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H4 Treated hardwood in concrete - will it rot?

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  1. #1
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    Unhappy H4 Treated hardwood in concrete - will it rot?

    I'm building a backyard office/cabin/shed/cubby house and in my usual form, I got excited and jumped right into it. Before you know it I had built the foundation and concreted everything in. I then woke up in the middle of the night worried that I've done it wrong, so I did some Googling and it says to never concrete posts into the ground because they will rot.

    So, I have concreted 100x100 H4 treated hardwood posts into concrete footings. Pics attached. Are these really going to rot? My soil is not completely dry, this is at the top of the yard and won't have water pooling here, but it is in Queensland and we get a fair bit of rain.

    My 'office' is 4x4, timber frame with a skillion roof and corrugated cladding. No plumbing, technically just a nice shed.

    I'm worried I now have to jackhammer what I've done out and replace with steel posts. What are your thoughts?
    Attached Thumbnails Attached Thumbnails pxl_20210608_211327176.jpg   pxl_20210608_210841652.jpg  

  2. #2
    3K Club Member johnc's Avatar
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    I would put in steel, hardwood will have a life but also will rot. A lot easier to replace now before you build

  3. #3
    Community Moderator phild01's Avatar
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    I wouldn't be too worried if there is aggregate at the base of the posts. A lot depends on ground conditions too. If you concrete in zinc steel you need to consider the corrosive effects of the concrete.

  4. #4
    4K Club Member Marc's Avatar
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    That's a conundrum. You believe it is wrong, and so would like reassurance to the contrary

    The post will rot, especially because the water soaked timber has swollen and cracked the concrete before it set completely ... the question is how long will that take.
    I remember a pergola post in concrete that was still standing after 20 years fully exposed to the rain. Hard to tell.
    You can double up for peace of mind. Get 8 stirrup,the one HDG with solid stem, (Paint the stem ) ... dig 8 holes, screw the stirrup to the bearer and let it hang in the center of the hole. Concrete the stirrup and you will have footings that are hurricane proof
    And peace of mind for little money, and best of all, you will not need to undo what you did.
    The italians say "Fare e disfare è tutto un lavorare. "
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
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  5. #5
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    My untreated hardwood fence posts only lasted 25 years, I thought they may have lasted a bit longer. I blame the wife for watering the grass too often.

  6. #6
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    Quote Originally Posted by PhilT2 View Post
    My untreated hardwood fence posts only lasted 25 years, I thought they may have lasted a bit longer. I blame the wife for watering the grass too often.
    This is what I'm thinking, I'll be gone before then.

  7. #7
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    Quote Originally Posted by Marc View Post
    Get 8 stirrup,the one HDG with solid stem, (Paint the stem ) ... dig 8 holes, screw the stirrup to the bearer and let it hang in the center of the hole. Concrete the stirrup and you will have footings that are hurricane proof
    This is a great idea, thank you very much. I feel better already. What paint should I use for the stirrup stem?

  8. #8
    4K Club Member Marc's Avatar
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    If it is hot dip galvo, etching primer and oil based top coat, but anything else will do too. I used bituminous roof paint with good success.
    Whenever you find yourself on the side of the majority, it is time to pause and reflect
    Mark Twain

  9. #9
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    If you are really worried, on the inside and out of view, simply dynabolt a HDG angle on 2 sides to the concrete and bolt to timber above ground level.

    Because you have put an edge up, water wont pool, so rot if its starts will start from the base of the post - personally though its not how I'd do it, i wouldnt remove and start again.

    The other option is to put another hole 400mm back from the corner under the bearers and stick 2 bags of concrete in it - either leave it flat so its an option in the future, or put a half stirrup supporting the bearers (i think this is sort of what Marc is talking about but I am unclear)

  10. #10
    Je pense, donc METRIX's Avatar
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    I wouldn't worry about it, you have done a good job with the concrete by creating a pad above ground, this wont allow water to easily find it's way into the join between the timber and concrete.

    What's done is done, leave it as it is and it will probably be good for 15 - 20 years, next one you build substitute the H4 posts for gal stirrups.
    Mieux vaut prévenir que guérir

  11. #11
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    Agree with Metrix. Don't waste time and effort trying to rectify. What you have done is OK and better than what many would have done. If, at some time in the distant future you have to redo it, fix it then.

  12. #12
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    Quote Originally Posted by Bluesrule View Post
    Agree with Metrix. Don't waste time and effort trying to rectify. What you have done is OK and better than what many would have done. If, at some time in the distant future you have to redo it, fix it then.
    first rule of the internet - once you have done the thing, dont go researching about the thing.

    Its like buying something - its done, dont look at prices anymore-you only get disapointed

  13. #13
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    Thanks for all the feedback guys, I've continued building the frame and it looks like it will be pretty easy to fix down the road by just adding extra stirrups then, if necessary, so I'm going to leave for now.

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