Lifted sidewalk - pouring a partial slab

[JHZR2]

I have a sidewalk at one property, that has a corner lifted up in a peculiar way. The whole sidewalk is straight and flat, but one corner of one piece is lifted up about 2” due to roots and dirt. It’s an equilateral triangle corner of the sidewalk, about 2’ on each side.

This piece of sidewalk is also part of the driveway apron system, so it matters thst it’s raised as it affects maneuverability over it.

My wife and I pulled it today. It’s all because of a tree root and excess dirt underneath. We dug out a lot of the dirt, and chopped at the root, but it wasn’t enough.

We got it back in place but it isn’t stable, and isn’t much lower. Sure we could chop the root more, but I’m still not sure we would get the best result. So we are weighing the option of just making fresh concrete, putting loose rocks in the bottom, and pouring and working it flat.

I get it that the tree root could lift this too. But at least we could make it flatter and more stable for now.

Since it’s all jagged right now, whats the best bet? Cut the concrete with a saw or chisel to make a perfect straight edge? Create a boundary between old and new?

 

[Langanobob]

A photo would help,

 

[SHOZ]

Use a reciprocating saw and a wood blade to cut out the root.

 

[demarpaint]

Use a reciprocating saw and a wood blade to cut out the root.

That's what I've used, I dug the area deep and wide enough not to be sawing into dirt, made cuts and used a pry bar to get the root out. Once done I used rebar and did the concrete work. Last I looked it is 27 years and still holding.

 

[JHZR2]

A photo would help,

This is where it’s at. I pulled it knowing that it might not go back together. The big piece is teetering on the root still, which I chopped away a bit, but not enough.

It’s part of effectively a double width driveway apron, so there’s concrete on both the building and street side. All of that, and the rest of the sidewalk on both sides are good and flat.

It’s old concrete. 50+ years I’m sure. I kind of want to keep it in place since new concrete is ugly white and never seems to last as well. But I get it that in this situation, a patch may need to be poured.

 

[spasm3]

If I wanted to keep it, I'd pull up that whole square of concrete. I'd rent a stump grinder and take the root out, then use sand to level out and place the pieces back.

 

[JHZR2]

If I wanted to keep it, I'd pull up that whole square of concrete. I'd rent a stump grinder and take the root out, then use sand to level out and place the pieces back.

I don’t disagree. That was part of our thought, to get more out and get sand underneath.

We had to close it up yesterday because of a torrential thunderstorm… but can revisit it again to do that.

 

[y_p_w]

Could be worse.

My parents actually got a correction notice from the city about the sidewalks in front of an investment property. Apparently any difference of more than a half inch is considered a nuisance that needs to be corrected. I suppose it could be redone, but apparently the most common way to correct it is by "shaving" the concrete. The sidewalks were probably done about 60-70 years ago, and most of it doesn't appear to be from roots, but just normal settling of the soil.

I was asked to help them out with this, and found out that these notices only come when someone complains about it. I talked to a few neighbors who said they never got any similar notice, even though their sidewalks were even worse in terms of being uneven.

And this city is really a pain to deal with. They require an encroachment permit since this is considered a public right of way. That on top of requiring a city business license and proof of insurance in order to get the permit. I heard it might be a $500 job in other places, but with all the hoops to go through, the cheapest my mom could find was about $2000, plus the cost of the permit. The permit was about $1300, but with about $1000 refunded upon satisfactory completion of the job. I called up a company (that advertised this kind of work) to see if they'd be willing to come over. I wasn't quoted a price, but they said they would normally just find time in a day when they were already doing major work and it would be pretty easy. And that city (which is known for otherwise onerous permitting) didn't require a permit for minor sidewalk repair as long as the contractor has a state contractor's license. Several contractors said they'd either charge extra to get the license and specific insurance, or they flat out said they couldn't do it.

I'm guessing that someone who might take of this before the city gets a complaint might be able to do it quickly and cheaply.

 

[Pablo]

Just needs dug out and replaced. Tree cut back.

No reason new concrete will be weaker, or uglier.

THAT looks terrible. IMO.

 

[JHZR2]

Just needs dug out and replaced. Tree cut back.

No reason new concrete will be weaker, or uglier.

THAT looks terrible. IMO.

In general I find new, modern white concrete to be ugly. Old concrete had more aggregate or something and looks better to me.

More or less all the new concrete I see spalls and looks bad in a few years. Maybe that happened to the old stuff, just way long ago.

I’m not saying a cracked and lifted triangle looks good. It doesn’t.

 

[Pablo]

In general I find new, modern white concrete to be ugly. Old concrete had more aggregate or something and looks better to me.

More or less all the new concrete I see spalls and looks bad in a few years. Maybe that happened to the old stuff, just way long ago.

I’m not saying a cracked and lifted triangle looks good. It doesn’t.

Yeah some mix companies definitely push the limit and go cheap. I have a couple guys who know structural concrete. No watering down or low on cement right size aggregate

 

[SHOZ]

I'd take it out and dig out the root then like said get some sand and put back in place. My driveway extra parking area looks the same. For the same reason. Last winter I dug along it and cut the roots. Some 3+ inches thick, white pine and oak. Left them under the cement. Mine are not raised just busted up.

 

[spasm3]

I don’t disagree. That was part of our thought, to get more out and get sand underneath.

We had to close it up yesterday because of a torrential thunderstorm… but can revisit it again to do that.

I can see why you want to keep the old pieces, color matches, the surface texture matches which is harder to match with new concrete. Hard to keep new concrete splash , drips off surrounding concrete when leveling , floating.

If you removed the pieces and just poured new concrete thats thinner , so the top was level, i think it would crack again in short order, even with a fiber mix.

I would get plenty of root out, only concern is if you can get it all with a small stump grinder, due to surrounding concrete.

You might have to sacrifice a chain saw chain and possibly the bar, to cut it out of the dirt. Use a cheap chainsaw!

 

[TheLastWord]

Is it an actively growing tree?

That will just create the same problem?

 

[JHZR2]

Is it an actively growing tree?

That will just create the same problem?

Yeah that’s my point above.

I chopped the root some. It needs to be ground more.

And if I pour more in there, I suspect the root will lift and crack that too.

 

[SHOZ]

If you cut a large root off make sure it's a couple feet back from the concrete. The root will sucker out tiny rootlets but not become big again for years.

 

[facility1]

remove all adjacent bad concrete,,, get a reciprocating saw and use a long pruning blade(s) , cut all roots on both sides of walk a good foot plus out ,then grub out roots (pick axe) that you sawed (or chop off with axe),,set some forms (2x4),,and pack down ground ,a heavy sod tamper works ,add some gravel or base course ,tamp again, level, next mix up come concrete in wheelbarrow with a hoe ( get the high psi concrete mix in bags),or call ready mix truck using six bag mix,pour in form strike off with a 2x4 then trowel off & smooth (or use a float),, then brush surface with damp cement finishing broom after it set for about 15 minutes ,cut in edging sides with special tool, and expansion seam tool . (harbor freight has a set of cement finishing tools), if you want a bit darker color to concrete get some dirty dusty sand, like sweepings from garage floor etc., add a small amount to mix, as this will darken cement mix a bit.

 

[Astro14]

If I wanted to keep it, I'd pull up that whole square of concrete. I'd rent a stump grinder and take the root out, then use sand to level out and place the pieces back.

That’s what I would do…

 

[spackard]

For a quick fix you might get away with rubber pavers. 24x24 listed for $20 at HD. Use a grinder to cut to size.