Author: Woodsworth Housing Co-op

Commentary:
Without proper drainage, that is, surface drainage and subsurface drainage, the following may occur:
–  water may soak into the building foundations;
–  the patio itself may settle/subside, throwing it off-level;
–  general flooding may occur;
–  landscaping may be ruined;
–  and insects and bacteria may breed in standing water causing health issues, etc.

Descriptor and remedies –
Our midrise patios use 2’×2′ cement tiles, with gravel underneath.

Between these tiles there are gaps which are needed for drainage. They should be filled only with sand and kept free of soil, clay, and weeds ;

To avoid /prevent clogging with in the gaps and into the gravel, a geotextile layer (landscape fabric) can be useful. This would also prevent the drain pipe from becoming clogged with weeds, soil, dirt, debris, and gravel ;

There should be a gradient (pitch, slope, fall) towards the drain, of at least one percent ( 1 %) — or better still — two percent ( 2% ) . This would represent the equivalent of a quarter inch (¼ ” ) for every foot (1.0’) or three and a  quarter inches (3 ¼”) for thirteen feet (13 .0 ‘) .

** For future reference only : — the so-called “French drain” might also be used for patio drainage. This drain is a lined ditch, filled with gravel, sloping towards the drain.

Addendum to the Maintenance Committee minutes of September 13, 2017.