Currently preparing an area in our garden to lay a paved patio area and pergola (the latter being provided by a professional).

My wife and I need to build a supporting wall around the sides and at the top side (see the photo below).

patio area

We have been advised to create a 1% incline on the slabs, so that water can run off when it rains etc.

My question(s) is, how do you measure out/figure out how to do this? Is this a requirement when building a patio area? Is 1% the ideal incline?

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    The good news is if you haven't done this before you have about a 99% chance of having at least a 1% gradient! – DMoore Mar 14 '19 at 20:36
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    Math: For every 100" run, you would have a 1" drop. So, for about every 8' of length, the patio should fall 1". Inches of run * 0.01 = inches of drop. That said, I'm not sure what gradient is appropriate. – JPhi1618 Mar 14 '19 at 20:39
  • What “slabs” are you referring to ? – Alaska Man Mar 14 '19 at 20:48
  • @Alaskaman I am referring to the paving slabs (not pictured) – Shaun Mar 15 '19 at 17:36

You want the grade to be in the width, not the overall length of the patio. The fall should point in the direction away from the home. .01 × (width of the patio in inches) = the height difference. I/E: If the patio is 8' wide, 96 inches x .01 = .96 inches. So the height of one side needs to be one inch higher than the other.

To my knowledge there is no building code for fall requirements on a patio. 1% is a very shallow fall. I would grade it at 2% (1/4" per foot) for a better fall without it looking weird to the eye. 2" over an 8' span isn't going to be very noticeable.

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For all intents and purposes a 1% grade is 1/8" per ft and 2% is 1/4" per ft. 1% percent is the absolute minimum grade allowed for drainage but your concrete is susceptible to having bird baths in the center if you are not extremely careful when you pour you slab.

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