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Title of Question:

How do I prepare the ground for a concrete slab?


Name: Amy  City:

Question: What do I need to do to prepare the ground for a concrete slab? Does the grass and topsoil need to be dug out before putting down the base of stone? How thick should the base of stone be? How thick should the layer of concrete be??


Name: homebild | Date: November 1, 2004, 14:28
Answer: Answer depends for what you will use the slab. In every case, all vegetation needs to be removed, the soil graded and several inches of crushed stone added for drainage. For slabs under living spaces, codes require both a thermal barrier placed directly over the stone in the form of rigid foam insulation and on top of the foam, a layer of 6mil polyethylene sheeting to act as a vapor barrier. Garage floors need neither but it is still a good practice to place foam and plastic under garage slabs if future conversion to living space is a possibility. The thickness of the slab and how it should be reinforced and what concrete mix depends upon the use. 6" minimum fibered 3500 psi mix is common for driveways and garage floors. 4" 2500lb psi mix for sidewalks, basement floors, and patios... Slabs as foundations can vary in thickness and reinforcement based on local geology. Your local building codes will specify what you need and how local soil conditions can affect the slab.


Name: doug murphrey | Date: January 14, 2005, 15:09
Answer: How do I prepare the ground for a concrete slab?