cracks in render

[fisons]

hello to the forum. I'm an occasional renderer, visit the forum regular and this is my first post looking for advice.Customer asked me hack off the blown areas of render off concrete block garden wall. Its been redone in past in s&c and cracked along the lines of the blockwork courses then leaked and blown in winter.
I like 4:1:1 and 6:1:1 and always thought the lime accommodated any slight expansion, but on recent visit saw cracks on a half brick thick garden stairwell I rendered about eight years ago. I'm no good with putty paddles but did use a lime and sand ready mix about a year ago to repoint, has anyone used this to patch walls. Thanks.

 

[SPREADS]

Could be a few things ,was it scudded,brick needs to be scudded well and even sealed with Sbr,the block walls leaked?must be a high bank behind it ,this could be why it's cracking and blowing in places,could be movement from the bank if its only a four inch solid in edge

 

[DannyMac]

Is it a retaining wall, does it have copings on top, is there an adequate footing?

Meshing the scratch or putting fibres in the mix can stop a certain amount of cracking.

 

[fisons]

thanks for reply.Brick stairwell I scudded and Feb slurried. The blockwork wall I'm to render is the side of next door's slightly higher concrete driveway.It does take deflected water from driveway surface.I guess I'm expecting lime & sand like an elastic band.

 

[fisons]

No copings stones. Customer's garden is slope. Next door's drive way is flat concrete raft about 18" thick . Wall is low, long triangle. Hacked off blown render at ground level at big end to see base of the raft and about 5"of earth below that.