Stabilizing a Sinking Fire Station in Franklin, Ohio

Challenge

Back in 2023, we were at this Fire Station to stabilize the foundation for the living quarters and the rest of the station excluding the garage. You see, the slab foundation supporting the living quarters was sinking into unstable soil. The sinking slab was causing all the finished flooring in the living quarters to crack and break, resulting in a huge nuisance for the Firefighters. They wanted the slabs to stop sinking any further so they could redo all their floors without having to worry about their living quarters being damaged again. Firefighters also know a lot about structures, so they were quick to catch onto the problem before most, and they were highly interested in our processes. We injected our PolyLevel foam underneath the slabs to stabilize the living quarters so the Firefighters wouldn't have to worry about their finishing products being destroyed for a second time. Our PolyLevel foam system is relatively easy, as we first drill tiny pea-sized holes through the sinking concrete, and then we inject these holes with our foam. The foam then expands thanks to its chemical composition, reaching all the hard to reach gaps between the slab and the sunken soil. 

Happy with us and our PolyLevel process from the first time around, the fire station called us again for a new problem. Similar to the first time, the garage was separating from the rest of the fire station, creating cracks in the slab floor. Obviously, gaps in the garage floor are quite concerning for our beloved Firefighters, as they have to be able to quickly run to and from the garage when called to duty. If they waited to get this problem fixed, far worse cracking could appear in their floor. You see, the garage was built on a heavy slab foundation, as thick concrete slabs were used to be able to support the weight of all the firetrucks and their equipment. These slabs are around a foot thick, and are coated in an epoxy to help keep the Firefighters from slipping and to prevent chemicals and other liquids out of the floor. We weren't going to be able to use our PolyLevel method like we did in 2023, as the garage slab was far too thick and heavy, (especially with all the trucks) to be able to properly stabilize it with just foam. This time, we were going to have to use a different repair process. 

Solution

This time, our Inspector drew up a plan for our pier underpinning process, (piers are also known as piles). Our steel pier underpinning process is similar to our PolyLevel foam method, in that we want to address the real problem: The sinking dirt the foundation rests on. Our plan consisted of 11 piers, all in the problematic area of the garage with all the cracking. This area is where the garage connects to the living quarters, and was on a seperate foundational slab than the living quarters. Usually, we are able to install our piers around the outside of a structure by digging through soil around the foundation. However, because this problem area was where the two seperate foundations met, we were going to have to dig up the concrete floor to be able to expose the footer.

You see, we want to be able to expose the footer to be able to properly attach our piers to the footer. A footer is the bottom most part of a foundation, designed to dissipate the weight of the structure against the soil. Our whole goal with pier underpinning is to be able to help the footers out by further dissipating the weight into load-bearing soil, (load-bearing soil is deep into the ground, where the soil is most compact).

After we dug the concrete floor to expose the footer, we then began to drive the steel piles down into the ground with a hand-held tool through the trenches we dug. Their screw like shape allows them to be easily driven into deep depths. After we screw them all down, we then attach the ends of them to a bracket. We then attach the bracket to the footer, where we are able to get a solid connection thanks to the brackets "L" shape that hooks underneath the rectangle footing. In some cases, after the brackets are attached, we are able to lift the footers with hydraulics. We didn't have to in this case, as the sinking was caught early on and there was no need to try and lift the foundation. After we installed the helical piles, we then covered up the trenches where they were drilled with some fresh concrete. 

With their foundation stabilized, all the firefighters had to do was wait for the concrete to cure, then re-epoxy if they please. No longer will they have to worry about their station sinking.