A slab foundation is a thick, large slab of concrete that is usually 4 or 6 inches thick. The concrete is usually poured all at once in order to achieve uniformity in the mix and maximum strength. Slabs and foundations are used to level and bear the load of small items such as an Air Conditioning unit, something a bit larger like an RV resting on a concrete pad, or for a large structure such as a home, garage, or shed.
Importance Of a Strong Foundation for your Foundation Or Concrete Slab
Usually, the slab concrete foundation is constructed on the property or building that has been graded. The soil must be graded properly because the soil is acting as the foundation for your concrete slab or your foundation (confused yet?). If the soil is not properly graded and compacted, once loading is applied on the slab, the concrete might settle or sink due to the poor compaction and grading of the soil underneath. For smaller and medium size pads, you can use a compactor such as a sheepsfoot compactor. For larger foundations, it is more efficient to use a vibrating compaction roller.
How To Form The Area For The Foundation Or Slab
Make a form by using 2” by 4” or 2” by 6” boards. If you’re doing a larger foundation, you’ll need special boards used for foundation pouring. A premade form can also be used but are relatively expensive, best to go with boards. A pro tip: Spray the side of the board that will be touching the concrete with WD-40, motor oil, or even olive oil. That will make it a lot easier to remove the form from the concrete after the slab has hardened. Once the boards are in place, they have to be reinforced with stakes so they don’t collapse to the weight of the concrete.
Level the ground within the form: Regular rakes and shovels can be used to level the ground completely within the frame. Use a laser level to ensure the flatness of the ground, as well as to slope the ground for drainage.
How to Reinforce the Slab and Foundation
There is various supporting rebar that is used for garage floor slabs, RV pads, or backyard slabs. You can use either a #3, #4, or #8 rebar. The number represents the amount of 1/8s of the rebar, i.e. #3 is 3/8, #4 is 4/8s or ½, and #8 is 1”. Spacing is also important. You can place your rebar 12” on center, or 16” on center, then you can start creating your grid. For structure foundations, post tension cables are often used whereas others are reinforced with thicker rebar. It is important to understand the properties of the underlying soil. Consider getting a geotechnical engineer to bore a few samples from the ground so that he can make recommendations to a structural engineer for a foundation design. This will ensure your foundation has enough load-bearing capability of the building structure and make it safe and sturdy.
How To Achieve Positive Drainage When Pouring A Slab
The slab should be sloped 1/8-inch per foot to eliminate the standing water and slope away from the existing structure. If the concrete foundation is wedged between two structures and bans proper drainage, then install a drain that will collect the water in the concrete at a low point and divert it away. Drainage is also an important reason for the soil underneath to be compacted well. If not, your concrete pad will most likely settle and create a basin where the water can start pooling.
How Long to Let the Concrete Cure
The final step of this process is concrete curing. Concrete curing takes about 28-days. It should be done soon after the finishing is completed. There are various methods of curing, such as wet curing blankets, concrete with plastic sheets, application of liquid membrane-forming curing compound, and continuous sprinkling. One note to make, if you’re pouring a slab or foundation where a portion of it is in a shadow area from a tree or an adjacent building for example, make sure to sprinkle a curing agent which will allow that area to cure and dry uniformly with the rest.
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