I have had my house re rendered and it went cracked and hollow sounding in patches in a very short time - less than a week. The plasterer came back removed the render and re did it, I have left it for 2 weeks and have come to paint it and again it is hollow sounding with hair line cracks around these areas - Is it OK to paint or do I get him back again to re do it - If he will !!

Gareth, October 2009

Sand & cement will display those symptoms if the wall has not been scudded properly before the sand & cement coats were applied. A very sloppy but strong (plenty of cement) mix of sand & cement is thrown against the wall using a dasher to give the next coat a grip. The first coat should be a scratch coat - i.e. keyed to give the final/float coat a grip.

JD, October 2009