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DIY Rain Garden

DIY Rain Garden

Imagine a garden that is not only a beautiful haven for you and the birds, bees and butterflies, but also reduces erosion and helps keep groundwater cleaner. Knowles Building Centre has some ideas to make your rain garden dreams come true.

Rainwater gushes from downspouts into the streets and storm drains, carrying with it an unhealthy mix of fertilizers, pesticides, motor oil and other contaminants. A great solution is the rain garden, which reroutes precious rainwater and melted snow directly from your home’s downspouts, letting it seep into the deep porous soil, and reducing runoff. This results in less water ending up in the storm drains, ultimately protecting our natural waterways from runoff pollution.

If you have the space in your garden and are interested in helping our environment, the rain garden is the perfect DIY project for this spring. 

Planning Your Rain Garden

First, assess your property and house with this handy checklist:

  • Check how rainwater flows off your roof, driveway and pathways
  • Make a note of downspout locations, blockages in eavestroughs, and where the water flows on the ground, hopefully away from your foundation
  • Observe the slope of your yard
  • Have you noticed any pooling or streaming in your yard after a rainfall?
  • Where are trees and tree roots?
  • Where are utility lines?

Where to Install Your Rain Garden

Start planning by determining the best place in your yard for your rain garden. You’ll need a fairly flat area that slopes only slightly, from one to five percent. Keep it at least ten feet from your home’s foundation as well as your neighbour’s foundation. Ideally, build your rain garden at the bottom of a slope where water from a downspout will find a direct route.

Where Not to Install a Rain Garden

Installing a rain garden on a slope steeper than 15% can lead to flooding. Make sure your rain garden is at least 50 feet away from steep slopes.

Keep it far from tree roots and utility lines hidden beneath the surface. Check with your local utility company to locate underground wires before digging.

Steer clear of septic beds, with a distance of at least 13 feet from your rain garden.

Calculate the Size of Your Rain Garden

Your rain garden can be as large or as small as you like, depending on the size of your property and the area of your roof. It will need to be big enough to handle the anticipated runoff from your roof, lawn, and any hard surfaces such as a driveway or path.

If you have the space, why not build more than one rain garden on your property?

A good rule of thumb to follow is the one-tenth rule – the rain garden surface should be approximately one tenth the size of the area draining to it. To calculate this, measure the area of your roof and divide by ten.

Design the Style for Your Rain Garden

Use a hose or rope to mark the shape of the garden you want. Create a rain garden to complement the style of your home or garden.

Do you like the natural free-flowing look of a wildflower garden? Maybe you prefer a more ornate, formal or traditional garden style?
It’s all up to you, so have fun designing your unique rain garden.

Sources of Rainwater for Your Rain Garden

Simply add an extension on the end of your downspouts directly to your rain garden. Build more than one rain garden to take advantage of captured rain in the front, back or sides of your home. Rain barrels are a wonderful way to make the most of rainwater, and keep your water bill down. A readily available source of water for your plants and trees in the hot dry summer months, your rain barrel may make you eligible for a credit from your municipality. Extra rainwater in your barrel can go directly to your rain garden.

What Type of Soil is Best?

What kind of soil will you need? Rain gardens need sandy, well-draining soil, about two feet deep. If your garden has mainly clay soil, you will need to amend it. Dig out about two and a half feet of your soil and replace it with a mix of sand and compost.


  • Garden rake
  • Shovel
  • Edger
  • Wheelbarrow
  • Bucket
  • Hose
  • Hacksaw
  • Sod cutter
  • Pointed trowel


  • Soil – amount and type of soil depends on the type of soil currently in your garden
  • Mulch – Natural, shredded mulch rather than wood chips
  • Plants – native, drought resistant, a mix of larger and smaller shrubs, trees, and plants
  • Rocks – to be placed in the inlet and outlet
  • Landscape fabric
  • Downspout extensions

Create the Rain Garden’s Shape

Using a hose or string, mark the border of your rain garden area and basin. Cut the edge of your garden bed with a shovel or edger. Lift up the sod around your rain garden basin.

Dig the Basin

Now for some deeper digging! Dig 20 to 30 inches deep to make the basin. If your soil is sandy, 20 inches will be deep enough. Use the soil you are digging out to create a berm around the edge of the basin.

Dig the Inlet and Outlet

Dig a shallow channel or inlet to encourage the water from your downspout to flow into your rain garden. To reduce the risk of your rain garden overflowing from heavy rain, dig an outlet to transport water out of the rain garden, away from your house. Use landscaping fabric to line your inlet and outlet. Place some decorative rocks in the inlet and outlet to help filter the water and reduce the speed of the rainwater.


Plant shrubs and small trees around the perimeter of your rain garden. Depending on the type of soil in your garden, you may need to mix some sand and compost into your basin soil to ensure proper drainage. A good ratio is 60% sand to 40% compost. Plant the smaller plants you have chosen to complete your rain garden.

Mulch and Water

Spread shredded mulch thickly over your garden. Replenish as needed over time.

Water your plants regularly, especially in the first two years, even if they are drought resistant.

Monitor the inlet and outlet for obstructions to help your rain garden do its job properly.

Now it’s time to sit back and enjoy your beautiful rain garden.

If you have any questions or need more information, visit Knowles Building Centre. Our team is always available to help in any way we can.

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