How to Slope a Concrete Patio for Drainage

When planning a concrete patio construction project, one of the most important things to keep in mind is that your patio will inevitably have water buildup during rainy and snowy periods. If that water stays on your patio surface it will cause damage to the structure of the concrete itself and may form a breeding ground for mosquitoes and mold. Thus, it is crucial that you plan on providing a method for the concrete patio to drain the excess water that collects on top. Ideally, this water should drain off of the patio and away from the foundation of your home, where it can help to water the grass or plants in a garden. Sloping your patio properly will ensure that the concrete surface has the proper drainage capacity.

Step 1 -- Gather Your Materials

The exact materials that you'll need for this project depend somewhat on your patio and the state of construction. If you haven't yet built a patio and are just considering how to account for drainage in your construction plans, you may not need to gather all of these materials. However, if you've already built a patio but have not allowed for proper drainage, or if your existing patio does not drain adequately, gather these tools and items:

• Concrete mix (the same type as your existing patio)
• Wood supports
• Tools for laying concrete (wheelbarrow, shovel, concrete knife, etc.)
• Tape measure
• Blocks and supports to ensure that the concrete levels properly

Step 2 -- Calculate the Ideal Slope

The standard formula for the slope of a concrete patio for drainage purposes is the following:

For every 1 foot of length of concrete on the patio, there should be a drop of 1/4-inch in order to account for the slope.

If the slope is more gradual than this, you may run into trouble getting water to drain off of your patio. 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. This is a matter of personal preference and is also dependent upon the shape and overall design of your concrete patio.

In order to calculate the necessary slope for your patio, measure the longest part of the patio with a tape measure. Next, multiply the number of feet in the measurement by 1/4 in order to find the number of inches in elevation that the two edges of the patio should differ by.

Step 3 -- Mix and Lay Concrete

Follow the instructions on the concrete to mix and lay the concrete on top of your existing patio, if you need to add a slope to a previously built concrete platform. You may need to use wooden supports in order to make sure that the concrete lays evenly. Set up the supports along the side of the section to be sloped and along the edge of the slop as well. Pour the concrete gradually into the mold that you've made with the supports and allow the concrete to begin to set before removing the supports. For additional assistance in laying the concrete itself, consult with an expert at a local home improvement center or related store.