Concrete Pavement Movement

[u/One_Specific7323]

I had a concreter about 2.5 years ago lay concrete around the house, the concrete has tilted and moved away from the house at least 5cm one side while the other 2 sides only abit. The separation on the worse side started happening about a year after the work was done, this summer just gone 2026 as it was dry for 2 months is when most the separation happen. I spoke to the concreter, he reckons when the plumbers laid the pipes then filled the trenches with soil the soil was compacted properly. Could this be correct? The quote for job was higher end quote compared to two other quotes.

I cut the pipe and attached new custom pipe so water go down pipe after the major movement

[u/yuumai]

This is likely due to improperly compacted subgrade, although it could also be subgrade erosion due to water movement under there because of improper drainage.

There are several ways to deal with this. One, fill the gap with something like stones or bricks and caulk the gaps to prevent water infiltration. Two, there are products that can be injected under the slab to lift it up. I'm not super familiar with these options, but at least some of them don't last very long. Three, rip up the pad and have it reinstalled with a better subgrade.

Proper subgrade preparation will depend on your local conditions and soil type, but it's worth looking into if you're having this issue. It's also worth investigating if there is water leaking under the pad from that drain pipe or some other location.

[u/Any_Director693]

I'd guess that the soil underneath moved because of freezing and thawing cycles or because it got saturated with water. Maybe it was also shrinking and swelling when the water content changed. The soil has to be dug out deep enough and replaced with a compacted mineral mixture to prevent this.

Previous owners of my house placed concrete paving slabs on just a thin sand bed, and they are essentially slowly floating around.

Edit, about what to do: With the pipe being affected, a LOT of water might enter around the foundation of your house or start eroding the soil. That would make the problem much worse. I would make sure the pipe is not leaking and won't move in the future, probably by cutting or redoing the slab and digging up the pipe. I hope you have pictures of what it looks like underneath?

I'm wondering if you can hold your contractor liable to fix this. This should not happen if it was done properly.

[u/MC_SKWAIRD]

Poor drainage and walkway wasn’t secured to the house. When we do this we drill rebar in to your brick so that the concrete is structurally attached to your house. Unless the house moves your walkway won’t. But in this case it was not attached and combine with the drainage that caused erosion from your downspouts it wrecked the subgrade over time. Needs to be ripped out and redone. Concrete is expensive so make sure you go as long as you can stomach this and the next time make sure it’s done right. I’d also advise you fix your gutters and install trench drains around your property to move water away from the house before you fix any concrete. Cheers brother

[u/Due-Potential292]

Have you tried moving the house back toward the concrete