Glossary of Terms

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Air Handling Unit (pre-wired) (AHU)

Packaged air handling unit fully tested, pre-wired packaged unit complete with integral refrigeration components and controls.

Components: Machinery

Bathroom Pod

For more information see Pod 

Systems: Pods     Components: Component Suppliers

Beam and Column Frame

For more information see Frame 

Systems: Glulam     Components: Fixings & Fastenings


The Buildoffsite  Property Assurance Scheme incorporates assurance and insurance as a means of mitigating many of the perceived risks to which the lending community and other key stakeholders in the residential market are exposed, in relation to offsite construction systems and techniques. The scheme incorporates an assessment against best practice of manufacturing and construction systems, construction system integrity and durability. It is supported by a national database of residential properties assured under the scheme, which may be readily assessed by valuers to support informed and accurate valuations.

Systems: CLT/Glulam, Glulam, Hybrid, Light Steel Frame, Pods, Precast Concrete, SIPS, Timber Frame, Volumetric Modular

Brick Slips

Commonly used on Offsite manufactured external walls to replicate the appearance of conventional brickwork. Brick slips are generally 20mm thick compared with a 100mm standard brick. The slips are fixed with glue to the metal or plastic frame of an external wall panel.

Components: Fixings & Fastenings

Building Information Modelling (BIM)

Building Information Modelling (BIM) is used to generate and manage data throughout the entire life cycle of the building, from inception, design, through to demolition and recycling. Models are created that contain not only the building geometry, but are data-rich in terms of relations, physical attributes, time, costs and quantities. The result is a collaborate tool that can be used by the whole project team, clients and end users. Benefits include a significant reduction in risk through improved co-ordination, control and flow of information, improved accuracy of cost and programme planning, increased productivity, efficiency and predictability because of managing teams and data centrally and reduced rework on site.

Components: Software Provider

Building System

Any pre-engineered method of building that has a pre-defined scoped and configuration limits. Building systems can be volumetric, panel, stick build or hybrid. 

Systems: Hybrid, Volumetric Modular

Cable Containment (preassembled)

Cable system incorporating preassembled bracketry. Brackets supplied complete with preassembled spring nuts and bolts. Systems vary and can include:

  • Both bolted and welded forms
  • Trapezes and other non-standard bracketry
  • Fixing rails, cantilever arms and various accessories
Components: Fixings & Fastenings

Chimney (prefabricated)

The factory production of chimneys (mainly for residential projects). In situ chimneys are problem areas for consistency of quality for example in terms of insulation.

Components: Insulation

Closed Panel Systems

Systems: Timber Frame     Components: Insulation

Combined and Single Service Horizontal Rack

(Also called Ceiling Void Module)  Integrated ductwork with pipe work and cable management support trays into a multi-services module mounted in the ceiling or under the floor. Usually constructed as an open frame structure, which reduces the overall weight of each section.

Horizontal distribution has been in use for many years, but more recently mechanical ducting or pipework systems/modules are usually combined with electrical service distribution. Often “supply and fit,” these systems are fully manufactured offsite in factory conditions. While the pipework or ducting can be tested in the factory the system once connected must be system-tested and commissioned onsite. Modules should be constructed to give ease of access in the long term. Examples have shown that two operatives can install over 90m of pipework and over 45m of cabling support in one day.

Components: Flooring, Roofing

Combined Pod

Follows a typical bathroom pod technique, but combines a factory-finished bathroom with a pre-serviced kitchen, airing cupboard/hot water cylinder or boiler plant with BMS etc. This is not a commonly used option but there are some examples where this approach has been considered at the design stage. See also Pods.

Systems: Pods


A term used loosely for items that are manufactured offsite and then assembled together with other components. If this is completed offsite then the product is defined on a whole. If this is carried out onsite then it falls into Category 1. Careful design of components and their interfaces is crucial for effective manufacture and assembly.

Systems: CLT/Glulam, Glulam, Hybrid, Light Steel Frame, Pods, Precast Concrete, SIPS, Timber Frame, Volumetric Modular

Composite Construction

A generic term covering a wide variety of construction techniques, particularly where two different materials are used in combination to fulfil a specific function.

For example, composite floor slabs can comprise in situ concrete with profiled metal decking, which acts as structural reinforcement. These slabs are supported on hot-rolled steel beams. Often, the beams are composite themselves, using shear connectors (normally welded headed studs) to achieve structural efficient with good spanning capability. Composite Construction can also use pre-cast concrete slabs with a composite structural screed. Composite Construction is also known as Hybrid Construction.

Systems: Hybrid, Precast Concrete     Components: Insulated Concrete Formworks


Concrete is a fundamentally important material to offsite construction. Precast and pre-stressed units and formwork include elements such as the structural frame, supporting columns, panels, beams and flat slabs. These can be used to create most building types. The concrete elements may be factory-finished internally including services, windows, doors and finishes.  Externally they can remain exposed in the final building. Precast concrete may be used with in-situ concrete or structural steel as part of a hybrid frame and can be integrated with cladding systems, volumetric and pod technology. Precast concrete systems are also used to rapidly build foundations. The concrete elements are usually to a bespoke design and cast in a factory environment, giving guaranteed quality for the finished product.

Systems: Precast Concrete     Components: Insulated Concrete Formworks

Cross Laminated Timber (CLT)

Increasingly popular as part of hybrid builds and multi-storey timber structures, CLT panels are precision-manufactured to any dimension and shape from single-layer timber boards then glued together at right angles to form large solid timber panels for walls, floors and roofing. CLT panels have huge structural potential and are suitable for most building types.  

Systems: Hybrid, Timber Frame     Components: Flooring, Roofing

Cross Wall Construction

Multi-storey structure where the walls are designed as the means of primary support. Longitudinal stability is achieved by the external wall panels and/or diaphragm action involving the floors and roof, connected back to lift cores or staircases, which may also be formed by pre-cast wall panels or shaft units.

Systems: Precast Concrete     Components: Flooring, Roofing

Design for Manufacture and Assembly (DFMA)

In the construction industry, Design for Manufacture and Assembly (DFMA) involves improving quality through the application of efficiency.

Finding the most efficient way of delivering a project reduces the resources required (whether this is measured in cost, time, carbon, waste or labour) while increasing positive aspects such as health and safety, quality, certainty. A DFMA solution can be achieved to a higher quality at lower cost and in less time.

DFMA takes many forms, but the common factor is the application of factory (or factory-like) conditions to construction projects.

A DFMA solution starts by understanding the end product and draws upon the range of suppliers and systems available. Varying degrees of "granularity" can be added according to the project requirements. Volumetric solutions create as much of the finished product as possible in the factory, with on-site labour minimised. "Flat pack" or panelised create a kit of parts that can be quickly assembled on site. Often prefabricated sub-assemblies (M&E services, for instance) are deployed in conjunction with more traditional build elements.

For some situations, traditional build elements may be used but the site is effectively turned into a factory. Pre-packed "fit out kits" are delivered to the work face with everything needed for the work. Waste is virtually eliminated, along with the most common causes of delay on site, i.e. lack of materials, follow-on trades and reworking.

DFMA also allows for buildings to be deconstructed more safely, with components or even entire buildings able to be reconfigured or redeployed elsewhere. This is the ultimate form of sustainable construction.

Systems: Volumetric Modular     Components: Software Provider

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