There's a lot of disinformation about measuring slope on balconies.
Many people believe you measure it with a 2 m ruler. That's not correct: a 2 m ruler measures flatness (in other words, dips and bumps along the flooring).
Nothing in the standard for testing balcony slope calls for a 2 m ruler.
Israeli Standard (SI) 1555 part 3, 2014 amendment, does mention a 2 m ruler, but for local deviations in flatness.
Flatness has nothing to do with slope. On a balcony, what matters is slope, not flatness.
Section 3.2 of SI 1555 part 3 covers two separate tests: one for balcony slope, and one for flatness, which points to SI 789, where the 2 m ruler test appears again.
Here is section 3.2 of SI 1555 part 3:
And here is SI 789, where the flatness test appears (not the balcony slope test):
Beyond the fact that it isn't required: if a 2 m ruler really were the tool for testing balcony slope, a puddle would technically be allowed, say, if only two tiles along its length had a faulty slope. That doesn't pass any reasonable test.
More proof that a 2 m ruler isn't the right tool: look at slope testing in a shower stall, which requires a minimum 1% slope. A standard shower stall measures 80 cm by 80 cm, so testing it with a 2 m ruler simply isn't possible.
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