Jacking sidewalk slab (what to put underneath)

[John Mack]

Hello, I have two sidewalk squares that the city has marked as needing to be replaced (at their cost of $400-ouch) or leveled/repaired by the homeowner(me). So I decided to try and jack the squares up today(see pics) and was successful in getting them pretty level. Now my question is what/how do I put in the gap under the side walk to keep it there. I thought about trying to pound sand in with a wooden dowel but that seems like a slow process,I also thought about trying to pound in wood or metal shims along the side of the slab or fabricating some type of device to hold the slab level and then try to work mortar into the void and just leave the device in the mortar. If anybody has any thoughts on what would work best I would really appreciate your help. Btw after the repair is complete I have to get it inspected by the city so I will have to try and make it a well done job so I just can't jam a rock in each corner like I wanted to do. Thanks in advance for any advice given.

 

[Rookie2]

sand, concrete, gravel

you will have to dig out most of the low side , the corner will not hold the weight of the whole slab. jack it up a little higher than level then backfill , it will settle.

 

[In The Doghouse]

In because I have the same problem with a sidewalk slab.

 

[Kevin54]

Wedge some bricks under it, or make a form and work some concrete under it.

 

[SteveCh]

Wedge some bricks under it, or make a form and work some concrete under it.

Or both. Get the bricks set in place securely and build a form and pour concrete in around the bricks. Just one idea.

 

[James-W]

Digging down so deep like that to use a hydraulic jack seems like quite a bit of work, not to mention filling everything back in again when you are finished. Is there a reason why you couldn't use some pry bars to remove that section of sidewalk, then use sand to fill in the low areas? Once it is level, put the sidewalk section back in place again. I would think that would be a lot easier and quicker.

 

[Techie1961]

Kind of curious why you would do it yourself. Was it just for the learning? I have never heard of a city allowing a homeowner to repair something like that. The unions here in our municipality would probably fine me.

 

[PT Doc]

Maybe by letting the homeowner repair they are meaning getting a contractor by yourself. Mud jacking works because the mud finally fills all the voids and raises the concrete. You have opened up both sides so the clear option is rigid support but you will have lots of void space between the rigid piece of rock or whatever you choose.

 

[brownbagg]

dont wedge with bricks, that just stupid, don't use wood, don't use metal shims. just repour it, it hell lot cheaper, quicker and quality. if you have to jack it to keep in the face of god, then use concrete to jack it with.

 

[southalabama]

Anything short of a new pour your gonna have problems especially during the next freeze and thaw.

 

[John Mack]

Thanks for all your suggestions. I took them all into account and ended up jacking up the slab on the low side and working sand in with a metal rod. At the end of the day this was a lot of work but I was satisfied with the end result. I am aware that this is temporary repair but if it buys me a couple of years I will have considered it worth the effort.

Kind of curious why you would do it yourself. Was it just for the learning? I have never heard of a city allowing a homeowner to repair something like that. The unions here in our municipality would probably fine me.

Thanks for your reply. I wanted to do this myself because as stated the city wanted $400.00 to replace the two slabs.

Digging down so deep like that to use a hydraulic jack seems like quite a bit of work, not to mention filling everything back in again when you are finished. Is there a reason why you couldn't use some pry bars to remove that section of sidewalk, then use sand to fill in the low areas? Once it is level, put the sidewalk section back in place again. I would think that would be a lot easier and quicker.

I thought about pry bars but I did not have any big enough and the other issue was that both squares were re-barred together so I would have had to lift both at the same time.

Anything short of a new pour your gonna have problems especially during the next freeze and thaw.

I agree, the city has a three year cycle of inspecting the walks and if the slab settles and fails inspection on the next cycle three years from now a new pour is what I am planning.

 

[WVBrady]

I'm in too late, but what I would have packed in instead of sand would have been dry concrete mix. It will gradually draw moisture and get very hard. If the sand starts to fall out and cause a hazardous condition, you might still try that.

 

[Worsedog]

I used the concrete mix method to lift a porch that was settling. It had settled enough to open a 1/4 inch crack across the slab. We dug down enough to put a little floor jack under it after digging under the slab as far as we could easily reach with a shovel. Then we dumped Sakrete under the slab and pushed it back with a 4x4. We also misted it just a tiny bit as we pushed it under, then packed it hard by pounding the 4x4 with an engineers hammer. Did that about 8 or 10 years ago and you have to get on your hands and knees to even see the original crack. Of course the ground never freezes here, so that might not work for you.

 

[Strouty]

Your biggest problem will be the frost, but if they are going to inspect it this summer and then again in three years you should be fine. It will most likely look like hell next spring since you dug out all the undisturbed dirt that had been compacting over the years, but you wanted to buy some time and that is what you will get.

 

[Saw]

Kind of curious why you would do it yourself. Was it just for the learning? I have never heard of a city allowing a homeowner to repair something like that. The unions here in our municipality would probably fine me.

It's Green Bay, their all in!

They all own the Packers too!

 

[toolmiser]

I know this is a done deal, and I could be completely wrong, but I think I read or heard that for something (low load weight) that they use spray foam?