It allows the building to 'breathe' – as lime is porous, it allows for the collection and evaporation of moisture. Portland cement in contrast, an often applied render for stone or brick buildings, traps moisture behind the stonework, which can result in the erosion of the masonry.
A lime render may be covered by a lime wash.
- Oxford English Dictionary Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009. Render, n2, 5.