Lime Mortar

Lime mortar is a traditional masonry binder made from calcined limestone, slaked with water and mixed with sand, that hardens gradually through carbonation as it absorbs carbon dioxide from the air rather than through the rapid chemical set of Portland cement. It was the dominant mortar for masonry construction from antiquity until the widespread adoption of Portland cement in the nineteenth and twentieth centuries, and its softer, more flexible and vapor-permeable set makes it the preferred repair and repointing material for historic masonry today, since a harder modern cement mortar can trap moisture and accelerate the decay of soft historic stone or brick.