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I'm resurfacing a deck. It was built 19-20 years ago. Had an inspection and was recommended to replace 4x4 direct-bury posts with 6x6 with concrete piers/footings. This work isn't as simple as jacking the deck and digging (sistered boards against 4x4s, posts right against foundation, stone pavers and drainage pipes to deal with; not to mention 30"x22"x22" dig with 70 bags of concrete). The posts are currently fine after 20 years. I'd rather just leave it and deal with replacement in 10-30 years. But is there anything I can do with existing buried posts to extend the life? There are some related answers (only 1 for existing, and none discussing post protectors) and looks like my options are:

  • post protectors - no mention of using these post-construction to extend life
  • blueskin around the posts
  • concrete - not recommended because of 'collar rot'
  • packed gravel around post - haven't seen any mention of this

Would a post protector work to extend the life (I would probably have to cut it to get it around the existing buried post) or would any other alternative work better? at all?

Post Protector

Post Protector

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This answer assumes the deck is in a good shape and the recommendation for post replacement was not from the City inspector for permit concerns.

I may try to open the buried post, let it (skin) dry then coat it with a layer of hot asphalt (in liquid form), the more the asphalt is absorbed into the wood, the better the performance of repelling the water/moisture. Clean gravel is a good idea, but if the existing soil already posses free-draining ability, I won't bother with it.

Since the deck has already stood for almost 20 years without problems, I won't replace the post unless it has damages such as cracks, or aging (wood softening below grade). If necessary, add a bracket on the beam-post joint, or a diagonal in between posts can be as effective as a larger post.

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  • Thanks for the answer @r13 Dumb question: how does one go about coating with hot asphalt? Is this a DIY job? Some equipment I need to rent? Any opinions on the PostProtector linked?
    – Joe
    Oct 11, 2021 at 16:01
  • Also If I do use gravel, should it be pea-sized or 3/4" or something else?
    – Joe
    Oct 11, 2021 at 16:48
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    1) The asphalt needs to heat to a high temperature, I don't think it is a DIY job, but a roofer or similar trade that has the equipment ready. I would suggest taking the alternative route - apply wood preservatives (see the link below). 2) I personally prefer pea gravel, because it needs the least effort of compaction. You can use gravel graded for foundation use, but you need to pay attention to the rate of compaction to achieve densification. archtoolbox.com/materials-systems/wood-plastic-composites/…
    – r13
    Oct 11, 2021 at 17:13
  • There are a lot of wood preservatives on that page. Is there one (or several) that you recommend?
    – Joe
    Oct 11, 2021 at 18:16
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    I suggest looking for an oil-based preservative that is suitable for underground use (I think most of them are). Just read the description to get some idea. Also, you shall check the availability around your local stores. It wouldn't hurt if you check with your lumberyard, they will be able and glad to offer help.
    – r13
    Oct 11, 2021 at 19:19

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