Lime mortar is enjoying a revival and is being promoted by conservation organisations for restoration work and by environmentalists as an environmentally friendly material. It can be used for new build as well as for restoration and conservation work. Some of the benefits of lime mortars are that they allow walls to breathe, are relatively flexible (accommodating some movement), give some protection to surrounding brick and stone against salt and frost damage, 'self-heal' when exposed to air, and allow brick and stone to be reclaimed after demolition. This Good Building Guide gives guidance on the properties of lime mortars, mortar mix design and working with lime mortars. However, customary practice varies within the British Isles and the reader is advised to make sure that proposed works comply with local specifications, especially for heritage buildings. Some helpful further reading is listed. 8 pages.