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Look to interior for source of moisture that causes rot

Gustavson, M.
2000
Times, Jan 29, pp. A18


Gustavson, M., (2000), "Look to interior for source of moisture that causes rot", Times, Jan 29, pp. A18.
Abstract:
It is possible that exterior claddings have some omissions of flashings, or joints may permit the entrance of moisture from rain, etc., but I doubt if any tradesman would deliberately do a job to the extent that is claimed as the cause of all the rot and decay reported. Nor can I comprehend that all exterior cladding is being installed faulty by so many tradesmen, at the same time.

To stop the movement of air laden with moisture from entering the exterior walls and ceilings, a vapour barrier, normally polyethylene, is applied to the innermost face of the exterior walls and ceilings prior to the application of the gypsum board or similar finishes.

Now, to come to the crux of our problem. Some of the moisture- laden air is getting through the polyethylene vapour barrier, either through holes, or damaged polyethylene, or where there is no vapour barrier at all, and condensation occurs within the wall cavities. Also, the exterior sheathing and cladding is subject to exterior weather temperatures, particularly where it is exposed to rain and wind. Condensation will collect here more readily, which will be absorbed by the wood framing materials and insulation, providing ideal conditions for the development of fungus, mould, and decay -- hence rot.


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