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  1. #1
    Join Date
    Dec 2009
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    Default Preventing rot in fence posts

    I'm installing a fence and arbor in my front yard. I'll be using pressure treated 4x4 posts, but have read many different ways people are treating the posts to prevent rot. I'm even considering using the Grace ice/water membrane that roofers use and wrap the posts with that below grade.
    Looking for some advice - or is the pressure treated good enough by itself to last me a good long time?

  2. #2
    Join Date
    Sep 2009
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    Default Re: Preventing rot in fence posts

    Modern day farmers dip the post in a 5 gallon bucket of drive way sealer to extend the life of there fence post. "Make sure the sealer dries before filling the hole".You can trowel roofing tar on the post also. We all know how hard it is to get that crap off.

    Drive way sealer is pretty cheap compared to replacing rotted post.

    Make sure you seal up just high enough above grade where standing water wont defeat your efforts.
    Gizmo

    Cut it 3 times & it's still to short.
    Inventor of the Miter Master Plus.

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  3. #3
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    Default Re: Preventing rot in fence posts

    There are additional options:

    1. Post base spike - you hammer it in the ground and your fence post is above ground., no concrete necessary. About $15 each.

    2. Post anchor or bracket, sits in concrete and the post is above ground. About $10 each.

    3. Metal post, like the one used for chain link, in concrete, then a 2x4 attached to it above ground.

  4. #4
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    Default Re: Preventing rot in fence posts

    Quote Originally Posted by dj1 View Post
    There are additional options:

    3. Metal post, like the one used for chain link, in concrete, then a 2x4 attached to it above ground.
    The post will rust off at the base if sit in Concrete
    Gizmo

    Cut it 3 times & it's still to short.
    Inventor of the Miter Master Plus.

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  5. #5
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    Default Re: Preventing rot in fence posts

    Quote Originally Posted by Gizmo View Post
    The post will rust off at the base if sit in Concrete
    Four options here: galvanized post, aluminum round post, square powder coated post and rust proofing paint.

  6. #6
    Join Date
    Apr 2012
    Location
    Northern Virginia
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    140

    Default Re: Preventing rot in fence (Metal) posts

    Asking a related question:

    I have several outdoor hand rails (6-9 ft. long) and a balcony hand rail (wraparound about 30+ ft/), all set in concrete and weather painted.

    But like Gizmo said, the feet are rusting away over 45 years. They have no feet cap protecting them. As they began to rust, it seems that "rings" formed around the corroding feet and increased accumulation of water around the feet. To my knowledge, the railings are not in danger of collapsing, but I would like to stop the corrosion process.

    What should I do.

    (1) With some posts, I suppose I can emory cloth them, apply new paint like a rustloeum outdoor paint, and caulk the base ? ? But what caulk would bond to concrete and painted metail ?

    (2) Other posts have corroded portions of the circular form, but still enough left to form a strong post. Any ideas to stop the corrosion at the feet?

    Thanks.

  7. #7
    Join Date
    Aug 2007
    Posts
    6,486

    Default Re: Preventing rot in fence posts

    Quote Originally Posted by Gizmo View Post
    The post will rust off at the base if sit in Concrete
    Not in our lifetimes.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  8. #8
    Join Date
    Aug 2007
    Posts
    6,486

    Default Re: Preventing rot in fence posts

    Quote Originally Posted by dj1 View Post
    There are additional options:
    Options 1 and 2 require the structure to be self supporting, perfect for the arbor, big problem with the fence. You can replace one or two bad posts in a line with this sort of repair, but you're relying on the integrity of the adjoining posts to do the heavy "lifting" as it were.

    Option 3 is the best for fencing but for God's sake, do not use chainlink posts! Those things are hideously ugly, for the same price or less you can buy a Postmaster post or Z post that is just as rigid and strong, just as durable, and doesn't require all the extra hardware to attach the rails. More over, because the posts are the width of the rails, you can run your pickets over them to cover.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  9. #9
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Preventing rot in fence posts

    Make sure the PT posts are rated for ground contact, not all are. Next, after the ground settles, go around to each post and pile dirt up at the base so it always sheds water away from the base of the post. Do this at least annually for a couple of years. Eventually it will harden up enough to keep the post dry all the time.

    If you decide to do concrete, and I personally do not see an advantage to it, fill most of the hole with your dirt, tamp it down good, then just fill the top two or three inches with concrete and taper it from ground level at the soil surface to about an inch up the post at the post.

    I recently pulled up a fence in my garden that I put out 25 years ago using PT posts. Only two posts showed any rot at the base and it was right at the dirt level, the ground had sunk a little at the base and I had never gone back and built up the soil at the base so it would hold water against the post. I have clay soil.

    So the short story is, keep water from pooling at the base of the post and you will be OK.

  10. #10
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Preventing rot in fence (Metal) posts

    Quote Originally Posted by t_manero View Post
    Asking a related question:

    I have several outdoor hand rails (6-9 ft. long) and a balcony hand rail (wraparound about 30+ ft/), all set in concrete and weather painted.

    But like Gizmo said, the feet are rusting away over 45 years. They have no feet cap protecting them. As they began to rust, it seems that "rings" formed around the corroding feet and increased accumulation of water around the feet. To my knowledge, the railings are not in danger of collapsing, but I would like to stop the corrosion process.

    What should I do.

    (1) With some posts, I suppose I can emory cloth them, apply new paint like a rustloeum outdoor paint, and caulk the base ? ? But what caulk would bond to concrete and painted metail ?

    (2) Other posts have corroded portions of the circular form, but still enough left to form a strong post. Any ideas to stop the corrosion at the feet?

    Thanks.
    As with the wood, you have to make sure that water cannot pool at the base, so it the concrete does not form a shallow dome around the base of the post, then you need to resolve that first. Also if the posts are open at the top, rain water will get inside the post an rust it from the inside out.

    Metal outdoors will rust in time, its a battle you will lose in the end. The trick is to delay the end as long as possible. After making sure the concrete is domed and the post is sealed, sand off any rust. The use a rust converter product like Naval Jelly. The main ingredient in the converter product should be Phosphoric Acid. Follow those instructions.

    Then put on a coat of a zinc rich primer. The only one I know of still commercially available is Zinc Chromate Primer from NAPA auto parts, but you will need to order it, most stores do not carry it anymore. It is classified as a carcinogen in California and probably by the feds as well. Wear a respirator when spraying. Then top coat with a good enamel. This will add years to the life of the post, but must be repeated at the first sign of new rust. Even with all this, those posts will eventually rust out to the point that they will have to be replaced.

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