Slope For Concrete Slab Drainage

The proper slope for runoff drainage is a 1 4 inch of slope per foot of concrete slab.

Slope for concrete slab drainage.

The standard slope for proper concrete drainage is a one quarter inch drop for every foot of length. A concrete slab that is 10 feet long should have a slope away from the home of 2 1 2 inches. Positive drainage requires a slope of 1 4 in ft 20 mm m however even at this slope some standing water often called birdbaths should be expected after a rain due to construction tolerances and normal surface deformations over time. A 2 slope will probably ensure better drainage we could also find no slope tolerance for use when a floor slope is specified.

So to calculate the difference in height between one end of a patio or walkway and another simply multiply the length by one quarter. Slope the sand 1 inch for every 20 feet. Pour the sand into the trench sloping it toward the area you want the water to drain to don t drain it toward the house. Aci 117 90 standard specifications for tolerances for concrete construction and materials gives a level alignment tolerance of 3 4 inch for top of slab elevation of slabs on grade.

Set forms so that the concrete slab surface slopes a minimum of two percent or 1 4 inch per foot to provide adequate drainage. Generally using 1 8 inch fall which is 1 1 4 inch per 10 feet works well on larger surfaces like driveways and patios but it requires good screed bullfloat and finishing operations to minimize water puddling birdbaths. Use a scratch template typically a piece of 2 by 4 or 2 by 6 lumber equal to the specified slab thickness with stakes attached to the top surface at each end or a string line across the top of the forms to ensure proper slab thickness. The recommended slope is 1 4 inch per foot but it can be anywhere from 1 8 inch to 3 8 inch per foot depending on other factors.

The patio needs to have a uniform surface to lay on. You need to remove any vegetation soft soil and rocks before you begin. If the slab elevation at the trench drain is within 3 4 inch of the plan elevation and the slab top elevation farthest from the drain is also within 3 4 inch of plan elevation the slab. Calculate the ideal slope the standard formula for the slope of a concrete patio is a 1 4 inch drop for every foot of length.