How big should a rain garden be to handle my roof runoff?

A rain garden should be approximately 20–30% of the impervious area draining to it. For a 1,000-square-foot roof section, plan for a rain garden of 200 to 300 square feet. Increase the size toward 30% or more if you have clay soils with slow infiltration rates.

How long should water stand in a rain garden after it rains?

A properly functioning rain garden should drain completely within 24 to 48 hours after a storm. If water stands for more than 72 hours, the garden may be undersized, the soil media may be compacted, or the native soil beneath may have insufficient infiltration capacity.

Can I build a rain garden in clay soil?

Yes, but you'll likely need to install a perforated underdrain pipe at the bottom of the rain garden connected to a storm drain or daylight outlet. Without an underdrain, clay soils (Hydrologic Soil Group D) drain too slowly for a standard rain garden to function properly.

How far should a rain garden be from my house foundation?

A rain garden should be located at least 10 feet from any building foundation, and it should be positioned downslope so that water flows away from the structure, not toward it. Placing a rain garden too close to a foundation can worsen water intrusion problems.

Do rain gardens attract mosquitoes?

A properly designed rain garden does not attract mosquitoes because it drains within 24 to 48 hours—mosquito larvae require 7 to 10 days of standing water to develop. If your rain garden holds water for more than 72 hours, it needs design corrections to improve drainage.

Will a rain garden fix my wet basement?

A rain garden alone will not fix a wet basement. Basement water intrusion is typically caused by improper grading, failed footing drains, or hydrostatic pressure from a high water table. These issues require direct solutions like regrading, waterproofing, and subsurface drainage. A rain garden can be part of a broader strategy by managing downspout runoff away from the foundation.

Rain Gardens: Do They Actually Solve Drainage Problems?

Do rain gardens really fix yard drainage issues? Learn how rain gardens work, their real capacity limits, when they help, and when you need a different…

By Low Point Labs

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