Grade beam
A reinforced concrete beam at or near ground level that spans between piers or footings, carrying wall loads across weak or variable soil.
What does grade beam mean?
Grade beams are used where the soil directly under a wall cannot be relied on, transferring load to deeper supports such as drilled piers or piles. They are designed as bending members, so their reinforcement is substantially heavier than a spread footing's. They also appear in post-tensioned foundation systems as stiffening ribs.
In practice
On expansive clay or steep sites, the foundation is often piers plus grade beams rather than continuous footings.