How Do You Pour Concrete Under Old Foundation?
Old foundations can become weakened by air or water getting underneath them and over time eroding either the soil supporting the foundation or the concrete itself. You may be able to see such a pocket at the base of the foundation, or if you tap on the foundation or slab you may hear a hollow sound. You will need to pour concrete under the old foundation in order to rebuild its structural integrity. This is a process requiring care. Locate the areas with gaps underneath the old foundation. This may be as simple as finding where, along the sides, you can see the bottom of the foundation or see underneath it. You may have to use a hammer to tap the top surface of the foundation to locate hollow points. Flag areas that are close to the edge of the foundation with survey stakes. Dig underneath the foundation until you locate the open pocket. If your hollow pocket was found by tapping on the foundation’s surface, use a hammer drill to drill out the concrete until you have accessed the space
