Glulam Building: Start to Finish – Part Seven B

 Welcome to our “Glulam Building: Start to Finish” series. Our goal is to provide an overview – from idea to completion – of a glulam building, from the perspective of a glulam manufacturer and designer.

Part 7B: Finger Jointing

We now begin the process of making a wood structural component that you cannot cut from a tree. Beginning with standard dimensional lumber, we can create a glulam beam whose size is only limited by the ability to finish, handle, and ship it.

Working on 110′ long plies for utility pole

The first step in this process is to create the beam length, and this is done by finger jointing. Groups of boards are loaded into our scarfer. Each end of every board is cut square, routed to a finger joint  profile, and coated with a melamine resin glue. Ends are assembled, tightly pressed together, and run through a microwave tunnel to quickly cure the glue. This creates a continuous board which we cut to length, this will become a single ply in the glulam billet we are producing.

Finger joints in a Doug Fir beam

Finger jointing is a critical step in the creating of a structural glued laminated timber. Here at Unalam. we use a vertical finger joint, where the finger pattern is visible on the wide face of the laminations.

QC Corner: Our manufacturing process includes strict quality control standards and tests. We’ll begin to cover these with a “QC Corner” appropriate to each step of the process. To backtrack a bit, during the Grading Lumber step, quality control includes the certification of employees who perform visual grading, and inline testing of the wood moisture content.

For finger joints we have a series of visual and destructive tests:

• Visual inspection of finger joint cut profile
• Proof loading of all finger joints in tension laminations
  
• Full scale destructive tension tests of cured finger joints
• Cyclic delamination testing to verify long term durability of glue bond at finger joints