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The resource centre for offsite and other non-conventional construction


Panelised relates to off-site manufacture of wall, floor and roof panels which are assembled on-site into three dimensional structures. Common types of panelised systems are outlined in more detail below.

Open panel systems

Open panel systems: are skeleton frames, typically in timber or lightweight steel and are manufactured in factory conditions. Open panels may have sheathing board installed to one side of the panel. Open panels will be transported to site where the insulation, vapour control layers, linings and claddings are fitted along with the services and components such as windows.

It is possible that cold rolled steel building systems can demonstrate compliance with NHBC Standards Chapter 6.10 Light Steel Framed Walls and Floors, via stage 1 certification issued by the Steel Construction Institute (SCI) in accordance with NHBC Standards Chapter clause 6.10.3. NHBC requires the builder to appoint an NHBC approved steel frame certifier to check the design for the home and the site.

For timber systems, reference should be made to NHBC Standards Chapter 6.2 External Timber Framed Walls, clause 6.2.3 Design and Certification where the design of the Superstructure shall be checked by an NHBC approved timber frame certifier. The registered builder should ensure that the completed HB2445 certificate is available on-site for inspection by NHBC.

Closed panel systems

Closed panel systems: are fully assembled and enclosed within the factory. Closed panels comprise the same components as open panels, however, the entire assembly and sealing of the panels is undertaken off-site.

In addition to demonstrating compliance with NHBC Standards Chapter 6.2, the manufacturer should demonstrate that the closed panels are manufactured under a quality management system, including factory production control and working to established performance requirements. The manufacturer should provide appropriate on-site quality assurance. Closed panels may be registered with the Structural Timber Association or BM TRADA.

Cross Laminated Timber (CLT)

Cross Laminated Timber (CLT) systems are off-site manufactured engineered solid panels. The panels are manufactured by laminating small lengths of timber with adjacent layers having their grain direction at right angles to one another. Panels can be used to form structural floor, wall, and roof elements; beams, columns, lift shafts, and stairs.

Reference should be made to NHBC Standards Chapter 2.1 The Standards and Technical Requirements, Technical Requirement R3 a). The BS EN 16351:2015 Timber Structures - Cross Laminated Timber requirements, sets out the provisions regarding the performance characteristics for straight and curved structural CLT, both with and without large finger joints as a material for the manufacture of structural elements to be used within buildings. The European Standard sets minimum production requirements and procedures for assessment and verification of consistency of performance.

Structural Insulated Panels (SIPs)

Structural Insulated Panels (SIPs): are off-site manufactured products that can be used to form structural floors, walls and roof elements, or infill panels to a primary structure.

SIPs systems should be assessed and certified by a technical approvals authority in accordance with NHBC Standards Chapter 2.1 The Standards and Technical Requirements, Technical Requirement R3a) iv).

Care must be taken to ensure that the Construction meets relevant Building Regulations, NHBC Standards, British Standards, Eurocodes and (or) statutory requirements on a site-by-site basis.