Let’s All Say it Together….Mud Jacking. It’s Super Fun.
Mud jacking is a procedure done to foundation floors or any concrete slab on grade where the underside of the slab is filled with concrete or a slurry to raise the existing concrete if it has changed elevation and sunk. This article will explain how it relates to the plumbing field and why it can be difficult but necessary.
When involved in new construction, rehab or service work the way a labor contractor backfills the area of work or foundation is extremely important. It is the reason why many municipalities choose to inspect the foundation or open slab before the foundation is poured or before the slab is repaired.
Most people that have been involved in building a new home or have seen one built can attest to seeing the foundation walls being backfilled with the site spoils. If the material under the floor or against the side of a foundation are not backfilled properly you run the very real risk of the ground settling. All ground settles but if the proper steps are taken the settled ground will rarely have adverse affects under reasonable conditions.
That brings us to a scenario where mud jacking is necessary. Let us reiterate, ground can settle in a building that has been meticulously backfilled but a good percentage of the time improper backfill is the cause for the ground sinking. We received a call from a customer telling us that his waste piping had come apart right under his floor in his laundry room immediately in front of his garage. We dispatched a service tech to inspect the site and verify the homeowners observation.
Upon arrival the plumbing technician did see that the piping had come apart under the slab in the laundry room, the real question is why? We asked the home owner if we could make a small hole in the wall to insert a Ridgid Mini Sea Snake (small color LCD fiber optic camera) to see inside the wall and possibly get a diagnoses. He agreed and when we inserted the camera we saw quite a bit more than we expected. The floor had pulled away from the underside of the slab in the laundry room and under the garage floor.
Upon further inspection we saw that the ground had fallen in a significant portion of the laundry room and part of the garage and the waste piping servicing the laundry room was undersized and completely exposed. Because a permit had to be taken with the municipality the plumbing inspector wanted the piping to be properly sized upon replacement.
Back to mud jacking.
How do we sawcut or break-up the concrete without running the risk of the concrete falling? In some spots the ground had fallen 3ft from the underside of the concrete slab so you can imagine this could be dangerous. Another issue that arises is when you make the plumbing repairs and backfill the void how do you make sure the backfill is evenly distributed to avoid the same issues and minimize the risk of the replaced concrete sinking.
A mud jacking professional suggested they bore small holes in the concrete slab and inject a slurry under the slab to bring the ground up to the bottom of the slab. This slurry would fill the cavity below the concrete and support the slab so we could safely cut the concrete. However there was a problem, the slurry used for the mud jacking could enter the open sewer lines.
We isolated the broken line from the active sewer by inserting an inflatable test ball through a clean out which prevented the slurry from entering the sewer. The plan was to have the experts mud jack under the laundry room and garage, let the slurry cure, sawcut the area where the pipe was to be repaired/replaced, dig down to the defective piping and repair and backfill using the code approved materials and method.
Obviously if no plumbing was being repaired or replaced the mud jacking would be done with a concrete slurry so it would harden into a stable base while filling all of the voids under the slab.