Sustainable Western Red Cedar from Evalock Cedar Windows & Doors

A guide to Western Red Cedar

Western Red Cedar (Thuja plicata) grows along the West Coast of North America and in Canada is only found in the province of British Columbia. Trees normally grow to heights of 45-60 metres with a diameter of 2.4m.

Western red cedar has been an integral part of the lives of Canadian First Nations people who used the wood, bark and roots of the trees in their daily lives and as early as 1535 gave the French explorer Jacques Cartier extracts to cure scurvy.

WRC's slow growth and naturally occurring fungicidal compounds called thujuplicins helps make the wood resistant to insect attack. Light in weight and with a soft texture Western red cedar is an extremely dimensionally stable wood that seasons easily and quickly with low shrinkage factor. Its heartwood has natural decay resistance.

Doors and windows are major end users of Western red cedar, utilising the wood's weather resistance, stability, longevity and excellent working properties

Freedom from pitch and resin gives Western red cedar excellent finishing properties. Its dimensional stability is an ideal base for a variety of finishes, either full-bodied paints or stains or semi transparent products. It has good gluing qualities and nailing properties. Properly finished and maintained, cedar will deliver decades of trouble free service. Leaving WRC untreated is not recommended because a finish or protective coating will greatly increase its service life.

The corrosive nature of WRC extractives requires the use of corrosion resistant nails and screws (eg stainless steel, hot dipped galvanised and high tensile strength aluminium. Used outdoors, non resistant nails such as common iron, wire and copper nails rapidly deteriorate and decompose, accelerating the oxidative deterioration of wood around the nails. In year or so holes appear where the nails used to be. WRC has low nail screw or bolt holding capacity requiring about one third longer or larger diameter fastenings than hardwood species.

The flame spread rating (measure of the rate of advance of flame along the surface of wood) and smoke developed classification (reflects the amount of smoke released by a burning material) of WRC is considerably below the maximum limits set by US and Canadian Building Codes. Australia, as yet, does not have these standards.

Chemical Staining.

Staining can be encountered on surfaces exposed to the weather. When ordinary steel nails are used, a blue black discolouration appears around the nail head. Sometimes within months of installation staining occurs as small specks of brown exudate or as patches of reddish-brown discolouration on finished exterior surfaces.

The stains may be washed away easily with water on first appearance, but become insoluble under the action of sunlight and air. The improper use of aqueous emulsion or latex paints applied directly to a cedar surface without modification could cause this to happen. Prevention is by priming the surface properly with an oil-based coat or by the addition of chemicals to the first coat of latex paint.

Transparent non-flexible film forming finishes such as lacquer, shellac, urethane and varnish are not recommended for exterior use on cedar. Ultraviolet radiation can penetrate the film and degrade the wood. Regardless of the number of coats the finish will eventually become brittle, develop cracks and fail.

The above extract is from a publication "Growth, Properties and Uses of Western Red Cedar" by Josefina S Gonzalez (Second Edition) March 2004 Forintek Canada Corp, Special Publication No. SP-37R ISSN No.0824-2119