Learning the right words and phrases is the key to understanding a new culture. So, here with “Off-site manufacture: Lesson one” is Mtech Group


Advanced panel timber frame

This generic term covers the latest developments in conventional panelised timber frame. Advanced panel timber frame is a factory-manufactured timber-stud-constructed frame with sheathing in the conventional timber-frame manner. Manufacturers are now beginning to fit rigid insulation between the studs and pre-finished windows and external doors in the panel prior to despatch to site.

Air handling units (pre-wired) (AHU)

Fully tested, pre-wired packaged units complete with integral refrigeration components and controls.


Building modules

Self-contained volumetric elements of building, typically room-sized, that have their own superstructure and are manufactured off site.

Building system

Any pre-engineered method of building that has a pre-defined scope and configuration limits. Covers all modern methods of construction.


Chiller beam assembly

A complete cooling, heating and ventilation system in one monoblock unit. It is most commonly used for offices.

Closed-panel timber frame

Differs from more traditional open-panel systems in that panels are delivered complete with insulation, services containment, vapour control layer and internal wall lining. In some cases, pre-finished and glazed windows and doors are installed.

Composite construction

Composite floor slabs comprise in-situ concrete and profiled metal decking, which acts as structural reinforcement. The slabs are supported on hot-rolled steel beams.

Concrete tunnelform

A Dutch-based in-situ concrete building system that relies on a modular volumetric mould to construct a room-sized cellular building form. In-situ concrete is poured into two half-tunnel forms, that together make the walls and ceiling of a room.

Condensing units (pre-assembled)

Part of a refrigerating mechanism that pumps vaporized refrigerant from an evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control.


Dressed products (pre-assembled)

A generic term applying to factory pre-assembled products that would otherwise be assembled on site. A typical example is a hand basin fitted with taps and waste.


Factory engineered concrete

Applies to precast concrete elements of a structure. This includes wall and floor elements, ceilings, staircases, columns and beams. FEC elements can also include building service containment routes, window and door openings and possibly thermal insulation.

Flat pack

Prefabricated elements or systems that are transported to site as 2D elements, rather than in 3D volumetric form.

Floor cassette

A factory-manufactured panel comprising a series of floor joists joined together with trimmers or end-joists to form a loadbearing element of floor construction.

Foundation (fast-track)

Precast concrete mini-piles and precast ring-beam systems for rapid installation of foundations for housing. Newer techniques include steel mini-piles and helical screw piles.


Heating pod

A “mini-plant room”, typically fully commissioned and “ready to go”, with modular boiler plant.

Hybrid building systems

Superstructure build methods that involve both panelised methods and volumetric techniques. The volumetric element has its own superstructure, and simply links with the panelised elements.


Light and air diffusers (pre-assembled)

Multi-service luminaire assemblies incorporating lighting, smoke detectors, sprinkler heads, PIR detectors, loud speakers, acoustic dampers etc.

Light-gauge-steel framing (LGSF)/Light-steel framing (LSF)

Galvanised cold-formed steel sections forming the primary structure of housing and low- to medium-rise buildings.


Modern methods of construction (MMC)

Term recently adopted by the Housing Corporation and the ODPM as a collective description for both off-site-based construction technologies and innovative on-site technologies. The latter includes thin-joint blockwork. The term is normally applied to UK housing.

Modular construction

While this effectively applies to any form of building using repeated elements of construction, modular construction commonly refers to volumetric building modules. The term can also apply to room modules, which do not incorporate their own superstructure.

Modular (electrical) wiring

A prefabricated electrical cabling system, using pre-terminated electrical cables usually made up into looms or wiring harnesses to provide the electrical distribution system for all mains small power, lighting and appliances.


Off-site construction (OSC)

This term is used interchangeably with off-site manufacturing (OSM), off-site fabrication (OSF) and off-site production (OSP). In all cases they refer to that part of the construction process carried out away from the building site, generally in a remote specialist factory. It may also refer to specially created temporary production facilities close to site – sometimes called “field factories”.

Open (cell) panel timber frame

Structural timber panels forming the inner loadbearing leaf of the cavity wall which are manufactured in factory conditions and brought to site and fixed together to form a rigid loadbearing superstructure. Open cell timber frame is the traditional form of timber frame in the UK.


Panel building systems

These comprise walls, floors and roofs in the form of flat pre-engineered panels that are erected on site to form the box-like elements of the structure that then require various levels of finishing. This term applies to all different material types.

Plant room modules (pre-assembled)

Packaged or skid-mounted pre-assembled plant rooms pre-finished in the factory, ready for direct connection to mains services on site.


Prefabricated volumetric bathrooms or kitchens, factory-finished internally, complete with mechanical and electrical services. Pods are available in timber frame, light-steel frame, hot-rolled steel frame, concrete or GRP superstructure. Larger-scale washroom pods are available for commercial buildings.


The process of designing and manufacturing building elements or sub-assemblies in the factory that are accurately dimensioned so that installation on site requires a minimum of preparation and adjustment. The term is also used to distinguish between bespoke, prototype building (traditional) and factory manufacture, which by its very nature requires pre-design and proving prior to being incorporated into the works on site.


Steel-frame building systems

Stick-build systems (see below) that use steel as the primary structural material. It is common to hear the term light-steel frame, which in this context refers to thin-gauge steel sections supplied as components or panelised elements.

Stick-build systems

Pre-engineered components (generally studs) in steel, timber and sometimes concrete that are typically bolted or fixed together on site to form a skeletal structure that is then enclosed and finished on site. In a new development called the “field factory”, roll-forming machines on site convert coiled steel strip or timber into stick elements of the required length and section.

Structurally insulated panels (SIPS)

This form of construction is used in panel building systems. Structural sandwich panels typically comprise a core of foam with plywood, oriented strand board (OSB) or cement-bonded particleboard skins, bonded together to form a one-piece structural loadbearing panel.


Timber frame

In the UK the structure of timber frame load-bearing walls is usually prefabricated as wall panels. These consist of timber studs and beams, stiffened on one side with wood-based panels, such as oriented strand board, or plasterboard. The lining of the second side of the building component, and the application of insulation and other features, usually happens on site.


Volumetric modular construction

Three-dimensional building modules that have their own superstructure and usually form the building envelope.

Still confused? Further help is at hand from Promoting Off-Site Production Applications (PROSPA), a joint venture between research body Co-Construct and Loughborough University. PROSPA is striving to categorise all of the various elements that can be embraced under the OSM umbrella.

For further information, log on to www.prospa.org

Offsite supplement Oct 2004