Slope For Concrete Slab Drainage

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.

Slope for concrete slab drainage.

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. But the reason for including any fall rather than making the surface level is to allow the concrete surface to drain. The only aci document that discusses slope of exterior patio slabs is aci 302 1r 04 1it states that. 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.

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. If the slope is more gradual than this you may run into trouble getting water to run off properly. 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. A 2 slope will probably ensure better drainage we could also find no slope tolerance for use when a floor slope is specified.

Set forms so that the concrete slab surface slopes a minimum of two percent or 1 4 inch per foot to provide adequate drainage. A concrete slab that is 10 feet long should have a slope away from the home of 2 1 2 inches. The standard slope for proper concrete drainage is a one quarter inch drop for every foot of length. Slope the sand 1 inch for every 20 feet.

The patio needs to have a uniform surface to lay on. So to calculate the difference in height between one end of a patio or walkway and another simply multiply the length by one quarter. 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. You need to remove any vegetation soft soil and rocks before you begin.