Glulam Building: Start to Finish – Part Seven C

 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 7C: Face Bonding

Glue spreader

With full length plies prepared, it is now time to create the glulam beam depth. Each ply is first run through a planer to even the wide surface of each board and prepare it for gluing. Phenol resorcinol glue is mixed with a catalyst to activate and is then loaded into our glue spreader. Plies run through the glue spreader one at a time to coat both sides (one side only for the first and last ply) with glue, and placed on the form. Steel clamps are assembled to both align and clamp the plies together, providing bonding pressure and squeezing excess glue out of the glue lines. This assembly process needs to be competed during the working time of the glue, then we leave them clamped overnight to cure. 

Curved beams with glue squeezed out

For curved glulam members, we will first move and set our forms to the appropriate shape. Plies need to be aligned properly to cover the finished shape, but otherwise the process is similar to  straight glulam beams. No additional heat or moisture is used for curving. Simply the difference between bending individual plies (which are relatively flexible) and bending a solid glulam beam (which has much greater rigidity depending on the number of plies), means we can bend a number of plies to the form, but once bonded together they cannot straighten themselves back out. They stay close to the curved shape of the form.

The video below (youtube.com/watch) shows how we clamp pairs of curved beams.

QC Corner: For glue lines our quality control includes a number of items:

• Calibration of clamping pressure
• Destructive shear tests from end cuts of production beams to test the shear strength and glue versus wood failure of glue bond
• Cyclic delamination testing to verify the long term durability of glue lines