An introduction to lime - The Hempcrete Topic: Designing and Building with Hemp-lime - page 66

Traditional buildings were kept healthy by the breathability of building lime. The walls of this cottage
are built from a combination of natural materials: stone, brick and a timber frame. Lime was used in
bedding mortars for the masonry, and probably in the wattle-and-daub panels in the timber frame,
as well as in the plaster and render.
An important rule of thumb when considering the construction of a wall is to have harder,
less permeable substances towards the centre of the wall, and softer materials, with greater
permeability, towards the outside. This favours the transportation of moisture out of the
fabric of the wall. It would therefore be advisable, taking a stone wall as an example, to use
a moderately hydraulic lime for the bedding mortar, and to point and render with feebly
hydraulic lime or air limes, rather than the other way around (see photo on page 48 ) .
An overview of the types of naturally occurring lime, with their main characteristics and
examples of each type, is given in the table below.