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 The MCHW Update Explained: What the 2025 Changes Mean for Highway Materials

 

In September 2025, a comprehensive update was made to the Manual of Contract Documents for Highway Works (MCHW). While the changes are significant on paper, the practical impact for contractors, specifiers, and material suppliers is more nuanced. This article explains what has changed, what has stayed the same, and what you need to be aware of when specifying or supplying aggregates in 2026 and beyond.

 

First Things First: Existing Contracts

One important point to clarify at the outset is that there is no requirement to retrospectively update existing contract documents. Many major schemes starting this year will still be operating under older versions of the MCHW and Specification for Highway Works (SHW), because their documentation was written before the September 2025 update. Both versions will therefore coexist for some time, and understanding which specification applies to your project remains critical.

 

Why was the MCHW Updated?

The update was driven by several long‑standing issues with the previous structure of the MCHW, including:

  • Documents that had become out of date
  • A structure that was difficult to navigate
  • Inconsistencies in style and formatting across volumes

Previously, the MCHW consisted of seven volumes, with related information often spread across multiple documents. The update condenses this into three volumes, consolidating material and activity‑related content into a clearer, more logical structure. Information relevant to construction products and materials now sits primarily within the Specification for Highway Works (SHW), which is the key reference point for both constructors and material producers.

 

A New Document Naming Structure

One of the most noticeable changes is the withdrawal of familiar SHW Series documents, such as Series 500, 600, and 800. These have been replaced with a new “CC” document naming system. The most relevant changes for aggregates and earthworks are:

  • Series 500 – Drainage and Service Ducts becomes CC 500 – Drainage
  • Series 600 – Earthworks becomes CC 601 – Earthworks
  • Series 800 – Road Pavements – Unbound, Cement and Hydraulically Bound – becomes CC 201 – Pavement Foundation Construction

While CC 500 and CC 601 broadly mirror the scope of their previous equivalents, CC 201 represents a substantial shift in how pavement foundations are specified.

 

What’s Different about CC 201?

Under the old structure, Series 800 focused primarily on sub‑base materials. CC 201 goes much further, covering all aspects of pavement foundation construction. This includes:

  • Sub‑base materials
  • Capping materials (6F1 to 6F5), previously covered in Series 600
  • Options for asphalt and concrete sub‑bases, incorporating elements previously found in Series 700, 900, and 1000

 

One Requirement per Clause

Another important structural change is the move to one requirement per clause. Older SHW documents often bundled multiple requirements into a single clause, which could lead to ambiguity. The new CC documents are deliberately more granular, improving clarity and reducing scope for misinterpretation.

A practical example of this is Type 1 sub‑base. Under the old SHW, Type 1 was defined in Clause 803. That clause no longer exists. Instead, Type 1 requirements are now set out across CC 201 Clauses 8.23 to 8.27, with each clause addressing a single, specific requirement. Many people will continue to refer to “Clause 803” out of habit, formally, those references have now been superseded but we expect to be hearing “Clause 803” used for the foreseeable future.

 

So, What has Stayed the Same?

Despite the structural overhaul, the reassuring news is that the materials themselves, and their core performance requirements, have largely not changed. A Type 1 material is still a Type 1 material, and it is expected to perform in the same way it always has.

What has changed is how those requirements are referenced, located, and applied within contract documentation. For customers, this means that material compliance is still familiar, but paperwork, specifications, and technical queries may look different.

 

Works Specific Requirements (WSRs)

As before, deviations from standard SHW requirements can still be made on a contract‑specific basis. These are now formalised through Works Specific Requirements (WSRs). Templates and guidance for WSRs are provided within the relevant “Instructions for Specifiers” documents, such as CP 201 for CC 201.

For suppliers and contractors alike, this reinforces the importance of checking not just the core specification, but also any project‑specific amendments that may apply.

 

What this Means for Day Aggregates Customers

For most projects, the biggest impact of the 2025 MCHW update is administrative rather than material‑based. Customers may see new document references, clause numbers, and terminology, but the aggregates being supplied remain fundamentally the same.