Slope For Concrete Slab Drainage

If the slope is more gradual than this you may run into trouble getting water to run off properly.

Slope for concrete slab drainage. 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. Slope the sand 1 inch for every 20 feet. You need to remove any vegetation soft soil and rocks before you begin. 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 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. 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. 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.

So to calculate the difference in height between one end of a patio or walkway and another simply multiply the length by one quarter. 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. 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.

A concrete slab that is 10 feet long should have a slope away from the home of 2 1 2 inches. The patio needs to have a uniform surface to lay on. 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 standard slope for proper concrete drainage is a one quarter inch drop for every foot of length.