Grade beams are used in footing construction when a full footing is not needed, but spot footings are inadequate to the task of distributing the load carried by the foundation piers. Grade beams are a kind of rebar column structure (evenly spaced bands with continuous bars) that are laid horizontally in trenches or forms beneath the foundation piers. You pour grade beams much in the same way that you would pour any type of concrete; however, there are some unique considerations to keep in mind.
Pour at one end of the concrete beam. Aim the concrete chute from the truck (or the end of the hose from the pump) and release the concrete. Do not move the chute or hose forward until the area of the form below it is filled with slightly more concrete then you actually need to reach the finished height of the grade beam.
Vibrate the concrete thoroughly. For every 6 feet of pouring, "hit" the concrete with the vibrator. Hitting the concrete means to insert the vibrator fully into the concrete in several places. When the concrete is vibrated, the level of the concrete will fall. Add more concrete if it goes below the height that you need for the finished grade beam. Vibrating concrete gets rid of any air pockets and makes sure that the concrete works its way fully around the rebar in the form.
Complete pouring to the concrete height needed in the grade beam. Grade beams do not need a trowel finish. You can roughly level and finish the beam using a small piece of 2x4 cut to slightly less than the width of the beam. Move the 2x4 in a back-and-forth motion across the surface of the concrete to level it off, do this the entire length of the beam.
Things You Will Need
- Concrete vibrator
- Chalk line (if needed)
- Nails (if needed)
- Spray paint (if needed)
- If you have to hold the pour to allow for an upper rebar structure (like a slab) to tie into the grade beam, then mark the height you need to pour the beam. The height is called the "grade" of the concrete. If your beam is inside a wood form, mark the grade with a chalk line or nails placed in the form every 4 feet. If your beam is in an earthen trench, then mark the height with spray paint.
- Make sure you are pouring the right mix of concrete into your grade beam. Typically, the mix for a grade beam is much different than the mix for a slab, and what is required will be written on your building plans. If you use a mix that is not designed for the kind of deep load bearing that a grade beam is subjected to, the beam may crack and break, and cause damage to the upper structure.