Bigger timber structures now a reality

LVL columns supporting the College of Creative Arts at Massey University, Wellington Campus which is a Pres-Lam building.

New Zealand has always had the ability to build bigger timber structures. However it wasn’t until the emergence of the latest timber technologies that this has become a cost effective possibility, says Jeff Parker, technical manager of the Wood Processors and Manufacturers Association.

“The economies of using products such as CLT and LVL, combined with new construction systems and connectors being developed by the Universities of Canterbury and Auckland have seen the industry reach a tipping point which has extended timber construction into areas where it has not competed before.”

He says this is still however dependent on greater government recognition and support for the sector.

“Carbon sequestration is a big driver of change resulting in a growth in the timber sector in Australia. If the government here wants a low carbon economy similar changes seem like a no brainer. However the New Zealand government still seems pretty deaf to the wood industry overall.”

Jeff says this is frustrating when the industry is making large investments in CNC and other machinery, which has extended the utility of Glulam, LVL and CLT, making the production of ‘extremely complex’ structures significantly more cost effective.

“These technologies can rapidly saw, rout, bore and groove the timber products into components ready to be lifted, placed and fixed on site.”

Jeff says an example is a machine used by Timberlab Solutions, which enables the processing of Glulam, LVL, CLT and solid timber elements up 30m long, 4m wide and 600mm deep.

“The speed and accuracy of these manufacturing processes has significantly decreased construction time and the time required on site for heavy lifting machinery.”

Although the ‘new kid on the block’ CLT is setting the industry abuzz, LVL is now a mature engineered wood product with engineers and architects harnessing high structural and aesthetic properties, says Jeff.

“LVL can be manufactured to required strength, stiffness, shear, bearing and connector properties, with components for particular jobs manufactured to perform at optimum cost and use of resource.”

He says the very high strength to weight ratio of LVL means gravity loads are lower and therefore other structures such as foundations and connections can be smaller.

There are more new innovations entering the market when it comes to other structural products such as sawn timber, says Jeff.

“Sawn sizes of structural timber are being increasingly used in complex truss layouts, where the advanced engineering software, increased reliability of graded structural timber and ability to place LVL components in particularly high loaded areas has extended the options available to building designers.”

Classroom at Waiariki Polytechnic with LVL beams and EXPAN connections.

There are also some exciting non-structural timber products including weatherboards, decking and decorative linings being introduced to the market, says Jeff.

“One of the more spectacular’ new products is a curved 215mm timber weatherboard, which can be used to great effect to create curved exterior walls and even spiral staircase banisters.”

These weatherboards are produced by Auckland firm, Woodform, a specialist in the wood bending market for around 30 years, that has developed its own unique systems.

Jeff says several other producers have gained New Zealand Building Code approval for new conventional weatherboard systems, which have improved detailing and fixing systems.

“Some new heat treated weatherboards have also been approved for use under the Building Code, which provide an alternative to the more common timbers treated with processes infusing anti-decay chemicals.”

For products used internally there have also been developments in the ‘Reaction to Fire’ area.

The Fire clause in the Building Code previously restricted the use of clear-coated timber products in public spaces.

However the introduction of the European Single Burning item test to assign Materials Groups under the Code, has opened the door for a new, affordable range of clear coatings with Materials Group ratings of up to 1S to be available in New Zealand.

“These economic coatings stop the spread of flame but allow the timber to be left exposed, even in public areas. It is a big leap forward.”

Overseas, applied research into fire resistant systems has allowed the use of ‘light’ timber framing systems to be extended to six storey buildings.

“Work is also progressing on this front in both Australia and New Zealand. There are exciting times ahead for the industry,” says Jeff.