The guy building my patio (using 200X100X70 clay pavers) tells me he always lays them on a sheet of plastic DPC which he lays on top the sand bedding layer. Says it prevents rain washing away the underlying sand. I should mention the coarsest sand I could get is building sand - thats what everybody here (Wester Cape of South Africa) seems to use . So far I made sure he followed your construction process - so we have a bedding layer ready for laying. Would appreciate you advice. Great web site - you should put it in for a Phd
Your problem comes when it rains, the water wont be able to escape, dpc isnt the material i would use. I guess if you must use building sand a woven geotextile sheet would be better suited as water can pass but finer sand wont. Is there no other medium available? Maybe a fine chipping?
if that's the proven method in your part of the world then best stick with it. Building sand is a nightmare to screed and if that's all you can get I'd prefer to lay it on grit or dust.
western cape has roughly the same annual rainfall as luton which although fairly dry by uk standards is by no means arid
looks like just a different technique
