2. HOW LONG DO WOOD DECKS, SHINGLES AND FENCES LAST?

When wood is exposed to the elements, its life span depends on the wood species, the degree of decay hazard, the maintenance activities, and the nature of the preservative treatment, if any. Shingles made of naturally durable western red cedar typically last 15-25 years. A well-designed and ventilated cedar deck will have a similar life, as will fence boards. A fence post made of untreated wood and put into direct contact with the ground is one example of a high hazard situation that will lead to a shorter life span. Properly treated wood can last at least 40 years – please see our page Performance Data for field test results on treated wood.

3. I’M BUILDING IN THE RAIN – WHAT HAPPENS IF WOOD GETS WET DURING CONSTRUCTION?

The wood will not be damaged by the water, but if the wood is too wet when it is enclosed into an assembly it will be at risk of decay. The National Building Code of Canada specifies that wood be at no more than 19% moisture content before enclosure – this is to provide a good safety margin against decay. How much water gets taken up by the wood depends on the circumstances.

Wood does not absorb water very rapidly from surfaces parallel to its linear cells – in other words, rain falling on the face of lumber or a panel will generally only wet the surface of the piece, and this moisture can dry readily. However, water is taken up more quickly on the ends of pieces. If possible, ends of lumber and panels should be more carefully protected from water uptake. Any wood sitting in a pool of water will eventually absorb some of it through any face, and this is a particular problem for sill plates.

The sooner a structure can be enclosed, and the roof can be installed, the better the chance for reducing this risk and increasing the time allowed for the wet elements to dry out. Wood that is over 19% MC needs time to dry before being enclosed. If the weather-resistant membrane (building paper or “housewrap”) can be installed as soon as practical, then the wood will be protected from further wetting as it dries while the rest of construction proceeds.


4. WHAT’S THE DURABILITY OF ALTERNATIVES LIKE PLASTIC WOOD?

Manufacturers of wood alternatives are quick to claim the durability benefits of their products over wood. Sometimes they’re right – wood isn’t always the best choice for every application. However, be wary of durability claims that aren’t backed up with long-term field test data. Plastic-wood composites may be more at risk of decay than advertised.