Superior Process - What does tried and true mean to you?

Natural Limestone Grout - VS - Chemical-Based Poly-Foams: Our Experience & Research

Many of our customers have asked about the use of chemical based Polyurethane Foams and what our position is on that material and process. Hopefully the following information will give you some insights as to why we will only maintain the tried and true use of Limestone Grout foregoing any future use of chemical based Poly-Foams.

As western PA’s original pioneer of concrete leveling, for 20+ years On The Level, Inc. (Your local A-1 Concrete Leveling operator) has only used an environmentally safe Limestone Grout material to perform the lifting and leveling of sinking concrete. We call ourselves a “Foundation Repair Company” not only for the ability to repair foundations and to repair sinking concrete but all of our solutions solve issues with what’s going on underneath. We have extensive knowledge and experience with the soil makeup of the western Pa region. Drawing on that time in the field provides us a thorough perspective on how to properly resolve problems our customers deal with.

We equally pride ourselves in being an environmentally compassionate company and maintaining that trust is very important to us. Our customers feel vested in our approach knowing that they are utilizing a process that replaces lost earth due to erosion, poor drainage or compaction with more solid earth.

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The Benefits of Limestone


Limestone is actually used as the base when new concrete is poured. We feel if limestone is the perfect material for pouring new concrete on, it has to be an equally perfect material for filling voids, re-establishing the base and lifting existing concrete that has sunk.


One of the pieces of mis-information that is circulating by foam competitors is that the weight of our material causes further sinking. Limestone is 80lbs per cubic foot, by comparison, an 80 pound child standing on one foot on top of a slab exerts 40 times more ground force vs what it takes to lift a 4x4ft slab with our material. Weight is a non-issue. 40+ years of leveling history and mathematics does not support any other conclusion.


The flow-ability of limestone allows for a superior result filling unevenly developed voids under concrete slabs. Re-establishing the entire base under a sinking slab is critical in providing a long term solution that doesn’t put the slab at risk for future cracking where a void with no leveling material exists.

The Natural Choice

1% of revenues are donated towards sound environmental initiatives

Our customers are essentially partners in that endeavor

More Benefits of Limestone


Limestone does not over-react or over expand, running the risk of “over-leveling” a slab due to moisture that is unseen underneath it. With limestone, we can change the flow-ability/viscosity of our material instantly so we can lift or stabilize as we want giving us on the spot versatility. We can control the lift throughout the entire leveling process.


Our material can be injected through either size delivery method and the needs of the project determine which option is used.


We have never in 20+ years of limestone leveling seen any evidence of infestation of any kind taking place. Polyurethane foam on the other hand does offer the risk of infestation evidenced by the video below.


Once our material sets up and becomes hardened underneath the slab and if there is no more ground erosion under our material, our process provides a permanent solution.

Customer Reactions!

Rating: 5
Testimonial (Short):

They guys came out. They got right on it. We've had no issues. I would absolutely recommend it. As a matter of fact, I'm considering having some done at my house. It looks better as well as being more cost effective.

From: Sean (contractor)
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Rating: 5
Testimonial (Short):

We were facing a basement wall with fairly significant separation in it. The concrete block had moved and opened about an inch / inch and a half across about 15-20 vertical rows of block. I was very pleased with how the gap in the block closed back up. Traditional companies had wanted to charge me more and would not guarantee that my existing wall would not continue to deteriorate. Whereas A1 added a new structural component to it, putting rebar into the block and putting cement mix into the block. All which I saw were truly improvements to a 50 year old concrete block wall. My overall experience with A1 was excellent in all ways.

From: Steve (homeowner)
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Chemical based polyurethane foam: Our Concerns


The components of PolyFoam only become “inert” when mixed precisely and exactly right, otherwise individually are toxic. If the individual components spill due to a loose connection, bad O-Ring or worn tool, the exposed items will need replaced or at a minimum painted. The chemicals cannot be washed off.

How Is It Made?

The product is formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups) with a Di-Isocyanate or a Polymeric Isocyanate in the presence of Amine based catalysts and additives. Amine catalysts are widely employed in foundry and polyurethane foam operations. These highly reactive Amines have been associated with graphic disturbances in vision and other respiratory health effects.

Potential Risk

If the “A Side” and “B Side” chemicals that come together at the point of injection under the concrete are not properly calculated, there is potential for what is called “Off Gassing” or the airborne release of the reactants to occur for a span of time after the project has been completed


Voids that produce sinking slabs are usually never evenly distributed or consistent. They have peaks and valleys and the visual symptom at the ground level is never the entire story as to what is going on underneath. Foam sets up relatively fast and due to that nature, the foam material often fails to spread evenly enough to re-establish a significant area of the base. Foam is done in a series of injections with the second one setting up under the first injection and so on (like a stack of pancakes). This creates a pyramid or localized pillar type effect under the area that has sunk to raise it back up. The issue at ground level may seem to have been solved but the lack of spread underneath puts the rest of the slab at risk for future cracking where there is an unfilled void and no material.


Foam reacts and expands with moisture. Lifting concrete with foam often requires a “stop-short” approach. Due to the potential of unseen moisture under a slab, lifting and stopping just shy of level is usually the means to guard against over lifting. Once a slab is over lifted it is an irreversible situation with the more expensive option of replacement being the only customer recourse. Due to the relatively fast set up nature of foam, tamping a slab back down once over leveled is incredibly difficult.


For smaller projects this is acceptable but for more detailed work or larger slabs additional 5/8” holes may be needed to achieve the desired outcome. Our customers always prefer less holes being drilled via our 1” hole delivery method.

5) PERMANENT SOLUTION with a potential caveat

Foam will provide a permanent solution just like our limestone grout if there is no further ground erosion or compaction. However, we have seen foam adhere/glue itself to the slab and /or adjoining foundation that make any additional lifting potentially impossible without causing damage to the slab or foundation.


Video evidence of a local project we fixed that previously used poly-foam

You can see the tunnels created by the ants throughout the foam.  If enough of this material is either devoured or removed by any unwanted tenants, the slab will be at risk for eventual collapse.

Why Now? What’s the Back-story?

Why is PolyFoam en vogue and is it the “latest & greatest” technology? The simple answer is no. It is not a new technology. The industry has merely found a way to capitalize on selling the chemical components on a consistent basis to its franchisees or end users as a source of ongoing revenue. On the other hand, A-1 Concrete Leveling can purchase crushed limestone from a number of different sources and isn’t reliant on one single source for its material.

It is our intention to educate the consumer so that they can make the choice as to what process best suits them and their property. There are some benefits to using foam in more industrialized or commercial highway applications performed by those who have multiple years of experience and training handling these types of chemicals and their proper mix of them, but for our purposes in serving your home or business we will stay committed to using a tried and true environmentally safe material that has been successfully utilized in resolving just about every sinking concrete situation we have encountered in over 20+ years.