Drainage Solution: How to Make a Foundation Drainage Garden

IF your basement is perpetually wet, a hit of landscaping may solve your water problem. A foundation drainage garden has dual functions of enhancing your landscape and keeping your basement dry Check the slope of the ground near your foundation walls using a level that’s set on top of a long straight 2 x 4. A minimum slope of ½” per foot is necessary for water runoff. If your slope does not meet this minimum, you’ll need to regrade and add soil until the slope is achieved. When the regrading is done and sufficient slope has been established, you can install a drainage garden over a waterproof membrane. Consisting of a waterproof underlayment covered with soil or rocks (or some combination of the two), drainage gardens have the added bonus of being virtually maintenance free. It is recommended, however, that you add plant cover for visual appeal and to prevent the soil from eroding.

When selecting a material for top-dressing the drainage garden, look for colors and textures that are native to your area and probably already exist in your yard. Mulch, bark, and other organic materials do not work as dressing for foundation gardens. They will simply wash away. Similarly, very small aggregate and gravel have a way of disappearing. Crushed aggregate, river rock, or field stone in the two-inch average diameter range is an excellent choice.

Tools & Materials

• Excavating tools
• Folding rule
• Garden rake
• Grease pencil
• Hand maul
• Hand tamper
• Lawn roller
• Level
• Masons string
• Rototiller
• Spade
• Utility Knife
• 6-mil black plastic
• Chalk line
• Edging spikes
• Gravel
• Hose
• Landscape edging
• Landscape marking paint
• Perennials
• Spun bonded landscape fabric
• Stakes
• Straight 2 x 4

A pathway that steers water runoff away from the house, keeping it out of the basement, is created by crushed rock groundcover laid over a plastic water barrier.

Using an 8-ft-long 2 x 4 with a level on top, mark where the grade needs to fall at the house in order to produce a minimum 4 drop from the house to a point 8 ft. away Repeat the procedure every loft, along the foundation wall. Connect the grade points with snapped chalk lines, Clear all plantings, landscape rock, landscape fabric, and other debris from the construction site.

Dig out a trench along the lower edge of the garden area, tossing the soil back toward the high end of the garden to begin the regrading work. Relocate and add soil as necessary until the minimum slope is achieved.
Tamp the soil with a hand tamper or roll with a lawn roller.

Install landscape edging (inset photo), and then lay two layers of 6-mu black plastic over the excavated area, running the plastic up the wall slightly. Sheet plastic comes in wide enough rolls that you should be able to install seamless layers.

Plant hardy perennials or evergreens and then pour a 2 to 4” layer of crushed rock or gravel in the foundation garden. When planting, cut an X into the sheeting layers and build up the soil in front of the hole (underneath the plastic) to create a small dam that will help retain water for the plant. Smooth out the rock with a garden rake oriented upside down so the tines don’t puncture the plastic sheeting.