Slope For Concrete Slab Drainage

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.

Slope for concrete slab drainage.

So to calculate the difference in height between one end of a patio or walkway and another simply multiply the length by one quarter. 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. The only aci document that discusses slope of exterior patio slabs is aci 302 1r 04 1it states that. 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.

The patio needs to have a uniform surface to lay on. A 2 slope will probably ensure better drainage we could also find no slope tolerance for use when a floor slope is specified. The standard slope for proper concrete drainage is a one quarter inch drop for every foot of length. 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. 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. If the slope is more gradual than this you may run into trouble getting water to run off properly. A concrete slab that is 10 feet long should have a slope away from the home of 2 1 2 inches.

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 proper slope for runoff drainage is a 1 4 inch of slope per foot of concrete slab. Set forms so that the concrete slab surface slopes a minimum of two percent or 1 4 inch per foot to provide adequate drainage. Slope the sand 1 inch for every 20 feet.