Minimum Slope For Concrete Slab Drainage

The standard formula for the slope of a concrete patio is a 1 4 inch drop for every foot of length.

Minimum slope for concrete slab drainage.

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. Slopes that are steeper than this are fine but you may also wish to consider the ease of mobility on a concrete patio that is too steep. The standard slope for proper concrete drainage is a one quarter inch drop for every foot of length.

The proper slope for runoff drainage is a 1 4 inch of slope per foot of concrete slab. But the reason for including any fall rather than making the surface level is to allow the concrete surface to drain. So to calculate the difference in height between one end of a patio or walkway and another simply multiply the length by one quarter. You have to consider the surrounding grades and any nearby structures of course.

When drainage is required on surfaces at facilities covered by the ada the minimum and maximum slope become the same. If the slope is more gradual than this you may run into trouble getting water to run off properly. 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. If physical barriers such as walls slopes or the lot lines limit the ability to achieve 6 inches of slope within 10 feet of the foundation than drainage can be achieved by installing drains or swales.

If the slab elevation at the trench. Section r401 3 impervious surfaces that are within 10 feet of the building s foundation must slope at least 2 away from the foundation. This means the end of a patio protruding 10 feet from a home will drop two and a half inches from the. 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.

Walk in any direction on a patio slab 1 48 1 4 in ft would also appear to be the maximum allowable slope for the slab in question which presents a dilemma. A 2 slope will probably ensure better drainage we could also find no slope tolerance for use when a floor slope is specified. What is a good rule of thumb for the fall or slope on exterior flatwork. If providing adequate drainage is a problem because of other building structures surrounding the concrete slab you may wish to consider the addition of a drain on.

I ve heard both 1 8 inch per foot and 1 4 inch per foot. Proper drainage slope based on the international residential code is a minimum fall slope of 6 away from the foundation for the 1st 10.