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.

Drainage Solution: How to Build a Dry Streambed

A dry streambed or watercourse (also known as an arroyo can be built to direct water runoff away from your house foundation and toward areas where the water can percolate into the ground and irrigate plants. When designing your dry streambed, keep it natural and practical. Use local stone that’s arranged as it would be found in a natural stream. Take a field trip to an area containing natural streams and make some observations. Note how quickly the water depth drops at the outside of bends, where only larger stones can withstand the current. By the same token, note how gradually the water level drops at the inside of broad bends, where water movement is slow. Place smaller river-rock gravel here as though it had accumulated in a natural stream.

Large heavy stones with flat tops may serve as steppingstones, creating paths to cross or even follow dry stream beds.

The most important design principle for dry stream-beds is to avoid regularity. Stones are never spaced evenly in nature nor should they be in your streambed. Also, if you dig a bed with consistent width it will look like a canal or a drainage ditch, not a stream, so vary the width and the depth. Consider other yard elements and furnishings. For example, a dry streambed is essentially a river of rock. so it presents a nice opportunity to add a landscape bridge or two to your yard.

Contact your local building department before deliberately routing water toward a storm sewer; this maybe illegal. Before digging, call your local utilities hotline to have buried pipes and wires in or near the construction area flagged.

Tools & Materials:

Garden rake
Landscape fabric 6-mil black plastic ¾ to 2” river rock 6 to 18”- dia.
river-rock boulders
8-thick stepping stones Native grasses or other
perennials for banks

A dry streambed can be constructed to direct water runoff away from your basement walls and to add an attractive landscape feature to your yard.

Excavate the streambed to about 12’ deep, working within a no regular outline. The streambed should originate at a downspout from your gutter system. Follow the natural course of rainwater runoff where possible. End at a natural sink, such as a rain garden. Bends are often wider in natural streams, so make your stream wider at bends. Rake, smooth, and compact the soil within the project area.

Lay strips of landscape fabric over the excavation area, overlapping fabric by at least 12° at seams. Lay the fabric to within 2 to 3 ft. of the house, and then lay a strip of 6-m black plastic next to the house to direct water away and into the streambed. Weigh down the edges of the fabric with some of your larger rocks.

Place rocks in the streambed, beginning with larger boulders along the streambed banks. Extra excavation maybe needed to properly set extra large boulders. Fill around large boulders and line “rapids” with smaller boulders. You may also place stepping stones to make a pathway or bridge in an area where you’re likely to be walking. In most cases this feature is mostly ornamental.

Fill in spaces and create gravel bottoms with river rock in the ¾ to 2’ size range. Make sure the river rock you’re using is native to your area, and avoid dumping it all into a flat field. Retain some nice shapes and contours Trim off any exposed landscape fabric and plant native grasses and other perennials along the banks.