Lime Render/Harls

Lime mortared and rendered stone buildings in Edinburgh have a natural ability to both hold and evaporate moisture from the walls, thus maintaining a state of balance with the surrounding atmosphere.Lime mortars and harled or rendered surfaces can therefore absorb and evaporate moisture freely.

Lime coatings were widely used as external protective and decorative coatings. External coatings of lime mortar are still the most effective method of weather proofing solid masonry walls.
Lime renders were traditionally applied to give protection to walls built of poor quality rubble stone, porous brick or to walls in exposed locations facing driving winds.

They help by acting like a sponge, absorbing rainfall then allowing it to evaporate rather than soak into the wall. Most cottages and houses built of rubble stone would have been rendered originally and they tend to suffer from penetrating damp if the lime is removed or replaced with cement rich render.