In April 2025, the British Standards Institution published PAS 8700, specifying standard requirements for Design for Manufacture and Assembly (DfMA) and modern methods of construction (MMC) in new-build residential properties.
Developed by the Ministry of Housing, Communities and Local Government, the PAS aims to increase and standardise the use of MMC, to improve quality, safety and performance and reduce the environmental impact of their housing projects.
The PAS 8700 recommendations
One of PAS 8700's key recommendations for clients is to appoint an "MMC adviser", with responsibility for liaising with system manufacturers to identify opportunities for the use of MMC systems. Clients are encouraged to identify existing designers in their project team who can take on this role, rather than paying for a separate consultant.
Responsibility for design should be agreed at RIBA Stage 1. PAS 8700 recommends that design development should allow for flexibility and competition in the choice of MMC system, though teams should agree a point at which design elements are finalised (a "design freeze"). This will be particularly important for Higher-Risk Building projects required to get building control approval from the Building Safety Regulator, where designs must be submitted and approved prior to construction works starting on site.
PAS 8700 also recommends appointing an MMC system structural engineer, with responsibility for agreeing codes and standards for the project design works. There should be a documented and auditable quality management system, to assure the compliant manufacture and production of systems, assemblies and components. The PAS contains useful flowcharts identifying the key handover points and construction interfaces at which quality inspections should be undertaken.
Another recommendation is for project teams to create a risk register at the start of the project (or at RIBA stage 0), assigning responsibility to parties for identified risks and agreed risk mitigation activities. Risk registers should be reviewed at each key project stage until the completion of the project, with team members being made aware of critical outstanding risks.
PAS 8700 also recommends early engagement with insurers to procure latent defects insurance cover for modular and manufactured systems. Obtaining defects liability insurance can be a lengthy process: many MMC systems have limited historical data to support performance or confirm actual loss experience, which can affect policy coverage, and most latent defects insurers will want to conduct technical assessments of the MMC system and the site. Early engagement will ensure project teams aren't left uninsured ahead of the manufacturing and installation process.
An early-stage approach under PAS 8700
The approach outlined in PAS 8700 will require clients to appoint designers and manufacturers and front-load key decisions at a much earlier stage than traditional design-and-build projects. This approach relies on clients setting out their requirements clearly, and appointing project teams with sufficient experience and knowledge of MMC and DfMA for the project. Clients are also encouraged to adopt forms of contract supporting early supplier involvement as recommended by the Construction Playbook, such as the PPC2000 contract suite or robust pre-construction agreements.
The PAS recognises that with MMC manufacturing processes, significant financial investment is required at the early stages of the project (for example, to enable materials to be obtained prior to factory production commencing). The PAS recognises the balance between funders and clients who will want to mitigate their exposure and limit or impose conditions on advance payments and deposited funds, versus manufacturers who will seek guaranteed cash flow. To mitigate the exposure presented by advanced payments, protection can be sought from escrow accounts, insurance bonds, letters of credit or advanced payment guarantees. Use of project bank accounts, as recommended by the Construction Playbook, should also be considered.
The PAS 8700 is a welcome step forward in expanding the understanding of MMC and DfMA across the housing sector, providing practical guidance for clients, contractors and designers to implement modular construction in their projects.
