What Can I Do About a Rising Sidewalk Slab?

Answered by Jeffrey ~ September 9, 2011 ~ Comments

One of my sidewalk squares has risen about six inches on one side. What could be causing this, and can I fix the problem myself?

Nevin H. ~ Des Moines, IA

Jeffrey Anderson

Hi Nevin. A rising sidewalk section could be caused by tree roots, the soil heaving from the freezing and melting process, or possibly some other reason. It's difficult to visualize how one section could rise six inches, which is quite a bit, without affecting the adjacent sections. Whether you decide to work on the project yourself or hire a contractor, the other sections should also be checked to ensure they haven't moved as well.

I'm also not sure what you mean about the water cut-off valve being located in the section of concrete slab. Normally there is a cut-off valve in the water meter crock at the street and the next cut-off is inside the house where the main enters through the foundation. It sounds like you might have some other type of arrangement there and it could be that a slow leak is causing the soil near the valve to freeze and disrupt the section of sidewalk. The water line in that area should be checked for leaks before any new concrete is poured.

If you're familiar with this type of work, pouring a section of sidewalk is definitely within the realm of a DIYer, but if you're not, I would definitely call in a concrete contractor. Sidewalks have joints in place so it's easy to remove sections in case there is cracking or movement such as you have. A concrete saw can be used to cut through at the joints and then the section can be broken up with an electric jackhammer and removed. It can also be broken up with a sledge hammer, but that's a little more work.

The cause for the soil movement should be investigated and remedied and then the area under the removed slab should be compacted and new gravel added if needed. I would also use a hammer drill to drill a few holes for rebar into the exposed edges of the adjoining concrete slabs. They only need to be about four inches deep and three in each slab should be plenty. You just want to use the rebar to tie the new concrete slab in with the old. Hammer pieces of rebar into each hole as far as they will go and four to six inches should be left exposed.

If you have never finished concrete, you might want to have a professional finisher do the actual pouring and finishing to end up with a good job. If you decide to do it yourself, remember to put a broom finish on the concrete as a final touch to provide some traction when the concrete is wet.

One Response to “What Can I Do About a Rising Sidewalk Slab?”

From the Reliable Remodeler Directory

You may be interested in these Iowa Home Improvement Contractors: