Cross-laminated (Crosslam or CLT) timber - Introduction
A cross-laminated timber panel (aka 'Crosslam' or 'Xlam') is a method of construction that uses timber to form load-bearing solid timber wall, floor and roof panels. Structural openings, such as doors and windows, are incorporated within the panels. In many cases only insulation and cladding is added to the external face to achieve high standards of thermal performance.
The methodology of layering, stacking and fastening softwood boards to create panels is what differentiates the members of the SWP family. The more common cross-laminated panels are characterised by placing and gluing boards across each other in layers; Another, visually distinctive, technique is to assemble a solid panel through gluing or dowelling together a series of timber ‘posts’.
Panels are commonly fabricated up to around 4m in width and 15m in height, according to technique and manufacturer. The panels can be assembled to create most types of building including housing, which at Murray Grove in London reaches a record nine storeys.
The traditional key advantages of prefabricated components are speed, efficiency and precise tolerances. SWPs tick-off these features and combine them with attractive environmental and energy-efficient attributes such as use of a renewable resource, carbon sequestration, low waste, relatively low embodied energy and an inherent high standard of airtightness.
Some Pros & Cons of crosslam construction
Can replace structural concrete, masonry or steel
Timber is renewable and sequesters carbon during growth
Construction time is very fast - services can be installed and finishes applied whilst panel installation continues.
Higher tolerances achievable through prefabrication
Relatively light weight of panels allows reduction in the size of the foundations compared with traditional construction. Reduced concrete equates to reduced embodied energy
Avoidance of noise and dusts associated with traditional construction
Can provide thermal mass if exposed
High level of decrement delay is possible to shield from summer heat
Airtightness is easily achievable
Thermal bridging is very much reduced or eliminated entirely
Requires only limited site skills
'Dry' construction prevents moisture from being admitted into the building
Exact dimensions can be provided for custom / non-standard window and door openings
Loads such as wall cabinets can be located without the restrictions associated with other forms of construction
Prefabrication reduces the quantity of waste associated with onsite fabrication
Relatively new form of construction in the UK
Inflexibilitly- all design issues need determining ahead of fabrication. Any variations on site are very difficult and expensive to resolve.
Not usually for the inexperienced designer - however manufacturers usually provide considerable support
Inflexibility - future transformation of structure is more difficult than traditional construction