Minimum Slope Of Concrete Floors For Water Drainage

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.

Minimum slope of concrete floors for water drainage.

Typically on straight road sections the drainage gradient is at least 1 3 due to the normal cross slope of 1 3. 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. You need 1 4 inch of slope for every linear feet of floor space. 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 standard formula for the slope of a concrete patio is a 1 4 inch drop for every foot of length. For example a floor that extends 4 feet away from the drain should have 1 inch of overall slope. The only aci document that discusses slope of exterior patio slabs is aci 302 1r 04 1 it states that. As a rule of thumb all areas around the drain should have a similar slope.

A little more won t hurt but too much will. The recommended slope for flat roofs is usually 1 1 8 inch per foot or 2 1 4 inch per foot according to the professional handbook of building construction published by john wiley sons new york. In curved sections the drainage gradient is higher and may often reach 5 12 due to superelevated cs that may reach 5 8 in areas with icy roads and up to 12 in areas without icy roads. 4 drain pipes should be about 1 4 inch per foot.

We could find no reference to recommended slopes when trench drains are used in a floor. If the slope is more gradual than this you may run into trouble getting water to run off properly. 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. 1 8 per foot is minimum you should use.

But the reason for including any fall rather than making the surface level is to allow the concrete surface to drain. If too little slope even if the water drains it won t be self cleaning i e. The preferred slope is between one quarter and one eighth inch per running foot of floor length.