In this video AeroFoam will be filling the void under a concrete slab in Parachute, Colorado by pumping polyurethane foam underneath. Below is a picture generally representing this. Concrete sinks if the supporting soil is weak or prone to compression. Where our concrete patio meets the foundation under the sunroom we have a big hole that has opened up (about the size of a golf ball) that you can see in the center of the photo: And up close: We've lived in the house for 4 years and this is the first time this has happened. It will led to cracks in the surrounding asphalt. Flowable Fill . Work the patching material into the crack or hole with a trowel. I once saw a home improvement show on the DIY Network where they raised sagging slabs by core drilling the slab & injected "flowable fill" concrete into the hole in the slab until the slab came back up to grade. I had filled the hole with dirt last year. 1. Is expanding foam the best thing to use for this and how easy is this to apply? The HoleMole 3-Step Process. Erosion under concrete is serious, whether it’s your foundation, driveway, patio or sidewalk that’s affected. If you have difficulty ramming the 2×4, use a sledge hammer to hit the end of the 2×4 board. The best way to fill a gap in a driveway depends heavily on what kind of material your driveway is made from. There was a 4" PVC pipe running up from the ground where the old drain was attached. 5 5 Answers from MyBuilder Handymen. how to fill a void under a concrete slab. Pour the concrete into the hole using one of three methods. Part 3 of 3: Filling the Sinkhole. northview property mainenance. Get tips on cutting out that area of the driveway, repacking the void with soil, and then restoring the driveway. We have a concrete front stoop. The house was built in 1997, we bought it last summer.  Share. Place the concrete from the other side, using some wood or something to push/pump the concrete to the side with the plywood. The VB always goes against the concrete slab. Using expanding foam to fill a hole. Mold needs a medium to grow on, so unless the mold is on the back of the sheetrock or on wood, its not mold. Fill in holes and cracks less than 1/4 inch with silicone caulk and a caulking gun from the outside. It’s imperative to fix erosion under concrete as soon as possible, but first you need to know what to look for. Pour more patching concrete to completely fill the hole or crack. Not really sure how the void developed but the opening to it is as big as your foot, and it's size I would guess in the one cubic yard range. You can repair a concrete floor by cleaning and straightening the damaged area, and then filling it with mortar. Improve this answer. If you use a material like gravel, sand, or dirt to fill the hole in, every time it rains, water will run into your holes, fill in the voids of your material, stand in there, and accelerate rot. If the water is static or only has a light current, open the Quikrete bag, hold the opening closed, lower the bag into the water and release the concrete just above the hole. How to fill large void under concrete slab? Three steps, small porch, all one piece. Go around the perimeter of the foundation, finding your matches or toothpicks. I have small holes in a number of different parts of my house, which I think the mice are getting in and out of. Typically, the utility pipe or other equipment in the trench is first covered with an aggregate material, then the flowable fill is placed in the trench directly from the truck, just like regular concrete. Lowering moisture content is key. Backfill can also be done using flowable fill, a cementitious material with a low water-cement ratio that is delivered to the job site by a ready-mix truck. If you decide to remove the carpet, you must also pry up the tack strips, which are held in place with nails. Mix additional bucket-sized batches as needed. The change in the way I do my fences was actually taught to me by Norm from This Old House and I would never use concrete again unless the soil required it. If there is a current, you have two options.