On 09/08/2020 21:38, John Rumm wrote:

There are ways of cheating with that - like screwing up vertical battens
to the wall about 4' apart and getting them plumb and co-planer. Then
slap the render on, and rule it off using the battens. Let it go off a
bit and remove the battens, then fill in the gaps.

Same idea as when you're concreting and there's nowhere to have shutters
round the edge, so you put the shutters somewhere in the area then pull
them out and shove more concrete in the holes.

Bill