Have you tapped it to see if its blown, ie hollow sounding and hence no
longer attached to the underlying wall.
It might not be what you want to hear, but I had to have several feet of
this removed and re rendered as nothing was holding it on in some places.
One supposes it was water getting behind it and freezing etc.
Brian

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From the Sofa of Brian Gaff Reply address is active
"Davidm" wrote in message
...
Victorian semi, large south facing wall, smooth rendered and painted.
Has some cracks that need repairing before I repaint it. The cracks
aren't huge, 1-2mm wide, probably full depth of render. Just caused by
natural movement from the heat of the sun, most of the neighbours
walls have the same problem, and surveyor says nothing to be concerned
about. No point in filling with mortar, it will just crack again.

Was thinking of doing the following:

Brush out any loose render, dust etc
Apply some stabilising solution/sealant, or maybe diluted pva?
When dry fill with paintable flexible frame sealant?
Use wet sponge to blend in and slightly stipple the surface
Paint with regular Sandtex or similar.

Does this seem reasonable, or any better suggestions?