Western Red Cedar - Natural Weathering


Leaving Timber to Weather Naturally

Even though timber weathers over time to an attractive silver-gray patina that has a certain architectural appeal, research chemists and wood scientists now recommend that some form of protective finish be applied to prevent surface degradation. Weathered surfaces provide a poor substrate for finishes.

 

Leaving Western Red Cedar to Weather Naturally

A lot of overseas promotional material that we see for Western Red Cedar will show it weathering naturally and used in an unfinished state. When considering this form of application, it should be borne in mind that allowing cedar to weather naturally is not suitable for all climatic conditions. What follows is intended to make the specifier fully aware of the implications of natural weathering, and draw attention to the fact that what might be done as a means of reducing maintenance could actually be creating a much higher level of maintenance.

Western Red Cedar may sometimes perform satisfactorily as a cladding product if it is left unfinished to weather naturally.

This option might be considered for a number of reasons:

  • A preference for the silvery grey look of naturally weathered Western Red Cedar.
  • A desire not to invest the time and effort required to maintain the finish on a cedar product.
  • Project inaccessibility, causing difficulty in maintaining the finish on a Western Red Cedar 
  •        project, for example, cladding on very tall buildings.
  • A concern about the environmental impact of applying a finish to Western Red Cedar.

These are all valid considerations and the reality is that Western Red Cedar cladding may have a long service life without a finish coating in some environments – as long as good design, installation and maintenance practices are followed.

 

It is important to understand that the choice not to apply a finish to external cedar products has long term implications.

This choice requires advance consideration before allowing natural weathering to begin.

As Western Red Cedar weathers, it will lose its natural color and become grey. In very dry climates, it weathers to a silvery grey color, but in most other climates, because of varying moisture and sun exposure conditions, the Western Red Cedar does not weather uniformly and is likely to develop a dark, blotchy, grey appearance. These ‘other climates’ reflect the conditions applicable in most of Australia.

Should the need arise to restore weathered cedar to a state where it can be painted or stained, significantly more effort will be required to prepare the surface of the wood for coating.

 

in some climates, Western Red Cedar does not weather uniformly

 and is likely to become dark and blotchy

 

If a truly uniform grey appearance is desired, then this effect can be achieved by the use of a commercially prepared bleaching oil or grey weathering stain. This is essentially a water repellent finish containing pigments and other additives which is most effective on textured cedar. To maintain this look, the bleaching stain may have to be re-applied periodically.

Although the natural weathering effect is usually only “skin deep” (less than 1-2mm), with the cedar largely unchanged beneath, extra care must be given to the design of the project, the installation of the cedar and routine maintenance.

Without the protection provided by a coating against moisture intrusion, (especially end grain sealing), steps must be taken during the installation process to allow Western Red Cedar to readily dry following exposure to moisture, otherwise the risk of decay increases.

All cedar products used in exterior applications require a degree of maintenance to keep them looking their best. Even if the choice is made not to apply a finish to Western Red Cedar, contaminants such as dirt and mildew should be regularly removed to maintain its beautiful, natural appearance.

 

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