Cross Laminated Timber (CLT)


Cross-laminated timber CLT

  • Exceptional construction speed, with most structures watertight in days
  • Exceptional carbon storage because of the volume of timber used, making carbon negative buildings possible
  • Clean and quiet construction site with no need for heavy tools
  • Relatively low site skills
  • High comfort for occupants, with good humidity control from the ‘breathable’ structure


As of 21 December 2018, regulations were put into effect that ban combustible materials in the external wall systems of residential buildings over 18m high, stipulating that materials that form part of an external wall, or specified attachments, of a relevant building meet European Classification A2-s1, d0 or A1.


This means that timber construction systems, such as CLT, will need separation between the structure and the outer face of a residential building over six storeys high. A number of ways to achieve this can be considered, without compromising the integrity of the CLT structure. This does not affect timber frame systems, which are suitable for lower-rise buildings.


Amendments to the Building Regulations 2010, Approved Document Part B (Fire Safety) and 7 (Material and Workmanship), and further guidance can be accessed using the links below.



Cross-laminated timber panels are large, rigid, solid timber construction sheets used for all elements of a building’s superstructure – walls, floors and roofs.


They are made from kiln-dried, finger-jointed timber planks (typically spruce), cut into sheets and bonded under pressure in perpendicular layers.


CLT is an ideal material for off-site construction, with panels arriving on site machined to precise sizes, including apertures and trunking conduits.

Cross-laminated Timber are Engineered Wood Products

Timber products that have been engineered to remove natural weaknesses and enhance natural strengths. They provide stronger, longer, wider and more stable solutions than natural timber.


They deliver sustainable, low carbon structural solutions with a unique elegance, low weight and natural beauty. Engineered Wood Products include:


  • I Beams
  • Glulam
  • LVL (Laminated Veneered Lumber)
  • Engineered wood flooring
  • CLT (cross-laminated timber panels)

The Key Benefits

  • Stronger sections
  • Stiffer sections
  • Greater stability
  • Greater lengths and spans
  • Consistency – particularly as they are factory manufactured with lower moisture contents, a benefit when being installed in heated buildings




Cross-laminated timber (CLT) is a solid-wood construction panel made from at least three layers of lamella (pine or spruce) glued crosswise. The normal size is 3 x 16 metres, but panels are also available in a range of dimensions and grades. The CLT panels have pre-cut openings for doors and windows, according to customer requirements. CLT is suitable for both interior and exterior walls, as well as ceilings and flooring.


The product has attracted a great deal of interest. Major CLT-based building projects have both been completed and are ongoing all over the world with the aim of developing the market and demonstrating the competitiveness of the technique compared with concrete.  As a product, CLT has experienced double-digit growth since it was introduced in early 2000 and this trend is expected to continue in the years to come.




Sustainable timber

Timber is the most sustainable mainstream building product. It is naturally renewable. Over 90% of timber used in UK construction comes from Europe, where more trees are grown than harvested (source: TTF Statistical Review 2016).

Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores.

Ask for PEFC or FSC Chain of Custody certification.

See Wood Campus RIBA CPD module Procuring Sustainable Timber for more on timber certification and sustainability and government requirements.