What is Cross Laminated Timber?

Cross laminated timber or CLT is a structural, prefabricated panel used to form environmentally sustainable, walls, roofs and floors across a wide range of structures. The gluing of both longitudinal and transverse layers, which reduces the movement of the wood, means that CLT more than meets the standards required by modern building materials.

B&K Structures offers both pure CLT systems and the possibility to incorporate CLT into a hybrid structure ensuring the best possible sustainable structural solution for each individual project.
 

How is Cross Laminated Timber made?

CLT is produced by stacking layers of timber, known as lamellas, at 90° to the layer below and gluing the lamellas together to create structural timber panels of up to 22m in length and 3.5m in width. Generally members are manufactured 2.4m in width for floor panels or up to 2.95m in width for wall panels, the length of the panels are dependent on site access and logistics.

Manufacture takes place in a factory controlled environment, using state-of-the-art CNC (Computer Numerically Controlled) joinery machines, ensuring exceptional levels of accuracy are always guaranteed. The controlled conditions under which CLT is made dramatically reduces the appearance of defects which improves construction and project delivery time, reduces costs and maximises efficiency on all levels. CLT panels can also be designed to allow for the onsite installation of bespoke windows, doors and other architectural features.

 

What is Cross Laminated Timber used for?

CLT has a wide range of applications and can be used as part of a hybrid structure or as a sole building material. Its use is well documented in almost every sector and there are numerous examples of CLT in everything from high rise buildings and large commercial office space to single storey dwellings. 

Cross Laminated Timber is primarily used for walls, roofs and floors. Because of its variance in thickness, it is highly versatile and doesn’t sacrifice integrity in place of sustainability. Its reduced weight, when compared to traditional materials like concrete, gives it considerable advantages in terms of total building weight and allows for additional storeys on a foundation of the same size.

See how CLT is used in our projects

Building with CLT: Why use Cross Laminated Timber?

CLT is an excellent alternative to traditional building materials and offers a number of unique benefits when used as in projects. Offsite construction means that CLT panels arrive ready for construction and can be erected considerably quicker than a less sustainable alternative. B&K Structures further reduce intrusion by using our Business Information Modelling (BIM) capability to allow for pre-drilled holes for follow on trades like electricians and plumbers.

Cross laminated timber panels are prefabricated and delivered to site as large structural elements meaning crane loads and erection programmed are dramatically reduced. The panels are installed, without the need for wet trades, with the aid of a crane and lightweight power tools. Site storage is reduced by just-in-time delivery scheduling and health and safety issues are minimised due to the lightweight nature of the product and the speed of erection.

Sustainability is a considerable argument for CLT’s usage. B&K’s CLT is sourced from PEFC or FSC certified and managed forests, meaning that all trees used are replaced and are only felled when they have reached peak maturity. The carbon that is stored by the trees is subsequently built into the project, removing the CO2 from the environment permanently.

Being sustainable doesn’t have to come at the cost of the building itself. Cross Laminated Timber is a robust and widely useable building material with excellent soundproofing, airtightness and fire safety properties. CLT’s manufacturing process means the working profile of the wood is minimal, allowing it to be used in cantilevered structures. Noise reduction is managed by altering the thickness of the CLT panels with many of B&K’s CLT structures exceeding UK soundproofing regulations. Fire safety is a key concern for many clients for obvious reasons. Products can be produced to resist fire for 30, 60 or 90 minutes: whilst outer layers burn, they form a layer of char which continues to provide heat resistance to the internal layers. Unlike steel, CLT maintains its structural integrity when exposed to high levels of heat because of this. Timber engineering has come a considerable way and fire safety has been built into the development of these products from the very start.

How much is Cross Laminated Timber?

Because of the bespoke nature of CLT panels and the difference in every project, this is a challenging question to answer. Speaking generally, CLT costs about the same as concrete. However, cost savings are made up in areas like logistics where the offsite construction methods mean that considerably fewer deliveries are needed. Furthermore, the reduced weight of CLT results in lower groundwork costs or additional storeys can be placed atop the current structure, allowing for a better return on investment.

CLT vs. Concrete: A Sustainability Comparison

The following infographic focuses on the comparison between Dalston Lane, a residential CLT structure built by B&K Structures, and a hypothetically similar build made from concrete. Dalston Lane is a high rise residential complex in Hackney, London, consisting of 121 homes and is 33.8m or 10 storeys at its highest point.

Volume Timber Used: 4,649m3
Number of Trees: 2,325
Area of Forest: 9,200m2
Sequestered Carbon: 3,576 Tonnes
CLT: 111 Lorry Loads
Concrete: 700 Lorry Loads
CLT: 111 Lorry Loads Concrete: 700 Lorry Loads
The reduced weight of the structure allowed 35% more apartments to be built than a concrete structure on the same foundations would have allowed for. This equates to a whole 3 storeys less.