Frequent Rains: Another Decay Hazard for Wood

In Build Green: Wood Can Last for Centuries, Carol Clausen and Sam Glass remind readers that moisture causes wood to decay, and another source of moisture that the homeowner must guard against is frequent rains.

The natural hazard for decay of wood used above ground is greatest in regions with high rainfall and mild climate. In the contiguous United States, this occurs in the Southeast and Northwest.


The map shows three zones of decay hazard in the United States.

What does that mean for the homeowner? Remember–the decay hazard for homes is greatest on the side that is exposed to prevailing rains. This is most noticeable in the region of highest decay hazard, where greater precautions against decay may be needed on the more exposed side of the house than on the remaining sides.

Interestingly, this photo shows that a high-decay hazard can even be artificially created when wood siding is repeatedly wetted by a lawn sprinkler, faucet, or vegetation that is planted too close.


With proper attention, treated wood, and building techniques, the homeowner can guard against the threat of decay from frequent rains even in the most rainy locations.