When paving an area, at what point is drainage required?

We have a courtyard that is pretty much enclosed on 4 sides (with an opening for a path beside the fence).

The space is 2.5m x 3.3m. The courtyard is surrounded by:

• back wall of garage.
• two walls of house
• fence (neighbours house is 1 foot behind fence)

We are looking to pave this space. At the moment there is no paving and no flooding. There is no drainage but rain water soaks into the ground. If we were to theoretically add a single paving stone, then drainage would not be necessary. And probably the same if we added two paving stones.

But if we were to keep adding paving stones, there will come a point where simply letting the water run off to the sides is not sufficient. And at this point drainage becomes necessary.

Is there an industry standard set of rules (or best practises?) used to determine if and when drainage is necessary? Or is it a 'that looks about right' assessment?

You don't want to create a wet area.
You can't drain your water to neighbors land or council land ect.

You could dig out the area and use type one stone and drain water to base..
Also it depends on what your paving with, block or slab ect

You could leave say a 100mm wide gravel strip around all perimeters.

freddiemercurystwin said:

You could leave say a 100mm wide gravel strip around all perimeters.

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Thanks @freddiemercurystwin I guess you are referring to something like this? https://www.pavingexpert.com/drain14
But what makes you say 100mm is wide enough? e.g You've had X years of experience and 100mm just feels right, or is it a rule of thumb, or some industry standard?

At some point 100mm would be insufficient. (e.g. 100mm would obviously be insufficient for a football field sized 'courtyard'.) I'm just wondering if there is a calculation that can be done for this that says something like "An area of X.Ym² requires an infiltration drain of size Z."

lonner said:

Also it depends on what your paving with, block or slab ect

Click to expand...

Thank you @lonner We are looking at using a circle kit of Marshalls Drivesett Tegula and then expand the circle as far as possible.

I am hoping it's okay to use driveway paving blocks for a courtyard that will only ever be walked on?

100mm around the outside would give you a clear drained area of 1.16m2, ample for a paved area of 7.1m2.