Pre-Construction Information in London: What It Is, What It Contains, and Why It Matters

The Construction (Design and Management) Regulations 2015 (CDM 2015) impose a duty on the client (in a domestic construction context, typically the homeowner) to ensure that pre-construction information is assembled and provided to every designer and contractor before design work begins and before construction begins.

Pre-construction information (PCI) is the body of information relevant to health and safety that already exists about a site and a project before the build commences. Its purpose is to ensure that designers and contractors have the information they need to plan their work safely, to identify and manage risks from the outset, and to avoid situations where dangerous discoveries are made mid-construction without preparation.

For London residential projects, pre-construction information is particularly important because London's dense urban environment, aged building stock, and complex below-ground infrastructure mean that the number of potential health and safety hazards that need to be anticipated before work begins is unusually high.

The duty to ensure PCI is assembled rests with the client (homeowner) — but in practice, this duty is almost always discharged by appointing a Principal Designer (PD) who takes on the responsibility for coordinating pre-construction health and safety under CDM 2015.

The Principal Designer is a designer (architect, structural engineer, or other design professional) with the skills, knowledge, and experience to manage health and safety during the pre-construction phase. They gather and compile the relevant pre-construction information and ensure that designers and contractors receive the information relevant to their scope of work.

Note: on smaller domestic projects where only one contractor will be working and there is no domestic client appointment duty, the CDM obligation is simplified — but the practical need for comprehensive pre-construction information does not go away. A contractor who has not been given adequate PCI is pricing and planning on incomplete information, which increases risk and cost.

A thorough PCI pack for a London residential project typically includes:

Site and structure information:

• Title deeds and property information confirming boundaries and easements
• Existing building drawings where available (or a survey where not)
• Any previous structural reports, surveys, or investigations
• Historic use of the site and any known contamination

Existing services:

• Utility plans showing the routes of gas, electricity, water, drainage, and telecommunications (obtained from utility providers or from OS records)
• Location of any service routes on the site (not just in the street)
• Confirmation of drainage responsibility (sewer build-over issues, Section 104 sewers, etc.)

Structural and geotechnical:

• Any ground investigation or geotechnical reports
• Confirmation of foundation type where known
• Any records of previous subsidence, underpinning, or structural movement
• Information about party walls and shared structures

Hazardous materials:

• Asbestos survey (required for all properties likely to contain asbestos-containing materials, broadly any property built before 2000)
• Any known presence of lead paint, PCBs, or other hazardous materials in the existing structure

Party wall and neighbouring property:

• Party wall notice records
• Schedules of condition from earlier works
• Known neighbouring building situations (basements, underpinning, etc.)

Programme and access:

• Site access constraints (narrow roads, parking restrictions, restricted hours under planning or party wall conditions)
• Any access easements or rights of way

For contractors pricing a London project, the quality of the pre-construction information directly affects the quality of the estimate:

A contractor pricing without adequate PCI must either include a significant contingency for unknowns (which inflates the price) or price on optimistic assumptions (which leads to variation claims later). Neither outcome is good for the client.

A contractor pricing with good PCI can commit more accurately to a price, plan the programme more tightly, and identify risks upfront rather than in the middle of the build. Asbestos surveys in particular are essential before any demolition or strip-out work — the presence of asbestos-containing materials can require licensed contractor involvement, which materially affects programme, cost, and method.

In London specifically, the most common PCI gaps that cause problems mid-build are:

• Absence of an asbestos survey — discovered during strip-out, leading to licensed contractor mobilisation delays and cost
• Unknown drainage routes — build-over approval requirements discovered mid-excavation
• Unknown services — gas or electricity services in unexpectedly close proximity to the works
• Unknown foundation depth — particularly relevant to extensions where the new foundation must be deeper than existing

rcbGroup reviews the available pre-construction information for every London project as part of our pre-construction programme. Where we identify gaps in the information that present material risk, we advise the client to commission the relevant survey or investigation before we finalise pricing.

We do not price around unknown risks and then claim for them mid-build. Our preference is for clients to understand what is — and is not — known before pricing is finalised. This is part of our design-and-build approach to pre-construction clarity.

If you have an existing pack of drawings, surveys, or reports for your project, our team will review them and tell you what, if anything, is missing for reliable pricing.

Contact rcbGroup to discuss the pre-construction information requirements for your London project.