I'm utilising a 'drive drain' at the lower (but widest) end of my new patio
(the drain is the long narrow type - bit like guttering with a metal grille
over). Is it necessary to 'slope' the drain (like with guttering)? The patio
is 9 metres in length at its lower end and because of this long run, any
slope would result in the lowest end of the drain being way below the level
of the flags! Because these drains are not particularly attractive I've
thought of setting it below the level of the flags, putting water permeable
membrane over the grille, with decorative aggregate over the top of that.
This would effectively disguise the drain, would compensate for any drop in
level below the flags for a drainage slope, and water should be able to flow
through the aggregate and the membrane into the drain. Anyone see any
problems with this?

Kev