Slab foundations are created by pouring concrete over reinforcing steel rods, also known as rebar, or by using post-tension cables after the concrete is poured; this allows for thinner slabs to be strong and sturdy. Around the perimeter of the foundation, concrete is poured in a much thicker quantity to protect the vulnerable edge, while also compensating for the added pressure of exterior walls. Proper soil grading is essential before slab foundations are built, otherwise the foundation is susceptible to shifting, sinking, and settling where soil is not properly compacted. This imbalance causes excess pressure and cracks can form as a result. In order to repair slab foundation issues, a process known as foundation leveling
can be utilized which restores the house to as close to level as possible.