Introduction
Water ingress is a major factor in the upkeep of heritage properties. We regularly perform corrective works caused by the inappropriate use of modern materials (commonly by non-specialist trades people).
In the recent past, this Grade II Listed Hall in Lancashire had been inappropriately faced with cement mortar. The first floor had water ingress issues, therefore requiring a priority package of works which included the repointing of the first floor level.
Cover Photograph
The cover photograph was taken a few months after we repointed the first floor with lime mortar.
Note the obvious colour difference between the first and ground floors.
The lighter stone is lime pointed, and demonstrates that moisture can evaporate through the porous lime.
The darker ground floor stone remains pointed in modern cement, therefore moisture has been trapped and is affecting the stone.
Cement (non-permeable, hard, modern)
Cement mortar is a non-permeable material; Moisture can not readily evaporate through cement. Instead, moisture will try to penetrate the stone or brick as the next most available porous route.
This leaves masonry vulnerable to erosion and frost damage. The results can be crumbling ‘blown’ brickwork faces, or stone faces shearing off. Internal damp can be an early indicator.
Furthermore, cement sets harder than masonry. The edges of stone or brick will be under pressure from the inflexible cement mortar. Consequently, over time this can cause cracks allowing rain water to penetrate.
Cementituous render performs similarly to cementituous mortar.
Lime (permeable, flexible, traditional)
Lime is a permeable material; Moisture can readily evaporate through lime mortar. As a result water does not have to penetrate masonry to evaporate, allowing the masonry to maintain its integrity.
Furthermore, lime is a relatively flexible material which acts as a softer weather course between the hard masonry.
Lime is a traditional material, used when ‘period properties’ were built. The mixing and application of lime requires knowledge and skill to achieve its potential.
Lime render performs similarly to lime mortar.
Final Thoughts
In summary, Lime mortar will provide protection to your heritage building for a significant time if correctly applied by experienced and skilled craftsmen.
We assess each building upon its requirements and the circumstances of you, the Custodian. Previously, we have repointed homes in multiple phases – such as each elevation. This can sometimes be for priority, co-ordination or financial purposes. Patch repointing may be suitable for short term maintenance rather than repointing a full elevation. We happily recommend and discuss short and long-term options.
