Plywood

The incredibly versatile material Plywood, is a wood-based man made product which comes in the form of panels. Each panel is constructed by layering thin sheets of wood, called 'plies' and adhering them together. Each ply is laid with the grain of the wood perpendicular to the layer below. This crossing of grains counteracts the warping and expanding that naturally occurs in wood, and increases the overall strength of the panel to be generally greater than that of a piece of wood of the same dimensions. Plies are typically layered in odd numbers e.g. 3, 5 or 7, so that the visible grains will run in the same direction, usually along the length of the panel. In New Zealand the standard panel sizes are 1200 x 2400mm and 1200 x 2700mm.

Plywood panels are given grades based on the aesthetic quality of the facing plies, regarding the grain and knots in the wood. The more expensive grades have a good quality of grain on both sides and are used for interior finishes and furniture where the surface remains unpainted.

The majority of plywood in New Zealand is made of Radiata pine, but companies such as Gibson Veneer and Plywood Ltd import marine grade European poplar, beech and Fijian kauri for use in boat building.
 This is an example of the very wide range of uses the characteristics of plywood lends itself to.

Through out the history of design, plywood has played an enormous role, particularly evident in the work of Charles and Ray Eames during the 1940's.

 

The legs splints and chairs designed by the Eames' were cheap, lightweight and comfortable due to their construction from plywood molded under pressure and heat, to fit the human form.

One on New Zealand's largest plywood companies Decortech, produces a large range of pre-finished plywood's, allowing custom designs, laser cutting and paint finishes to be applied to the panels which can then be installed into a space very quickly. As plywood is a wood based product, it can be easily attached using screws, which are tightly held due to the crossing grains in the plies, however the weight and use of the ply must be taken into consideration.Companies such as Decortech and Ecoply give their own recommendation of installation methods for their own products to meet industry standards. This information can be found on their websites or through direct communication with the manufacturer. Decortech also produce panels which have be coated in fire-retardant chemicals, allowing them to be used in areas which would have otherwise been unable contain a timber material due to fire safety requirements. 

Panels of plywood can be perforated with holes to be used for sound absorption in ceilings and between spaces.

Wellington Airport by Studio Pacific Architecture. Custom made perforated panels by Decortech

Though an extremely versatile material, plywood does have some limitations. The major factor to consider is water. Though less likely to warp in a dry environment than lumber, unfinished plywood will readily absorb moisture affecting the form of the wood and the integrity of the adhesive. As a material, it relies on the effectiveness of the added sealant to retain it's qualities and exterior panels in particular must be purpose built for moisture protection. 

 Groups such as the European Federation of Plywood Industry, Carter Holt Harvey and Decortech claim that through sustainable forestry practice, plywood can also be a 'carbon neutral' and renewable material, with the trees being grown for the industry absorbing the equivalent amount of CO2 produced in the production process.

Diagram of sustainable industry from The European Federation of Plywood Industry

For those interested in sourcing products made in New Zealand from local materials, plywood could be a viable option. It's no surprise then that we are seeing it used more and more in local design.

Prices for Plywood vary greatly depending on the number of plies, the grade of the wood, and it's intended application ranging from cheaper DD grade construction plywood, to the highly finished, treated and fire retardant panels. Standard Radiata pine un-treated and treated sheets can be bought from all major building supply stores.

Further information on the use of Plywood and other wood based materials in New Zealand building can be found at NZ WOOD.

By Charlotte McKirdy