The posts and rails shown are 20-year-old pressure-treated wood. Is there any maintenance that could have prevented the posts from decaying through the exposed end grain?

Is there any restoration that can extend the service life of the existing wood? E.g., I have heard of penetrating plasticizers that can shore up exterior wood.

Is 20 years about the expected service life of outdoor pressure-treated wood?

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When I reinforced my carport, I added pressure-treated 2x4 bracing. The ends were cut at an angle, so I sprayed on a heavy coat of Copper-Green® Brown wood preservative on the exposed ends, and let them dry, before assembling the reinforcement.

Copper-Green Brown will turn wood brown. This is exactly what I wanted; the resulting color matches the brown color of the rest of the pressure-treated carport framing. Other varieties are available, including "green" and "clear".

Copper-Green is for exterior use only. Only apply it in a well ventilated area; wear a mask to avoid breathing it; and wear eye-protection while applying it. Both the copper and the napthenate are toxic, so follow the labelling to "Wash thoroughly with soap and water after handling and before eating. Remove contaminated clothing and wash clothing before reuse."

It smells nasty, and the smell lingers for several days. (The smell does go away eventually.) The smell is because the product is copper napthenate. Napthenates are aromatic hydrocarbons that can make crude oil acidic. Napthenates help the copper penetrate the wood, and cause the copper to bond directly to the cellulose in the wood. This means the treatment will last indefinitely; it will not be washed off by rain. "It is not easily lost from the wood by leaching." The Material Safety Data Sheet (MSDS) is on-line.


I remembered a product my father made me use when working on some pressure treated framing for a gazebo. Pressure treating rarely penetrates 100%, so any cut ends or drilled holes tend to be the first point of more severe decay. he made me paint/cover any cut ends and drilled holes with a clear, smelly liquid. I believe it was called something like a 'clear wood preservative' and may have been made by 'Cuprinol'. It did not appear to work like polyurethane, but seemed to be truly a preservative, not a sealant (although they do make those also).

To his credit, this gazebo is still standing and shows nothing other than weathering.

I think anything like this rated for outside would help increase the lifespan of exterior wood.

It's also worth noting there are grades of pressure treated lumber, of which, I'm sure there are some grades 'better' than others at not breaking down. One of which would be 'UC5C' which is rated for direct contact to souther salt and brackish water (think dock building).

  • We used to stand posts in buckets of creosote before putting them in the ground. Some of those have been there 30+ years now. Of course, I don't think you can get creosote any more. Mar 17 '15 at 19:20
  • This could be another one of those tremendous products that worked BECAUSE it was so nasty, that the EPA said was just TOO nasty. Mar 17 '15 at 19:26
  • That stuff was definitely evil - got some chemical burns working with it with less care then I should have. Keep watching for skin cancer. Mar 17 '15 at 20:33
  • Creosote remains a common wood preservative for railroad ties and wooden telephone poles. Government agencies have established safe and dangerous levels of human exposure.
    – Ast Pace
    Feb 2 '16 at 21:59

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