11 Modern Methods of Construction

11.3 Volumetric systems

This chapter gives guidance on meeting the Technical Requirements for volumetric systems used to form homes where the height of the top floor above ground does not exceed 18m.

Introduction

This chapter provides guidance for volumetric systems used to form homes where the height of the top floor above ground does not exceed 18m.

The guidance in this chapter does not apply to volumetric roof systems or pre-manufactured structural components made of mass engineered timber.

This chapter should be used in conjunction with Chapter 11.1 ‘MMC systems: certification, quality management, installation, and handover’. This chapter seeks to focus on areas of guidance that are unique to the system type and method of construction employed, giving references to complimentary existing guidance provided elsewhere in the Standards where relevant.

There is a strong link to all chapters in Part 6 of the Standards, particularly Chapters 6.2 and 6.10.

The term ‘Modern Methods of Construction (MMC)’ is very broad and covers a wide range of differing offsite manufactured systems and onsite construction techniques.

MMC types have been categorised and defined in the MHCLG Joint Working Group ‘MMC Definition Framework’, see Chapter 11.1 MMC systems: general requirements. The scope of the guidance in this chapter will cover volumetric systems that generally fall under Category 1 under the ‘MMC Definition Framework’ and as defined below:

Volumetric

Three-dimensional structural volumetric units fabricated offsite in a factory environment used to form all or part of the basic structure of a building. Volumetric units may incorporate varying degrees of offsite fabrication and finish, including internal and external linings, external claddings, windows and doors, internal finishes, concealed insulation, membranes, internal services, internal fixtures and fittings and fire-stopping.

Volumetric units can be used in varying configurations to form the entire structure of the home or be supported by surrounding construction. Units can be manufactured in varying structural forms and be formed from timber, concrete, steel or light gauge steel or a combination of those materials

Definitions for this chapter

Cavity	A space enclosed by elements of a building which may either be the space between the cladding system and the backing wall or the space between building elements such as volumetric units. The external wall cavity should be adequately drained, and ventilated where required.
Cavity barrier	A construction within a cavity, other than a smoke curtain, to perform either of the following functions: • close a cavity to stop smoke or flame entering • restrict the movement of smoke or flame within a cavity.
Factory installed	An element of the construction that is placed, positioned, fitted or secured in, on or as part of the unit as part of the factory construction process
Fire-stopping	A seal provided to close an imperfection of fit or design tolerance between elements or components, to restrict the spread of fire and smoke.
Installation Manual	Detailed installation guidance and information for the system compiled by the system manufacturer. The Installation Manual describes general instructions for storage and transport of the system, and procedures for on-site assembly and installation
Interface	Interface either between similar or dissimilar envelope systems (eg at panel joints) or between envelope systems and other elements of the building (eg walls, roof, doors, and windows).
Junction	The point where components, including panels are joined with each other or with other elements of the building (eg supporting structure, roofs and foundations).
Manufacturer	The company which is responsible for the design and assembly of the volumetric system.
Non-standard components	Components that are assembled as part of the system but vary for individual projects. These may be windows, doors or services that may be built into the system.
Primary structural components	Elements of the structure designed to carry and transfer primary loads of the building, including self-weight, dead loads, and live loads.
Secondary structural components	Elements of the structure which do not play a wider role in the structure, but carry loads directly imposed on them (and transfer them to the primary structure) such as self-weight, wind loads, cladding and openings.
Standard components	Components that are assembled as part of the system and are common to all projects.
System	For the purposes of this chapter, this term refers to acceptable forms of volumetric systems.
System Manual	Detailed technical information on the system compiled by the system manufacturer. The System Manual describes the system, the declared performance of the system and evidence to support the declared performance.
Unit	A prefabricated building unit, manufactured offsite as a structural or non-structural assembly in three-dimensional or flat panel format used as part of a system to form the superstructure of a building.
Volumetric	Three-dimensional structural units which are commonly stacked to form a building. Volumetric units may incorporate varying degrees of off-site fabrication and finish, including internal and external linings, external claddings, windows and doors, internal finishes, concealed insulation, membranes, internal services, internal fixtures and fittings and fire-stopping.

Clauses for 11.3 Volumetric systems

Last updated: 2nd January 2025