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I’m planning a two car carport with a concrete slab for a parking surface next to my house. The soil is heavy clay but the location is slightly elevated so the surface drains well. I would like to support the carport on piers below frost line and pour the concrete in between. The area slopes away from the house approximately 6 inches over a distance of 20 feet. I would like at least a 4 inch slab. The common approach would probably be to excavate so the slab is below grade at the house end. However, I’m reluctant to dig too much because our heavy clay soil drains poorly. I’m afraid if I create a low spot, water will tend to collect under the slab. I’m thinking of adding a layer of gravel that tapers from zero at the house to about six inches at the outer edge. I’d lay the concrete on this base with the outer edge “turned down” to form a 10 inch thick grade beam to contain the gravel and provide some edge strength. At some point in the future, I may decide to enclose the carport, so I’d want the slab surface fairly level to simplify framing. Any problems with this type of approach ?
Thanks
Dan
Replies
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I'm planning a two car carport with a concrete slab for a parking surface next to my house. The soil is heavy clay but the location is slightly elevated so the surface drains well. I would like to support the carport on piers below frost line and pour the concrete in between. The area slopes away from the house approximately 6 inches over a distance of 20 feet. I would like at least a 4 inch slab. The common approach would probably be to excavate so the slab is below grade at the house end. However, I'm reluctant to dig too much because our heavy clay soil drains poorly. I'm afraid if I create a low spot, water will tend to collect under the slab. I'm thinking of adding a layer of gravel that tapers from zero at the house to about six inches at the outer edge. I'd lay the concrete on this base with the outer edge "turned down" to form a 10 inch thick grade beam to contain the gravel and provide some edge strength. At some point in the future, I may decide to enclose the carport, so I'd want the slab surface fairly level to simplify framing. Any problems with this type of approach ?
Thanks
Dan