How to Repair Sidewalk Ruined by Roots by Lifting Concrete Flags

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Old 05-08-17, 05:09 PM
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How to Repair Sidewalk Ruined by Roots by Lifting Concrete Flags

I have a corner house with 2 big oak trees in front, and two on the side. All four are on the skirt of the concrete sidewalk. Three of the trees have uprooted the sidewalk to the point it needs repair.

From each tree, there are 4 flags (4' x 4' x 4") that have moved, and the outer two on each cause a pretty big lip which is why the repair is needed.

However, only one flag of the 12 has cracked, the others have simply lifted because of the roots.

Near me, a flag costs $150. That means $1800 to remove and replace them all. Yet, all but one flag is in perfect condition.

It seems it would make sense to lift each flag, chop away the roots, then put it back in place. And then just pour new concrete for the one cracked one. Easy enough--except for the 750 lbs they weigh. Actually, many are still connected as the flags are not installed separately, but have a line separating them. But I am guessing that a chisel and some movement will cause them to break apart at the line. Maybe that is what the line is for, for all I know.

I have looked for ways to lift them but every source I find explains how to lift sunken slabs just enough to shovel some sand of gravel underneath. I would need to lift each slab on its side, then lower it back into place after chopping the roots.

How would you guys handle this situation? Has anyone ever done this? Is it reasonable to consider?
 
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Old 05-08-17, 05:23 PM
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A walk behind mini skid steer (dingo) can be rented with pallet forks and should be able to lift 750 lbs. So that would be one option.

If you can figure out how to get straps under it using a bar and fulcrum then a portable hydraulic shop crane could lift them and would be a lot cheaper to rent.

You could use a bunch of pieces of pipe as axles and drag them out of place with a car or truck, although that would probably make a mess of the surrounding yard.

I would cut the control joints with a diamond saw before trying any of the above. Concrete has a habit of breaking somewhere else to protect the control joints
 
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Old 05-08-17, 05:47 PM
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it would make sense to lift each flag, chop away the roots
But then you risk the chance of killing the tree.

I think you have a situation without a solution unless you remove the trees, you can repair but eventually they will disrupt the sidewalk again.

Have you looked at the possibility of using foam injection to level it out, again a temp situation but less costly than replacing!
 
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Old 05-08-17, 06:13 PM
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I expect the roots to cause a problem again, which is why I dont want to sped big bucks to repair. Had it all repaired when we moved in 15 years ago, and probably could have had it fixed 5 years ago. So I dont expect more than 10 from any solution. Other than cutting the trees down.

Does chopping the roots kill the trees? I figure they have so many deeper roots, a few chopped away would not matter. That is what was done 15 years ago.

As for injection, that would not work. The problem is that the roots have lifted the flags, so they are already high... not low.
 
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Old 05-08-17, 07:20 PM
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Some trees are very sensitive to root damage, but I don't see that you have a lot of options other than rerouting the sidewalk around the trees (which I have seen for some very old, very large trees). If some roots were cut previously with no serious harm that is a good sign.

Different types of trees have different root structures; some have mostly fairly shallow roots. On those, cutting large roots can make the tree susceptible to toppling in a storm. Most varieties of oaks have their large roots within the first 3-4 feet of soil. They also have a center tap root.

An arborist could advise you regarding likelihood of killing the tree; they may suggest pruning the trees to compensate for loss of roots. But like I said, it doesn't seem you have many options. I would avoid removing more roots than you absolutely have to.
 
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