Discoloured Render - splashback?

[sh4d0w]

Hello all,

I am looking for some advice on this issue at home, We had an extension completed just before last Christmas (so 14 months ago) and the "patio" has been like this ever since; I am just getting round to sorting it (another post on this). I have noticed some stains on the bottom of the render and in places some green mould or algea.

Currently, the patio area sits 2 bricks down from DPC (150MM) as per regs but there is no drainage etc could the stains be caused by driving rain or splashback from the ground?

How best to sort it and clean or treat it as obviously i cant set to it with the pressure washer or scrubber.

What can i do to prevent this once Indian Sandstone is laid? (i am going to look to drop this in at about 100MM clear of DPC, the patio will fall AWAY from the house and an Ako or equivalent drain at the end. Would it be worth installing one against the house too?

PS, please ignore the mess, Skip pending and A 4 month old with more stuff than our 11 and 13 year old ever had combined.

 

[sh4d0w]

Anyone??

 

[^woody^]

This is common with lots of modern render where the drip is not properly formed and the bottom of the render holds moisture. Algae stainging is not far behind.

Another possible cause is pattern staining from a blocked cavity and thermal bridge. But I suspect the drip looking at the pattern.