Wet Dash will not stay on

[tomfromfife]

Hi,
I am not a plasterer but have carried out some property renovations and conversions.

I own a house in Fife which was built around 2007. It is wet dashed externally.
A section of the wet dash became hollow and cracked around 2009 and the builders stripped it off and re applied the wet dash. The wall in question is the rear wall of the integral garage and is single concrete block. On the blocks is a a cement render then, originally, the wet dash. When the wet dash was stripped the cement render was not removed, an additional cement render was applied and then the wet dash.
In 2013 the same happens. The wet dash became hollow and it cracked. NHBC agreed it was a claim and the builders (Stephen Homes) agreed to have the work done. The builders replaced the wet dash and the same happened. I tried to say to them that maybe they should look at the original render but they didn't and replaced it yet again and now it is hollow in places again.

What should the builders be doing to fix this? Should they remove the original render from the concrete block wall as that appears to me to be the common denominator?

Any advice will be welcome....thanks
Tom

 

[malc]

i would strip the wet dash off. if the first coat, scratch coat is hollow then take that off , if not apply a coat of sbr to the scratch coat, and apply another scratch coat with a good scratch. whilst the sbr coat is still wet, do not let it dry out. as the first scratch coat has lost its key for the wet dash. leave to cure for a week then wet dash.

 

[johniosaif]

I would ask them to take it all off now, you can't tell what's good or bad or how long it will last, start again from scratch so to speak

 

[stuart23]

I think it's the new render going onto old render that's not been prep'd right. As above strip back and redo.

 

[church]

its not being done right , wetdash is the most hard wearing render finishes you can get , they have tried to cut corners imo cause its a job for nothing .