The Historic and Sustainable Mortar and Plaster Binder
Lime, which is composed primarily of calcium carbonate (limestone), has been used for vast millennea as the binder which holds aggregates (sands, hemp hurd and other organic in-fill) together for historic mortars and plasters. It has many admirable properties that make it the material of choice once again when repairing traditional vintage structures and building new sustainable buildings. With a high vapor permeability lime allows masonry systems to breathe by processing moisture back to the atmosphere and keeping moisture from becoming trapped within the the core of walling. Trapped moisture leads to mold and rot and poor indoor air quality. Lime has a high modulus of elasticity which helps a structure to accommodate slight movement without putting stress and cracking a whole wall system or individual masonry units which make up a structure. Lime is immune to sulfate attack. With these few properties, along with many others, the pairing of the right lime with the corresponding application where it is best suited makes lime “Fit for Purpose” as a superior building material. Overall, the cost impact when incorporating the right lime into a building campaign is very low because if offers a long service life while it has a positive environmental impact. Lime is considered to be close to carbon neutral. The embodied energy needed to produce lime is low. As lime cures cures it then absorbs CO2 from the air. For the perfect material in creating an external shelter to a sustainable building or for being integral to the heart of what a building is made of, internally plastered in and painted with, consider lime.