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Single-Storey Frames, Shells and Lightweight Coverings 195
Photograph 4.10 Glue-laminated timber frame and roof.
members and as thin as 13 mm for curved members. Laminates are kiln dried to a moisture
content of 12%. Individual lengths of timber are finger jointed at the butt end. The ends of
the laminae are cut or stamped to form interlocking protruding fingers that are 50 mm
long. The lengths of the end jointed laminates are planed to the required thickness and a
waterproof adhesive is applied to the faces to be joined. The adhesive used is, like the wood
it is used to bond, resistant to chemical attack in polluted atmospheres and chemical
solutions.
The adhesive-coated laminates are assembled in sets to suit the straight or curved section
member they will form. Before the adhesive hardens, the laminates for curved members
are pulled around steel jigs to form the shape required. Both straight and curved sets are
hydraulically cramped up until the adhesive is hardened. After assembly the glulam
members are cured in controlled conditions of temperature and humidity to the required
moisture content. The surfaces of the straight members are then planed to remove adhesive
that has been squeezed out and to reduce the section to its required dimensions and surface
finish. Curved members are made oversize. The staggered ends of laminae are then cut to
the required outside and inside curvature and the faces are then planed in the same manner
as that for the straight members. The planed natural finish of the wood is usually left
untreated to expose the natural colour and grain of the wood.
Timber decking can be used to serve as a natural wood finish to ceilings between glulam
frames and rafters and as solid deck to support the roof covering and thermal insulation.
The decking is laid across and screwed or nailed to roof beams and portal frames.
Symmetrical pitch glulam timber portal frame
These portal frames are usually fabricated in two sections for ease of transportation to the
site. They are erected and bolted together at the ridge as illustrated in Figure 4.39. The