The new Kaikoura District Council building is a great example of Laminated Veneer Lumber (LVL) being combined with other engineered wood products including CLT in a Pres-Lam (Prestressed Laminated) timber building.
“Pres-Lam is the result of years of research and a unique collaboration between commercial and academic partners at the University of Canterbury’s School of Engineering to create innovative structural timber solutions, under the leadership of Professor Andy Buchanan. The result is a flexible, durable, eco-conscious long span or multi-storey building system that moves predictably in an earthquake but sustains no permanent damage,” says Jeff Parker, technical manager of the Wood Processors and Manufacturers Association.
The Pres-Lam prefabricated technology, owned by PTL Structural Timber Consultants, utilises engineered wood beams with cleverly embedded steel post-tensioned tendons that lock the system together. The range includes a revolutionary timber frame, wall and floor systems and quick-connect portal frames, with the flexibility to create open spaces and building layouts without the need for closely spaced columns or walls.
Jeff says Nelson Pine LVL was the predominant structural material used for Kaikoura District Council’s three-storey ‘craypot’ building.
The structure has a unique combination of LVL components glued into the CLT used in the 15 rocking shear walls, which are tied to the foundations with high strength steel bars.
He says it is the first time in the world an LVL and CLT combination has been used to make shear walls.
“The LVL is significantly stronger and was added to areas where there was maximum strain such as the each end of the walls and within the core of the walls where the largest post-tensioning strain was.”
A Potius stressed skin panel flooring system, fabricated using LVL, was also used. “The floor acts as a diaphragm between the shear walls, and unlike most commercial buildings, there is no concrete in the flooring systems. Potius roofing panels were made from a similar system and pre-insulated with polyurethane spray foam. The internal finish, which provides the ceiling lining, is a pre-primed MDF surface.”
Along with the numerous construction and sustainability benefits, one of the biggest advantages of this project for the Kaikoura District Council was the cost-to-build, which was significantly less per square metre than some other conventional builds, says Jeff.
“The result was a cost effective, time efficient, system that opens new doors in design and construction of commercial and industrial buildings.”
Professor Andy Buchanan, now retired from the University of Canterbury, is a consulting engineer with PTL Structural Timber Consultants. Andy says that the dozen or so Pres-Lam buildings in New Zealand include the Young Hunter and Trimble buildings in Christchurch, and the Massey University College of Creative Arts building in Wellington, as well as others in Nelson and Carterton.
“PTL is working on the design of many exciting new timber buildings in New Zealand, Australia and the USA, in collaboration with the suppliers of engineered timber such as LVL and CLT. Many of the taller buildings include Pres-Lam technology for rapid construction and resistance to wind and earthquakes.”
He says timber buildings are also high performers from a health and safety perspective.
“The building sites are quiet and not dusty. It is also easier to attached handrails and safety equipment to a timber structure rather than a steel or concrete building, which is an added bonus.”