Camden, Southwark, Lambeth, Tower Hamlets and Haringey all require one. A Construction Method Statement, or structural method statement, explains how the basement will be built and kept stable: Kensington and Chelsea, Islington and Hammersmith & Fulham require one with every basement application, signed by a chartered or qualified civil or structural engineer, and Westminster asks for a structural methodology statement self-certified by a suitably qualified engineer.
The CMP has to be consistent with both. Southwark, for example, expects the Basement Impact Assessment to set out a method for monitoring ground conditions, water movement, subsidence and drainage, and the CMP to carry those commitments through, and Islington requires by condition that the engineer who signed the structural method statement is retained throughout construction.
Basement plans are judged heavily on how neighbours are treated. Westminster strongly encourages consulting neighbours before applying and may ask for evidence, Lambeth’s SPD strongly encourages consulting neighbours and local amenity societies, and Hammersmith & Fulham asks for the Construction Method Statement to be made available to neighbouring owners at the same time as the application. Separately from planning, excavating close to a neighbour’s foundations usually needs notice under the Party Wall etc. Act 1996, and the CMP’s methodology and monitoring should match what the party wall awards allow.
In most London boroughs, yes, in one form or another. Westminster treats every new or extended basement as at least a Level 3 project needing an approved CMP, Camden will generally require one, Islington and Lambeth ask for a CMP with the planning application, and Wandsworth requires one for basements in confined locations. Kensington and Chelsea asks for an engineer’s Construction Method Statement and a draft CTMP with the application, then a Site Construction Management Plan approved before work starts, and Hammersmith & Fulham asks for a Construction Method Statement, including a construction traffic management plan, with every basement application. The conditions on your permission set what has to be approved before work starts.
Lambeth’s Basements SPD gives a typical list: contacts, the programme, working hours, neighbour notification and a 24-hour emergency contact; ground and structural stability, groundwater and movement monitoring, with an engineer inspecting critical works; security hoardings; parking, deliveries, vehicle routing and the cumulative impact of other construction traffic; dust, noise and vibration control, including wheel washing; waste recycling and disposal; and the protection of heritage assets. Other boroughs ask for much the same, in their own format.
Usually a chartered engineer. Kensington and Chelsea and Islington require a Chartered Civil Engineer (MICE) or Chartered Structural Engineer (MIStructE), Hammersmith & Fulham a qualified structural or civil engineer, and Westminster a structural methodology statement self-certified by a suitably qualified engineer, while Wandsworth requires the CMP itself to be signed by a chartered civil or structural engineer. Camden’s Basement Impact Assessments must be prepared by professionals with the qualifications its Basements CPG specifies, and most are independently audited at the applicant’s expense.
Where the boroughs we cover set size limits, they allow one storey, with exceptions on large sites in some, under around half of the garden: no more than 50% of the garden land in Westminster and Kensington and Chelsea, less than 50% of the original garden in Islington, no more than 50% of the rear garden in Wandsworth, and no more than 50% of the depth of the garden or host building in Hammersmith & Fulham. Islington also caps floor-to-ceiling height at 3m, and Kensington and Chelsea and Wandsworth require at least a metre of soil above any part of a basement beneath a garden.
No. A Basement Impact Assessment tests whether the basement can be built without harm: ground and groundwater conditions, structural stability, flooding and drainage. Camden, Southwark, Lambeth, Tower Hamlets and Haringey all require one. The CMP then sets out how the works will actually be run (methodology, programme, hours, traffic, noise, dust and neighbour liaison) and has to carry through the monitoring and mitigation the assessment commits to.