Understanding CDM 2015 — A Plain English Guide

CDM 2015 · Plain English Guide

Understanding
CDM 2015

A clear, jargon-free guide to the Construction Design & Management Regulations 2015 — what they mean, who is responsible for what, and how they protect everyone involved in your project.

📖 Written in plain English — no prior knowledge needed. Whether you are a client, a developer, or simply want to understand what CDM means for your project, this guide is for you.

📋 What’s in this guide

1 What is pre-construction planning?
2 The two phases explained
3 Risk management through design
4 Pre-construction information
5 The construction phase plan
6 The health & safety file
7 Design risk assessment
8 Quick summary

Part 1 of 3

Planning, Managing & Monitoring — Before & During the Build

This is about making sure health and safety is properly thought about and organised — from the very first drawing on paper right through to when the last worker leaves site.

Think of it this way

Imagine organising a large catered event. You don’t simply hope on the night that the food arrives, the chef knows the menu, and no one has allergies. You plan it in advance, check everything is in order, and keep a close eye on things throughout. CDM works exactly the same way — but for construction projects.

🤔 Why does planning matter so much?

Most accidents on construction sites happen not because workers are careless, but because hazards were not identified early enough. If safety is only considered once work has started, it becomes far harder — and far more expensive — to address. CDM exists to ensure that everyone involved thinks about safety from the very beginning, during the design stage, before anyone picks up a tool.

Research shows that around 60% of construction fatalities could have been prevented if health and safety had been properly considered during the design and planning stage. That is a compelling reason to take this seriously.

📅 The Two Phases — what are they?

Every construction project passes through two distinct phases, each requiring careful health and safety management:

📐

Phase 1 — Pre-Construction (Before Building Starts)

Everything that happens before a single brick is laid — the design stage, planning, appointments, surveys. This phase is led by the Principal Designer.

Identify hazards that could arise during the build and design them out
Co-ordinate the work of all designers so their designs do not create conflicts or hidden risks
Gather and share pre-construction information with everyone who needs it
Begin compiling the Health & Safety File
Ensure the project is ready — and safe — to proceed to construction

🦺

Phase 2 — Construction Phase (The Build Itself)

When the physical work happens on site. This phase is led by the Principal Contractor.

Manage day-to-day health and safety on site
Implement and maintain the Construction Phase Plan
Ensure all contractors work safely and in a co-ordinated way
Ensure site inductions take place and welfare facilities are provided
Consult workers on health and safety matters throughout

Key point to remember

The Principal Designer’s responsibilities are largely focused before building starts. The Principal Contractor takes over once construction begins. However, the two roles overlap — they must liaise and share information with each other throughout the whole project.

Part 1 continued

Risk Management Through Design

One of the most important ideas in CDM — and one that is entirely logical once you see it.

A simple everyday example

Imagine designing a new office building with a flat roof section requiring regular cleaning. Workers would need to go up there with ladders and scaffolding every few months — that is a risk. Or, you could design the roof differently so it never needs cleaning. The risk is gone entirely, before the building even exists. That is risk management through design.

🎯 The goal: eliminate risks before they exist

When a designer makes a decision — the shape of a structure, the materials used, how something is accessed — they are directly affecting how safe or dangerous the construction process and the finished building will be. CDM requires designers to think actively about this at every stage of the design process.

The key question every designer must ask themselves is: “Could this design decision create a risk for the people building it, maintaining it, or using it?”

🪜 The hierarchy of risk control

When a risk is identified, designers should work through this order — always trying the top option first:

▲ BEST OPTION — Always try this first

🚫

1. Eliminate the risk entirely

Change the design so the hazard does not exist at all. Example: design a building so roof access for maintenance is never required.

🔽

2. Reduce the risk

If elimination is not possible, make the risk smaller or less likely. Example: choose materials that require minimal maintenance at height.

🛡️

3. Control the risk

Put measures in place to manage the remaining risk. Example: design permanent anchor points on the roof so maintenance workers can clip on safely.

⚠️

4. Inform others about residual risk

If risk remains, communicate it clearly to contractors and future users. This information goes into the Health & Safety File.

▼ Only rely on this if the above options are exhausted

Part 2 of 3

The Three Key Documents

CDM 2015 requires three specific documents to be produced on most projects. Each serves a different purpose and is used at a different stage of the project.

Think of it this way

Think of the three documents like a medical record. The pre-construction information is what the patient tells the doctor before an operation — existing conditions, allergies, history. The construction phase plan is the surgeon’s plan for the operation itself. The health & safety file is the post-op notes kept for future doctors to refer to.

📋

Document 1: Pre-Construction Information

Gathered before work begins · Responsibility of the Client & Principal Designer

This is a collection of all the important information about the site and the project that could affect health and safety — gathered before any construction work starts. Think of it as a “what we know about this site” document.

Why does it matter? Imagine a contractor arriving on site unaware of an old underground fuel tank beneath where they are digging, or that asbestos was found in a previous survey. Pre-construction information prevents these dangerous surprises.

What kind of information goes in it?

Things like: the presence of asbestos, underground services (gas pipes, electricity cables), ground conditions, structural drawings, environmental constraints, results of surveys, information about the existing building if it is a refurbishment, and any previous Health & Safety Files from earlier projects on the site.

Who collects it?

The client is responsible for gathering what they already hold. The Principal Designer helps pull it all together and ensures it is shared with designers and contractors who need it.

When is it shared?

It must be provided to any designer or contractor before they start work, so they can properly plan their work with safety in mind. Contractors also need it in order to prepare the Construction Phase Plan.

Example

A client wants to refurbish an old factory. Before appointing contractors, the client — with the Principal Designer’s help — gathers the original building drawings, an asbestos survey, details of underground drainage, and records of any previous contamination on the site. All of this goes into the pre-construction information pack and is provided to every contractor before work begins.

📄

Document 2: Construction Phase Plan

Written before work starts · Responsibility of the Principal Contractor (or contractor)

This is the working health and safety document for the construction site. It sets out how health and safety will be managed during the build. Every project — no matter how small — must have one.

Important: it is a live document. It is not written once and filed away — it should be updated and refined as the project progresses and circumstances change.

What does it contain?

A description of the project, the management structure, how risks will be managed, arrangements for site induction, welfare facilities, first aid, emergency procedures, how contractors will co-ordinate with each other, and arrangements for consulting workers.

Who writes it?

On projects with more than one contractor, the Principal Contractor writes it. On single-contractor projects, the contractor themselves writes it. The Principal Designer must confirm it is suitable before construction work starts.

What is the difference between this and a risk assessment?

A risk assessment looks at specific tasks or hazards. The Construction Phase Plan is the broader picture — the overall management framework for health and safety across the whole project. It will reference and include individual risk assessments and method statements.

Key point

The Principal Designer must be satisfied that the Construction Phase Plan is in place and suitable before the construction phase begins. The Principal Designer does not write it — that is the Principal Contractor’s responsibility — but must confirm it is adequate before work starts.

📁

Document 3: The Health & Safety File

Built up throughout · Handed over at the end · Responsibility of the Principal Designer

The Health & Safety File is a record of important health and safety information about the finished building. It is not about what happened during the build — it is about what future owners, maintenance workers, or demolition contractors will need to know to work safely on or in the building.

Think of it as the building’s “owner’s manual” — but for health and safety.

What goes in it?

Information about the structure (as-built drawings), materials used (including anything hazardous such as asbestos or lead paint), the location of services (electricity, gas, water), how to safely access and maintain the building, and any residual risks that future workers need to be aware of.

Who creates it?

The Principal Designer is responsible for starting and building it up during the project. At completion, it is handed to the client, who must then keep it safe and make it available to anyone who needs to work on the building in the future.

What happens to it after handover?

The client must keep it and make it available to anyone planning future construction, maintenance or refurbishment work on the building. If the building is sold, the file must be passed on to the new owner.

Why it matters — a real scenario

Ten years after a building is completed, a new owner wants to knock through a wall. Without a Health & Safety File, they have no way of knowing whether that wall contains hidden services, structural steelwork, or hazardous materials. With the file, they can check before anyone starts cutting. It could literally save a life.

Part 3 of 3

Design Risk Assessment

This is a topic that often sounds more complex than it is. Here is a straightforward explanation.

Think of it this way

When a chef plans a new dish, they think: “Could someone be allergic to this ingredient? Could the cooking method cause a problem? Can we substitute something safer?” A Design Risk Assessment works the same way — but for buildings. The designer thinks through their design decisions and asks “what could go wrong, and can I design it out?”

📝 What is a Design Risk Assessment?

A Design Risk Assessment (DRA) is a record of the significant risks a designer has identified in their design, what they have done to eliminate or reduce those risks, and any residual risks that remain which need to be communicated to contractors or included in the Health & Safety File.

It is not a list of every conceivable risk. It focuses on significant, reasonably foreseeable risks — those that could cause serious harm.

The designer’s key questions

✦ Could this design create a risk during construction? (e.g. working at height, confined spaces, heavy lifts)

✦ Could this design create a risk once the building is in use? (e.g. windows that are difficult to clean safely)

✦ Could this design create a risk during future maintenance or refurbishment? (e.g. services that cannot be easily isolated)

✦ Could this design create a risk during eventual demolition?

✦ Can the design be changed to eliminate or reduce this risk?

✦ If the risk cannot be eliminated, what information needs to be passed on to others?

🤝 The Principal Designer’s role in design risk

While individual designers prepare their own DRAs, the Principal Designer has a co-ordinating role across the whole project. They ensure that designers have genuinely considered the risks in their designs; that risks across different designers’ work do not clash or compound each other; that residual risks are properly documented; and that the overall picture of risk is managed coherently throughout the design process.

Worked example

A designer is working on a new school and specifies a glass atrium roof. They consider: “This roof will need cleaning. Someone will need to go up there — that is a working at height risk. Can it be eliminated?”

They specify self-cleaning glass — the working at height risk for cleaning is eliminated. However, the glass still needs occasional inspection. They cannot eliminate that risk entirely, so instead they design in permanent anchor points and record this in the Health & Safety File so future maintenance workers know the anchor points are available and where they are.

That is exactly how design risk management is supposed to work.

Quick Summary

The Key Things to Remember

A concise summary of the most important points covered in this guide:

CDM 2015 at a glance

✦

Pre-construction phase = the design and planning stage. The Principal Designer leads health and safety here.

✦

Construction phase = the actual build. The Principal Contractor leads health and safety here.

✦

Pre-construction information = everything known about the site — shared with everyone before work starts.

✦

Construction Phase Plan = how safety will be managed during the build — written by the Principal Contractor, confirmed adequate by the Principal Designer.

✦

Health & Safety File = what future workers need to know about the building — compiled by the Principal Designer, handed to the client at completion.

✦

Design Risk Assessment = designers thinking ahead — can this hazard be designed out before it becomes a real-world problem?

✦

The golden rule = the earlier safety is considered, the easier and cheaper it is to address. Problems solved on paper cost almost nothing. Problems solved on site can cost lives.

How We Can Help

As an appointed Principal Designer, we work with clients, designers and contractors to ensure CDM 2015 obligations are met at every stage of your project — from the first design decision to the handover of the Health & Safety File. If you would like to discuss your project and how we can support you, we would be happy to help.

Get in Touch