I have a fairly small balcony that I don't use, but my apartment has no garden. Would it be possible to cover the balcony in a tarp and then add some soil, moss, plants, etc?

It's a solid construction, made of concrete and treated wood. I was thinking of starting a little biology project there, nothing heavy. Is this feasible?

  • Might want to check building codes in your area. You'll be adding a lot of mass to a balcony that may not be designed to take the stress. Commented Nov 27, 2016 at 16:15
  • Check that at Home Improvement stack. Commented Nov 27, 2016 at 17:22

3 Answers 3


It's certainly possible to create a 'roof' or balcony garden, but not easily. The depth of soil to aim for is preferably not less than 18 inches, and usually, drainage pipes are laid into the roof/balcony prior to installation, to deal with excess water for drainage purposes. What you're proposing won't really work, drainage will be very poor, and if the door to your balcony opens outwards, the depth of soil required will mean you can't open the door, and the soil would also be sitting against the building's walls, which really isn't a good idea. But that doesn't mean you can't grow plants, just use containers instead - the bigger the container, the larger the plants you can grow in it. I have a balcony, its not large, but its got plenty of plants, including climbers. You should consider the question of light though - if the balcony is south facing and gets plenty of sun year round, that's a completely different growing situation from one that's in permanent shade. Winter temperatures might also be a factor - if your winters are always very cold and below freezing, smaller containers are at high risk of freezing solid, which will kill any plants growing in them.

UPDATE: You've said you were thinking of using planks to hold the soil in place - just use more planks to make a bottom, raise it up off the balcony a little and it'll have drainage through the gaps in the bottom, between the planks.

  • I was thinking of using planks along the edges, sort of like a giant flower box, with space so that the door can open. Just seemed like a pretty fun project
    – user386094
    Commented Nov 26, 2016 at 16:35
  • I wouldn't recommend it - high risk of drying out, onerous to water, water flooding everywhere when you do water, restricted root depth - use trough like containers instead.
    – Bamboo
    Commented Nov 26, 2016 at 16:37
  • @user386094 If you're going to construct something with planks, just use planks as the bottom as well - raise it up off the balcony surface and then it'll drain between the gaps in the planks.
    – Bamboo
    Commented Nov 26, 2016 at 16:58

Yup, I see lots of problems with this idea, sweetie. Is there a reason you don't want to use pots? I wouldn't bother trying to make a 'roof top garden' on a small balcony. Just get a collection of great pots (all tied together by material, color, shape to not distract from your plants) with drainage holes, get wider than tall. You can use tall, narrow pots turned upside down to support and raise some pots to make more use of the vertical dimension. So much can be grown in pots successfully. Don't forget hanging baskets making even more use of your area in 3D. You HAVE to use bagged sterilized potting soil!! You need drainage holes. A way to lift the bottom of the pots off of the surface they sit upon. I'd even purchase bottled water if I had treated city water out of the tap. No rocks no gravel beneath the soil and above the drainage hole. What is your zone? What is your orientation to the sun? Are you on the north side of the building or south for instance. What is the usual direction for wind? If you've got a winter, you will have to drag all of those pots inside, or you'll not get the perennials back in the spring. If you asked your management for the building, your association you'd probably get a big NO WAY. But pots are different, they are movable. There are ways to protect plants in pots for the winter. And when moving all plants indoors for the winter, you have to do it slowly, not all at once. To get the plant used to the environment indoors, they have to be taken inside for a couple of hours and then back outside. This continues increasing the time spent inside for a few weeks before your plants are ready to live through the winter indoors. Same thing in the spring to harden them back to living outdoors. How big is this balcony? I've done Landscape designs for decks, balconies with pots big enough for trees, water walls, lots of other smaller pots to tie all together. People were part of the design, to be able to sit among the plants, water sounds and grasses, trees that sway in the wind. Never was there any idea to making the surface of the balcony mimic the normal garden surface. Not a good idea. All that work and expense could be focused on pots, soil, automatic watering systems, an indoor winter area, wheels on the bigger heavier plants and christmas lights and burlap to wrap the trees and their pots to survive the winter. Oh, you could also get water filters for your tap water to get rid of the crap they put in your water and that would also be very good for you as well. There are those skinny coiled hoses to screw onto your faucet (make sure you can do this or you'll be purchasing a new faucet)...they are easy to use and pop back into a coil. Beneath the pots should be air space (lift with pot feet or tiles) then some sort of a tray to collect excess water and then use a tiny hose to siphon it away from the balcony beneath and the architecture. You don't want to piss off your neighbors beneath or cause water streaks on your building.


As promised here's how it looks like after ~20 months of operation.

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Surprisingly for a non-drained container, water hasn't been a problem. My rationalization is that the larger plants have developed far-reaching roots which can supply the plant even if water is pooled in a specific corner or bottom. And the tiny plants I water regularly because I fear they lack such roots yet.

Composting and Pests

The garden being 1. indoors(virtually a heated greenhouse) and 2. tiny (compared to a vegetable field) pests shouldn't be a problem.

Yeah, right. Anaerobic compost takes 2 years minimum. I applied it after 1 year. To this day I am spraying poison in hopes of getting rid of all the types of flies and ... things.

Another point is that this is how it looks after 20 months of no nutrients added to the soil. When the soil was strong it was a jungle!


The vital part. Based on my experience constructing this thing I would recommend:

  1. Apply plastic liner tape to all corners.
  2. If any of the surfaces have irregularities larger than ⌀1mm (as in: if this was your new living room you wouldn't directly paint over it but you would plaster it first) purchase "water resistant cement mixture" and make it as even as possible.
  3. Purchase "water insulation in a bucket" or "or water insulation for application with a brush". It's a gray goo. You need LOTS of it, I used about 100 liters. Apply 3-4 tick layers to all surfaces in future contact with the soil.
  4. Now the layer between the water insulation and the soil. I have used a plastic sheet which is the worst idea I can think of. An improvement would be "swimming pool liner" - a tick plastic sheet. And - obviously - the best would be floor tiles. Do keep in mind those do not void the requirement for solid water insulation layer beneath.




If you are extremely lazy and incompetent: whole summer. Else: no idea.


Are absolutely zero problem on this scale. I even grow them on purpose to increase biological diversity. Also the cat likes eating them.

Structural Integrity

The dashed walls on the drawing are load-bearing(despite the internal window to the right; however the to-the-outside window on the left is not load-bearing thus the garden doesn't reach it).


Current soil depth(it was much more shallow when the jungle of tomatoes took over): 17cm.

Maximum soil depth(limited by the cutaway; I am scared to add more weight than that): 30cm.

Bill of Materials

  • Ytong aerated cement blocks, 300x600mm.
  • A bag of cement and two of sand.
  • Water resistant paint (the brown thing). This thing is everything-resistant so be very careful not to make the house or Your skin dirty. Also it was 15 years past expiration date - but worked like a charm!
  • A leftover wooden tile(the blue thing) from the floor in another room.
  • All the water insulation mentioned above.

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