What is a Grade Beam?
In construction, a grade beam is a type of foundation system used to distribute the weight of a building over unstable soil. The beam may sit directly on the loose soil or be supported by pipe pilings that extend deep underground. Builders then position a series of piers or foundations wall on top of the beam to support specific building components.
These foundation systems consist of heavy-duty concrete beams that are often reinforced with rebar or steel mesh for additional strength. Unlike standard spread footers, grade beams are designed to minimize deflection instead of simply transferring loads directly to the ground below. This allows the beam to span loose or unstable areas of soil, and redistribute building loads to areas where soil is more compact.
Civil or geotechnical engineers can design a grade beam foundation based on local building codes and the specific demands of the project. As part of the design process, the engineer will take soil samples and examine site conditions to find the most stable areas. He will then specify the depth, width, and materials for the beam to maximize safety and ensure the building loads receive adequate support.
Effective construction of this type reduces the risk that the building will sink or settle over time. By minimizing movement, these foundation systems lower maintenance requirements and reduce structural damage. An adequately-supported building also provides better safety for occupants, particularly in areas where soil conditions are poor. Earthquake-prone regions may have even more stringent requirements regarding the use and construction of these beams to support and stabilize a building.
This heavy-duty beam foundation system serves as an alternative to more basic footer designs. Spot footers, which are typically placed below a column or other bearing point, work best in fairly stable soil. Spread footers, which support perimeter walls and other heavy-duty components, are often associated with more deflection and less strength.
Grade beams may be used around the entire building perimeter or just at specific areas. If one part of the soil is unstable, the beams can redistribute weight in just that section. When poor soil conditions are found throughout the site, they may support all exterior walls, columns, and even items like staircases. In some industrial applications, grade beams may be required to support extremely heavy equipment, even when soil is relatively stable. Many types of medical and manufacturing equipment also require the added stability provided by this type of foundation.
@parklinkz – No, I don’t think your cousin’s house will be going anywhere! I’m glad her contractor had the foresight to take those precautions. It isn’t pretty when a house’s foundation shifts.
If you pick up a ragdoll, hold it by its middle, and then tilt at an angle, you can get an idea of what a house looks like when suffering from foundation settling. The doorways and windows get tilted. The doors won’t open, and the windows won’t close. In severe cases, the walls start falling away from each other like pages of an open book.
I work with a company that fixes houses that have settlement issues. Often, the only way to fix the problem is to lift the affected house up off the ground and drive piling beneath the foundation. That stabilizes the soil and prevents future settling.
@ginSoul – Soil settling can be a big problem for buildings near coastlines. My cousin is building a house right on the beach – on top of the shifting sand. Her house is in danger of being lifted up out of the ground in a couple of decades, so her contractor is pulling out all the stops.
Her foundation has concrete pilings driven 90 feet into the ground. Each piling is bolted to her house’s grade beams, which are reinforced with steel beams. The entire beach could blow away and her house probably wouldn’t move an inch. It’s amazing.
I live on the coast, and every few weeks, I’ll hear the sound of a pile driver pounding something into the ground. It goes on for hours, and I’ve always wondered what it was doing.
Then, I kept hearing that soil settlement is a big problem for homeowners here. This entire town is built on top of marshes and the land is pretty wet. I guess all that moisture makes the soil unsteady.
So now I know what all that pile driving is about! It must be construction crews driving pillars into the earth to create support for concrete grade beams and the foundations of new buildings.
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