Drainage - Gully height

[bill]

I am setting my gullies into position ready to drain a stone patio.I have established the fall to them and at what height they should be if set to the surfice of the flags.Should they be set dead level and notched tight to flag or should they be lowered slightly down with a wider notch(say 10-12mm leaving a similar width to the flag gaps) and haunch the pointing down to the gully thus helping to speed up water despersal and if so by how much should they be lowered.
Many thanks.

[GB_Groundworks]

http://www.pavingexpert.com/drain06.htm have a read of this first

[bill]

Had a look and it refers to linniar drain being set 3-5mm down,I wounder if it should be different for a gullydrain only 6" square.

[GB_Groundworks]

i'd still set it down in the region of 5-10mm and angle the pointing down into it

[lutonlagerlout]

I always have the lip of the flags 10 mm higher than the gully and 10mm back as well to get a full joint between flag and gully
LLL