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Mud Jacking vs Foam Injections: What’s Best for Concrete Repair and Sinkholes?

Is your concrete sinking? Unstable concrete and sinkholes are a common problem in Floridian soils, and it can cause cracks and holes all over your property. Today is all about the best way of fixing sinkholes, and whether mud jacking or foam injections work best. Here’s what you should know about it!


Why does concrete sink?

Sinking concrete is a common issue here in Florida. The main reason why concrete sinks is because of unstable soil. Our sandy soil tends to settle over time, and the high water tables can create large air pockets under your slab. Eventually, this causes concrete to crack, break and sink.


Other reasons for cracked or uneven concrete slabs are water damage (due to broken pipes, for example) or lack of support for the slab (if part of it isn’t over soil).


To fix sunken concrete, we need to deal with two issues:

  1. Filling up current air pockets and settled spots

  2. Stabilizing the soil underneath the slab


To do this, most crews will give you two options: mud jacking or poly foam injections. But what are they and which one should you choose?


Mud jacking: how does it work

Mud jacking, also known as concrete leveling, is the process of injecting a concrete “slurry” underneath the affected slab to make it level. To do this, the crew will drill small holes into the slab. Then, the slurry is pumped into the holes and left to dry. Concrete slurry is a liquid mix of sand, cement and other ingredients. When injected beneath the slab, it can raise and level it.


This is a good option to avoid tearing out and completely replacing a concrete slab. However, the concrete slurry has relatively longer drying times, so it cannot get solid quick enough to lift very heavy or load-bearing slabs. It is also heavy, so unstable soils might settle down even more, creating air pockets that will destabilize your slab after the work is done.


Mud jacking is only effective on smaller slabs that have a relatively lighter weight, where the soil isn’t overly unstable.


Foam injections: how do they work

Foam injections follow a similar procedure to mud jacking, but uses a completely different compound to support the slab. After drilling penny-size holes into the uneven concrete, polyurethane foam is injected underneath.


Polyurethane foam is pumped in as a liquid, but as we inject it, it expands into a lightweight, solid and very strong foam. Because it expands on its own, it’s great to fill hard to reach air pockets in the soil and perfectly fills cracks.


Poly foam injections are nowadays the preferred method for fixing sinkholes and uneven concrete. High-density polyurethane is strong enough to lift very heavy concrete slabs, and works even in load-bearing areas. Plus, because it is a synthetic waterproof product, poly foam holds up better than mud jacking to weather damage and can be used in projects near the water.


This method has a ton of benefits: it supports concrete, levels up slabs, it’s flame-retardant and water resistant. Being so lightweight, it won’t compact your soil even further, unlike mud jacking that tends to make soil settle over time. Poly foam injections are also useful to give structure to unstable soil: it adds no extra weight and binds the soil together, meaning your slab will have a proper base to lie over.


Foam injections vs mud jacking: which one is better?

As with most tools for concrete repair, there is no one-size-fits-all answer. Some projects are suited for both, but others will only work with a specific technique.

In our experience, mud jacking has a limited application scope. This means fewer projects will require this technique. As we’ve mentioned, mud jacking adds extra weight to the soil, which might weaken the ground even more. This can lead to sinking over time!


We would only use mud jacking in these cases:

  • Concrete that is still in good condition but no longer level

  • Smaller slabs that weigh less

  • Concrete that doesn’t need to be used right away because of longer drying times

  • Projects that won’t have contact with water


On the other hand, poly foam injections can be used in a wider range of settings. Our team has used “poly jacking” for sidewalks, driveways, pool decks and many other uneven concrete projects. In our experience, poly foam injections work better for:

  • Projects where time is essential: there is almost no waiting for it to dry (you can put weigh on the concrete after 30 minutes). Poly foam is also faster because there is minimal cleanup. Unlike concrete that we have to mix and then scrape off, after we’re done with poly foam we’ll just dust off the surface and everything will look as good as new.

  • Fragile concrete: poly foam adds almost zero extra weight, avoiding further damage to the concrete slab. Try using poly foam to even out your concrete instead of pouring anew!

  • Heavy or load-bearing slabs: polyurethane expands to reach every nook and cranny, and then dries into an incredibly strong foam. The high density of the foam can lift very heavy slabs and offers further support to load-bearing concrete.

  • Concrete or soil that will be in contact with water (like pool decks or beachside properties)

  • Large sinkholes: poly foam is a quick and cost-effective way of filling up sinkholes and providing a stronger structure to the soil.

  • Projects where looks are important: poly jacking requires fewer drilling holes than mud jacking.

  • Poly foam injections also last much longer, compared to the usual 2 to 3 years for mud jacking projects.

In our experience, poly foam injections provide better value to our clients, since the job lasts longer, it looks better and can withstand contact with water. A clear winner in our book!


If you’re still unsure about how to fix your concrete, we’re here for you! Let us know your questions and our expert team will give you tailored advice.

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