Andy Fleming writing on urban homesteading

As a successful homesteader, you’ll need the ability to make full use of their surroundings. Being able to adapt every square inch of space into something useful will dramatically increase your self-sufficiency.

Windowsill gardens and hanging planters are a great way to turn unused space into a source of food and air purification. However, most people never consider the fact that a flat roof can also make an excellent full-sized garden. These are often referred to as “living roofs” or “green roofs”, and they make a great spot to grow smaller vegetables, herbs, or flowers. If you’ve got a vegetable garden, consider adding a flower garden to a nearby porch roof to attract bees and increase your overall yield.

First, you’ll want to locate a flat section of roof, and make sure it’s strong. If you’re putting in a new porch or deck anytime soon consider planning for a living roof with plenty of joists for reinforcement. A living roof can weigh as much as 150kg per square meter. You can always consult a local builder or engineer to see if your roof is adequate.

For the actual build, you’ll need:

  • Two layers of pond liner
  • One layer of “weed barrier” or “root membrane”. This can be found at any garden center, usually used to keep weeds from growing under decking. Here’s an example.
  • Two layers of gravel.
  • One layer of moisture blanket. This helps trap moisture in the soil, and will aid in keeping your garden maintenance free. You can save money by using regular blankets or cardboard, although these should be checked during the winter and replaced if rot occurs.
  • One layer of woodchips, make sure these are not chemically treated.
  • One layer of compost (optional, but recommended).
  • One layer of topsoil.
  • Self-adhesive flashing tape.
  • Several big stones, small stones, and extra gravel to plug any gaps.

It’s difficult to calculate the heat transfer properties of a living garden. In light of this, you may need to add a layer of traditional insulation underneath the entire garden in order to meet your local building regulations. However, living gardens do seem to insulate just as well as fiberglass or fiber board so it’s probably unnecessary if all you’re worried about is loss of heat.

  1. Start off by making sure your roof is structurally sound. Check for leaks. Then add the optional layer of insulation if you want or need to.
  2. Roll the first layer of pond liner onto your roof. Make sure it’s tucked under any leading you may have at the edges. When it rains, you want water to hit the liner and go into your garden, not under the liner itself.
  3. Cut the liner, leaving a 5-inch lip around the edge of the roof.
  4. Optionally, use the scraps of liner you’ve just cut to go under any drains. You want to trap rain and funnel it into the garden.
  5. Add a layer of gravel, just enough to evenly cover the roof.
  6. Roll out your weed barrier over the gravel.
  7. Add another layer of gravel. This one should be thicker, about 1.5 times as thick as the first layer.
  8. Cover the gravel in a layer of moisture blanket or regular blanket. Anything that will get damp and stay damp should work. Keep a 6-to-8 inch space around the edge.
  9. Add a layer of small stones or gravel on top of the blanket.
  10. Fill the gap around the edge of the blanket with big and small stones. This will allow for drainage and will keep plants from growing into your ceiling.
  11. Use flashing tape to secure the pond liner to the edge of the building. Make sure it is secure, this will keep water from getting under the pond liner.
  12. Time to add the soil. Start with a layer of wood chips/bark to help absorb moisture.
  13. Cover the bark with compost or other nutritious soil. When spreading this layer, take care not to rearrange the wood chips too much.
  14. Add a layer of topsoil, you can gently turn all the layers of soil during this step to mix everything up a bit.
  15. Stomp the layers of soil until firm. You can use a tool, but boots work just as well.

Congratulations! You now have the makings of a perfectly functional living roof. All you need to add are the plants. Hardier plants are recommended, at least until you can see how your garden performs. Starting out with herbs is a good idea, you won’t have to worry about weight or intensive care. You may need to water the garden, depending on rain conditions so make sure to check it periodically.

One more thing to consider, you might want to add paving stones to create a small path across your roof garden. This will allow you to get to the plants more easily. If you have another roof higher up (say, if your garden is on top of a porch) a path will provide a spot to stick a ladder for higher access.

Image: © Benedek

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