Concrete grade beams are construction elements utilized in residential and commercial construction. Grade beams can be utilized with footings to support elements like building walls, load bearing walls, columns, building frames, etc. These are essential concrete elements that have a very important role in the support of building structures.
With formwork, reinforcement, and pouring of grade beams, attention to detail and project schedule are critical. When looking at building a building in general, these serve as what is know as predecessors to other tasks in a construction project, like building walls, creating stairwells, doing steel structures etc. Grade beams with concrete slabs are basic structural components of most homes and buildings.
Concrete Grade Beam Schedules
On larger buildings, with complex concrete structural requirements, grade beam schedules are typically provided to outline the construction requirements and installation instructions for various types of grade beams.
A concrete grade beam schedule will provide details on: width, height, reinforcement, and sometimes elevations.
As grade beams are constructed as ‘beams’ hence, the name, grade beams, top and bottom rebars in addition to stirrups/ties are noted in a grade beam schedule for reinforcement. Typical spacing of stirrups to coincide with the top and bottom rebar are provided for the rebar details too!
This type of information is provided to rebar detailing and supply companies for finalization of reinforcement orders and installation instructions for rebar tying/install crews.
Typically in Alberta standard or carbon steel rebar / black bar is fine for pile caps because concrete cover offers enough protection against corrosion.
How Grade Beams are Poured
Concrete grade beams are generally poured as the first portion of a building built on grade, or coincide with other items like piles/foundation walls etc.
With items like foundation walls, pile caps, pilasters, and other foundational concrete elements, concrete grade beams make the basis for residential and commercial building SOG construction. With slab-on-grade construction, concrete slabs are poured to the grade beam, adjoining the grade beam, but generally not poured into the grade beam. This means the grade beam is poured first before the slab. Each concrete element is poured separately.
Concrete grade beams may use void form or forms to separate the bottom of the concrete from the subsoils or crushed gravel underneath.
Concrete Grade Beam Adjustments
There may be depressions in concrete grade beams to facilitate installation of items like overhead doors, doors, ramps etc.
The concrete grade beam is a great way to identify the layout of a building, because it is typically the perimeter of the building. There may be architectural building overhangs above the location of the grade beams, but in general, you will find that a grade beam aligns with the grid-lines of the building. This is unless a slab-on-grade construction is used elsewhere.
A concrete grade beam works to provide stable foundation for slab on grade structures but can also be used to expand the building footprint of buildings with deep foundations, foundation walls, pilasters, pile caps etc.
Top of grade beam elevation is essential to maintain and use for concrete construction layout of the form-work and reinforcement. Top of grade beam elevation may coincide directly with the top of slab elevation on most projects, so the concrete contractor has to meet the T.O. GB elevation as best they can to avoid costly rework.
Concrete Grade Beam Reinforcement
Grade beam reinforcement is typically of cage rebar, as in 4 sided rebars, placed at intervals along the length of the grade beam. These provide structural reinforcement which is alike other concrete elements, that use vertical & horizontal rebars.
The cages are specially brought in for these grade beams. Skilled placement of rebar, and inspection of rebar, along with form-work installation is key to ensuring the correct width, concrete covers, and coordination between the reinforcement and the form-work.
Concrete reinforcement means and methods are generally dictated by structural drawings on most projects. Larger projects have complex sets of structural concrete drawings, but for smaller projects, the concrete contractor may be able to dictate probable reinforcement for the grade beams.
Concrete grade beam reinforcement could best be described akin to concrete beam(for multi-level structures) rebar reinforcement.
Air Entrainment in Concrete Grade-Beams
Grade beam concrete is frequently provided air entrainment mixtures, that protect against the measures of cracking/splitting. They allow water to enter the concrete due to water logged soils, or hydro-static pressures, and with this migration of water, concrete has less chance of cracking/breaking with freeze-thaw cycles because expansion pressure is dissipated by water leaving the concrete.
Air entrainment in concrete in grade-beams is not problematic for the finish of the concrete because there is not supposed to be any exposed grade beam in the interior of the building other than under supporting wall elements, columns, and other concrete elements.
If air entrainment concrete is utilized for interior concrete, then the slab-finish will difficult to achieve.
Concrete grade beams can also tie in with adjoining structures like patio slab-on-grade structures. These patio slab-on-grade structures can be doweled into the concrete foundation/grade-beam.
Grade-beam Alternate Uses
Grade-beams are also used in supporting concrete ramps where needed, for vehicular access, providing a basis for the ramp slab to be poured and outlining the structure in itself.
Grade beams are essential to distribute the load of the building along the perimeter of the building. In some cases the grade beams will be placed in through the building interior to further support the structure above. Other use cases for grade beams involve shorter pile to pile beams that are used as supports for structures like stairs or elevator shafts in the interior of the buildings.
This means grade beam placement and pouring can be both continuous or non-continuous depending on structural requirements. In addition, concrete grade beam depth and dimensions can vary dramatically to suite the load requirements of the building. Increases in beam width/height are typical with projects too. Variations in beam depth for perimeter grade beams, or for interior grade beams are typical, as dictated by the structural engineer, throughout a project.
Conclusion
Concrete grade beams can be utilized in a variety of means and methods in architectural and structural requirements dictated by the plans set forth for the building. They are essential in slab on grade construction, working in conjunction with elements like foundation walls, pile caps, pilasters, piers and more in other projects to create the structural supports for the entire project.
Grade beams are typical in almost every residential and commercial concrete project that has slab-on-grade construction with serious design considerations (loads).
If you are a homeowner or property manager, understanding what a grade beam is can be difficult… but trust the services of a professional concrete contractor! They are there to guide you through the process of what’s needed in your building and what is not, making sure you are getting your building/home built correctly.
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