What is the average life expectancy of plywood siding?
Saturday, July 28, 2018
It’s difficult to assign a lifespan estimate to any wood product with an exterior exposure to rainy weather and humidity, because a protective paint coating that seals out moisture must be vigilantly maintained. If not, wood-rot fungal growth begins on the surface within weeks in the humid and rainy weather of Florida, and relentlessly eats through the wood over just a few years. Also, because plywood is manufactured by stacking thin sheets of wood with a laminating glue between them, the life of the adhesive is also a factor.
Our best estimate is 15 to 50 years, and here’s our list of factors that will shorten or extend how long plywood siding lasts:
1) The shortest lifespan we have seen recently was 15 years, and it appeared to be due to the wood not being adequately primed and painted initially, then not repainted as the original finish deteriorated at 8 to 10 years out. So a good coat of paint and regular repainting is important.
2) It’s also important to keep a good paint finish on the bottom of siding panels for two reasons: the bottom has end-grain wood, which is more absorbent of any water if not sealed, and the bottom of most panels is close the ground, where splash-back from rainwater falling off the roof onto the ground hits it.
3) Plywood siding lasts longer on houses with a gutter system that eliminates the rainwater splash-back against the base of the siding. Keep a maintenance alley between the wall and shrubs planted near the house. Dense bushes growing up against a home, like in in the photo below, keep the wall surface wet longer and promotes mildew, which will deteriorate the paint finish.
4) Many people replace just the bottom one to two feet of their plywood siding when it shows signs of rot and de-lamination at the base of the panel. This is fine as long as you install a “Z” flashing at the horizontal seam that is created in the wall. Otherwise, it becomes an opening for rain to get into and start a new wood-rot cycle. Just caulking is not sufficient. To read more about it, go to our blog post What is Z flashing?
5) Secondary areas where premature failure of plywood siding is also likely to occur are at corners and around window and door openings, usually caused by inadequate or deteriorated caulking letting rain water get behind the plywood. A professional painter knows that repainting a house means re-caulking too, but many homeowners skip that step. Be sure to caulk carefully when you repaint, check the caulk beads every few years to see how they are holding up, and touchup as necessary.
Go to our blog post What is the average lifespan of the parts of a house? for rating of other house components. To understand the basis, potential use, and limitations of lifespan ratings, see our blog post ”How accurate are the average life expectancy ratings of home components? Are they actually useful?”
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