Building lime knowledge

Lime, in the form of mortars, renders, plasters and paints, is a key component of old buildings and essential to their repair – or at least it should be. Today lime-based materials are also emerging into the mainstream and being used within low carbon construction systems, employed in everything from homes to superstores. All this becomes clear in the new Lime Briefing from the Society for the Protection of Ancient Buildings (SPAB), published in association with the Building Limes Forum, that I’ve been lucky enough to have had the job of editing.

Anyone who has used lime will know that it’s a versatile natural material and, through the words of some of the leading practitioners in the field, the Briefing explains the exciting role lime has to play not just in conserving our heritage but in the future of our built environment.

The key attribute of lime based materials is their breathability. Indeed, one contributor explains that they are ‘the Gore-Tex of the building word’, allowing water vapour out of a structure rather than trapping it. Lime also has many other properties, not least its ability to accommodate movement due to its flexibility and self-healing nature and the fact it’s pleasant on the eye.

We know the ancient Egyptians were using lime in the construction of pyramids by 4000 BC so the material has a proven track record of over 6,000 years. Yet, in the early 1900s, cement based products started to replace lime, often with disastrous consequences for old buildings. Indeed, many of the problems relating to damp and decay that I’m asked about today relate directly to the use of inappropriate modern materials instead of lime.

As Douglas Kent, the SPAB’s technical and research director, makes clear in his introduction to the Briefing: “Lime is not a relic technology as some would claim. Far from it, lime has real, practical benefits and is at the forefront of a number of exciting developments in both conservation and sustainable construction”.

Download the SPAB Lime Briefing free here.