How to achieve a 1% gradient

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).

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?

• 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 at 20:36
• 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 at 20:39
• What “slabs” are you referring to ? – Alaska Man Mar 14 at 20:48
• @Alaskaman I am referring to the paving slabs (not pictured) – Shaun Mar 15 at 17:36