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Tree roots pushing up steep driveway

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  1. #1
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    Default Tree roots pushing up steep driveway

    I have a steep pebblecrete driveway (see pictures) that has developed an issue where two of the large gum trees that are located right on the side of the drive are significantly pushing up the slab. This is causing a couple of issues; it not only causing the concrete to crack but also makes the drive even steeper and it now has a step at the steepest section. You can probably see it has also squeezed out conduits and water system from the ground.

    The photos probably don't do the slope justice but I have recently had to tow two delivery vans up the drive who have been stranded and am concerned that soon the drive will be unusable even for ourselves. Note skids marks in background

    I am looking for options to resolve the problem as it is only getting worse by the season. One of the trees is over 30-40m tall so am unlikely to get council approval to remove (could be wrong). I am happy to pull up a section of the drive but not sure if grinding the roots would result in the tree being weakened and falling (houses within meters). Equally I am not sure how the drive would be replaced so the same thing didn't happen again in a year or two.

    Any advice would be appreciated on both the tree and drive remediation issues. Thanks.


    driveway_1.jpgdriveway_2.jpgdriveway_3.jpg

  2. #2
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    You've answered you own question.
    Either the tree or the root has to go.
    The root is easiest so dig and locate the root, chop it off and chop a section out of it, then poison the section heading under the drive.
    In time the drive will settle back down as the root dies and collapses.

  3. #3
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    Thanks for the reply.
    Quote Originally Posted by cyclic View Post
    chop it off and chop a section out of it, then poison
    Part of my concern is what happens when you cut and poison the roots of a large tree? Is it likely to be structurally weakened and blow over in the next storm?

  4. #4
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    Quote Originally Posted by cyclic View Post
    The root is easiest so dig and locate the root, chop it off and chop a section out of it, then poison the section heading under the drive.
    What with?

  5. #5
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    Quote Originally Posted by Bros View Post
    What with?
    Chop with axe and or chain saw after digging around the root.
    Poison with the best tree kill you can get hold of.

  6. #6
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    Quote Originally Posted by Rexyboy View Post
    Thanks for the reply.

    Part of my concern is what happens when you cut and poison the roots of a large tree? Is it likely to be structurally weakened and blow over in the next storm?
    Maybe have a chat with an arborist.

  7. #7
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    Quote Originally Posted by cyclic View Post
    Chop with axe and or chain saw after digging around the root.
    Poison with the best tree kill you can get hold of.
    I didn't think you could buy the good stuff is small quantities (Tordon)

  8. #8
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    Isn't there a danger that poisoning the root will kill the tree?

  9. #9
    4K Club Member Marc's Avatar
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    There is only one way to resolve your problem and that is to cut the tree and dig out the stump, roots and broken section of the driveway and re do it.
    All other suggestions are dubious. Particularly the one to poison the root. Herbicides work systemically, that is they get absorbed by the plant and act on the whole not locally. You can sometimes spray the regrowth that happens at the base of a tree when you hit the root with a lawnmower and it starts shooting from the wound. But to cut a mayor root off and apply herbicide to the stump will either do nothing if you use Glyphosate, or kill the tree if you use Picloram.
    “It is not necessary to accept everything as true, one must only accept it as necessary”
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  10. #10
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    Quote Originally Posted by Marc View Post
    There is only one way to resolve your problem and that is to cut the tree and dig out the stump, roots and broken section of the driveway and re do it.
    All other suggestions are dubious. Particularly the one to poison the root. Herbicides work systemically, that is they get absorbed by the plant and act on the whole not locally. You can sometimes spray the regrowth that happens at the base of a tree when you hit the root with a lawnmower and it starts shooting from the wound. But to cut a mayor root off and apply herbicide to the stump will either do nothing if you use Glyphosate, or kill the tree if you use Picloram.
    By cutting a section, 6-8 inches, out of the root, the root is physically removed from the tree, it has worked for me twice, so I guess you would put that in the "got lucky" bucket.
    Of course there is always plan B of my advice, the tree has to go.

  11. #11
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    A root from a large tree on my front lawn was lifting the footpath. When grinding was no longer enough, the footpath was ripped up and relaid - the workers just cut the root off and relaid the concrete. I assume they used reo.

  12. #12
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    Cutting/poisoning a single root is not an option there in my opinion. There will be a number of decent sized roots 10cm or larger from a tree that size. Depending on species will affect how many are shallow.
    However from what I can see the main issue is the trunk/root ball raising the ground as it grows.
    Given the straight line I would say there was a expansion gap right in line with the tree. Now that its risen and dirt etc had a chance to get under it is unlikely to go down.

    As an immediate action I would get someone with a concrete saw/demo saw to cut back the edge from tree at least 300mm. That may slow the lifting.

    Looking at one of the pics there appears to be a house wall or retaining wall within 0.5m of the tree?
    I would identify the gum tree type and how large it will grow. See your local council and see if that type of species is covered from removal if its damaging structures.

  13. #13
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    I have a palm tree that has lifted the pavers. Will killing it off reduce the root ball so the paving settles back?

  14. #14
    4K Club Member Marc's Avatar
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    Quote Originally Posted by cyclic View Post
    By cutting a section, 6-8 inches, out of the root, the root is physically removed from the tree, it has worked for me twice, so I guess you would put that in the "got lucky" bucket.
    Of course there is always plan B of my advice, the tree has to go.
    If you cut the root, you don't need to do anything further. It is like cutting a branch off. Clearly it will no longer grow. However to expect the root to rot and the concrete to come down is wishful thinking. May be after 20 years of parking a M4 Sherman on the joint and the help of a few termite colonies may be so.

    It is a bit of a conundrum because if you ask the council and they say no, and that is the most likely outcome in Sydney, you have no other recourse. On the other hand there are new rules with trees that if they are within 10 meters of the house and endangering the house, you can remove it.
    With the palm tree ... I don't know how quickly will the palm tree roots rot. They hardly have any roots really. so maybe it is just the trunk? Palm tree are a menace, they drop all sorts of rubbish harbour rats and other pest and when they grow big enough they topple over in the wind straight on your roof or your car.
    To make matters more interesting the sap is so corrosive that the body of your chainsaw will be destroyed unless you wash it profusely after cutting the palm.

    PS
    Back to the OP tree ... if everything else fails, one could cut the concrete around the trunk and the root, leaving a gap on each side of the offending root, that seems to go across the path. Leave abundant room for the root to grow further and cover the trench with pebbles.
    “It is not necessary to accept everything as true, one must only accept it as necessary”
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  15. #15
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    I am cutting down a large multi-trunked bottle brush that is pushing over the front wall. There is already a crack in the wall so a stitch in time will hopefully solve nine

  16. #16
    Golden Member havabeer's Avatar
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    Get rid of the tree and roots.

    Apply to th council or don’t, it’s up to you. Is anyone around you likely to sob you in?
    Remember if you don't sin, then Jesus died for nothing

  17. #17
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    Big "widow maker" tree - never ever cut out roots, don't poison either. It'll be a ticking time bomb you and your family frequently pass under. The concrete will not settle back down as the root rots, it'll pretty much be "set" in place.
    If removing the tree is not possible you'll have to come to terms with having a drive with an in-built self destruct mechanism. You can articulate (with dowel joints or similar) the slab locally to minimise the differential movement, but you're probably always going to have a problem. Alternatively, build a nice little bridge/elevated driveway that meanders through your yard, maybe some switchbacks to reduce the slope...
    Edit: Forgot to mention legal ramifications if you did cut roots/poising the tree. I know a bloke who made the costly mistake of pruning a tree, it didn't fall over but he was fined and had to pay several thou to have it removed as councils arborist had declared it structurally unsafe.

  18. #18
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    As mentioned, cut out the section of driveway that's in trouble, but instead of pebbles I'd pack it with road base and expect annual maintenance. Or Asphalt the section, it is soft and will move somewhat, and may spread the need for maintenance but will cost more

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