I'm having a debate with my contractor about sloping our outdoor stairs. I hope to have 1% slope because we get a lot of rain. But because the steps are rounded, my contractor says the difficulties may result in rather dangerous rise discrepancies. Any advice how we can solve the sloping or should I just make them flat?

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  • Just to clarify: +80, +60, etc. - are those # of cm above some base level? Dec 25 '19 at 18:30
  • 1
    Yes. Street level is 0.
    – stelle
    Dec 25 '19 at 18:34
  • Are these to be wood or concrete steps?
    – Jack
    Dec 25 '19 at 19:04
  • 1
    the main problem I see is the discrepency between the front and the side treads, at 5% slope and assuming the deck to be 3m wide the steps at the front (next to the green bit) are in total 60cm high, while at the side (next to the wall) after 300cm of 5% rise less 300cm of 1% rise they are only 48cm high.
    – Jasen
    Dec 25 '19 at 20:54
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    @Jasen Yes there will be that going on. The difference could be split from the center of the arc so that one side is a little taller and the other side a little shorter. Or the difference could be calculated overall and slightly taper the bending forms that will make the risers so that at any given path a person may take up the stairs, the rise will be uniform. With concrete form work, this will be pretty easy but it would be trouble for the tile setter, to a degree....Only on the risers. Tiling the risers first would make it a bit easier...
    – Jack
    Dec 25 '19 at 22:17

Since they are concrete steps, slope them from the radius point. All the risers will be the same and the only difference will be at grade, which would be the same problem without sloping the treads. For that matter, the whole assembly can or could be pitched a little or all of the 5% slope to minimize the difference at the first riser.


I have not checked to confirm if it still holds true, but in the U.S., outside steps are required to have slope, but not to exceed 1/4" over 12".

To help picture this in words, if to make every tread level, the riser needs to be 20 cm tall. To make each one slope, reduce the height of the bending form to make the riser 5-8 mm shorter and raising the concrete form so the top of the forms are at finished height. This will automatically pitch the treads.

  • Thank you so much, Jack. This is really helpful.
    – stelle
    Dec 26 '19 at 11:09

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