What are the key differences between CLT and Glulam?
Both Cross-laminated timber (CLT), and glue-laminated timber (glulam) are engineered wood products that are commonly used for mass timber construction projects. One commonly asked question is what is the difference between glulam timber construction, and CLT construction?
First, to understand the differences it is important to understand what laminated timber is. This is an engineered product, meaning it is man-made and not naturally occurring like wood planks would be. Adhesives are used to bind together multiple layers of timber to create a strong, engineered product.
Differences Between CLT and Glulam
Here is where the differences lie. CLT timber has each layer combined with adhesives with the grain alternating at 90 degrees between each later. Glulam timber has each layer combined with the grain lined up. So why is this important?
There are some key differences and reasons for each of these over the other.
Because CLT is made with layers alternating at 90 degrees to each other it has strength in 2 directions and so has 2 way spanning characteristics similar to a concrete slab. The direction in which the most number of layers are oriented is the strong axis and the direction with the least is the weak axis. This 2 way spanning characteristic was notably taken advantage of at Brock Commons Tallwood House where glulam columns were located to maximize the strong axis and weak axis of the 5-ply CLT floors and so any glulam beams were eliminated.
Because glulam is made with layers all oriented in the same direction it is used most commonly for one way spanning requirements such as columns, beams and trusses. Glulam on the west coast of North America is most often made with Douglas Fir which has excellent strength characteristics but it can be made with many other species of softwood and hardwood. Interestingly beech hardwood is recently being used to make glulam for specialty projects and with incredible results. A factory we toured last December in Germany has trusses made with beech glulam and incredibly they span up to 120 meters almost 400 feet!
Most often mass timber projects use both glulam and CLT and each is used to take best advantage of their unique characteristics.
With all the benefits of engineered mass timber, this industry will continue to grow and develop. Make sure you consider it for your next building project.