Choosing the Right Size and Type of Gravel for Your French Drain

A French drain is a fantastic solution for keeping your yard free from excess moisture. It effectively draws water away from certain areas, like near your house foundation, in order to prevent any damage to the structure. However, when it comes to choosing the right gravel for your French drain, you need to consider various factors, such as the slope of your yard and whether you plan to use a perforated pipe. Let’s explore the best options for your French drain.

Crushed stone

French Drain Basics

A French drain consists of a sloped ditch or trench that redirects water away from the problem area. The slope typically ranges from 1 to 2 percent, with the high point located at the spot needing drainage. To construct the drain, you’ll need a layer of gravel at the bottom of the trench, topped with several inches of coarse sand. Some French drains even have sod or a drain pipe to enhance their efficiency and durability.

Basic Gravel Bottom

The gravel used for the bottom layer of your French drain serves as a pathway for water flow. If you’re using a perforated pipe, the gravel should fill one-third of the trench’s depth. Otherwise, it should fill two-thirds. You’ll want to choose gravel that is between 1/2 inch and 1 inch in size. Larger gravel allows for better water flow and decreases the likelihood of clogs and blockages. If you don’t plan to use a perforated pipe, opt for even larger gravel, such as 1 1/2 inches in size. Avoid smaller gravel like pea gravel, as it won’t allow sufficient water flow. Additionally, always opt for washed varieties of gravel or stone to prevent fine dust and particles from hindering water flow.

Hard Rock Rules

When it comes to longevity, hard rocks like granite or river gravel are excellent choices for French drains. Unlike other rock varieties, such as sandstone or limestone, hard rocks won’t break down as much over time. River gravel, in particular, has undergone significant erosion, making it an ideal option. It is sourced from dried river beds, thoroughly cleaned, and then sold to the public.

Top Layers

For the top several inches of your French drain, coarse sand is the perfect filler, regardless of whether you’re using a perforated pipe or not. Coarse sand doesn’t clump or clog and has been washed to remove any impurities. If you’d like to camouflage the drain, you can layer sod on top of the sand, making it less noticeable. Alternatively, you can place a weed barrier cloth over the sand layer and add decorative large rocks for a more aesthetically pleasing look. Using rocks on top also ensures easy access to the drain, allowing you to check its functionality whenever necessary.

By considering the slope of your yard and making the right choices for gravel and sand, you’ll create an effective French drain that keeps excess moisture at bay. Remember to use washed varieties of gravel and adhere to the recommended sizes for optimal water flow. With the right materials in place, your French drain will serve you well for years to come.