Lime mortar

Lime mortar was in common use throughout the days of ‘canal mania’ and it can be spotted in numerous examples of canal architecture. It was also used extensively in the construction of the canals themselves - in fact our canal infrastructure is still dependent on lime mortar for its flexibility and permeability.

Pontcysyllte Aqueduct, Llangollen Canal Pontcysyllte Aqueduct, Llangollen Canal

What is lime mortar?

Lime mortar is created by mixing sand, quicklime and water. It has been used for centuries to bond together brick and stone in all types of buildings.

Why is it used?

Roman craftsmen certainly knew their onions. They knew that the foundations of a building will move over the years due to changes in temperature and ground water levels. They also realised that if a building is to stand the test of time it must be constructed of materials that allow for this natural movement. Lime mortar is softer than stone or brick and therefore able to accommodate movement without cracking.

Lime mortar also has the advantage of being permeable. It allows the building to breathe by evaporating moisture from within the walls. Consequently, buildings constructed with lime mortar can stay dry on the inside without damp proofing.

Like a good wine, lime mortar improves with age and will last indefinitely as long as it is kept from drying out.

Interesting facts

Various ingredients were often added to lime mortar to improve its strength, durability and even colour.

  • Animal hair, usually from a goat, was added for extra strength and to minimise shrinking/cracking
  • Quartz was also used to minimise shrinking
  • Beer was added as it created bubbles which made the mortar more breathable
  • Oil made the mortar more waterproof
  • The blood of a strong animal, often an ox, was believed to strengthen anything made from lime mortar. It also coloured the mortar.

Last date edited: 18 September 2017