DIYbanter - View Single Post

In article .com,
writes:

Had exactly the same problem about 2 years ago. Bricked up a window and
had to rended the surface to match the house. Problem was the render
had to be about 1 inch thick ( given my inset bricks) so I put it on in
two layers..First layer went on fine...Left it for about 4 weeks during
which time it also got a bit dusty, then got around to doing the second
before chucking lots of wee pebbles at it to match the house. 2 weeks
later I thought it looked blown and tapped it..HOLLOW sound. prodded
away and the whole 2 feet by 4 feet lump slid off! Kind of realised
what I had done wrong..Got out watered down PVA solution and soaked the
wall in it..Really soaked the wall until it stopped drying out quickly
then re-did the render.. Suffice to say its still up there!

Sand and cement should really be recoated in 24-48 hours (might
stretch a bit longer if it's cold). Any longer, and it needs to
be handled not as a recoating, but as a scratch (base) coat
application, as you did.

--
Andrew Gabriel