In our build (ICF) we're thinking to cover a wall which will form a boundary to a neighbour's garden with cement board and paint that white. It'll be at the back of the neighbour's garden hidden behind bushes and trees so difficult to render. This should match well enough with the existing part of the boundary wall on their side. The wall is on our land. Wall size approx 4.8m wide and 4.8m high (3m being the single floor room and 1.8m being a wall which will form the side of a terrace.