I'm planning to build a fairly small patio at the back (2.5m x 2.5m), and instead of pavers I will place concrete slabs (60cm x 60cm x 4cm). Would it be fine to use construction waste, such as concrete lumps, bricks pieces, fist-sizes rocks for the first layer base, and stone dust as the second layer? If so, how thick I should have the first layer?

If it matters, I'm in Canada, Ottawa, and in this area we normally don't expect lots of water to drain, so I think this fact will affect the base structure.


1 Answer 1


Surely you can but there a couple of things to consider. Concrete should not be less than 2 inches, so based on a 2x4 as your footing/frame I would not add more than 1.5inches of base loose pieces. The other thing is expansion as it cures. So you may want to add chicken wire overlay and use large enough pieces of concrete where you can tie the concrete pieces with wiring to the chicken wire. This will allow for the concrete to stick and stay regardless of expansion during the first 3 days of curing which is the most important.

If you are using crushed pieces then I would just make sure to tamper the rocks very well so the no sinkage occurs over time.

  • Thank you. Could you give some idea on how to estimate the amount of gravel required for the base?
    – Mark
    Sep 2, 2016 at 12:11
  • Hello you are welcome. What we use for a rule of thumb is 1 yard = 80 sq ft @ 4inches thick. Mind you that formula based for materials such as crushed gravel, sand, topsoil and concrete Sep 3, 2016 at 6:28

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