Module 7 · Proportionate Remediation
7.4 Conservation-Compatible Repair
9 min read
A repair to an older building can conserve it or slowly destroy it, and the difference is usually a choice of material made without much thought. Cement where lime belongs, a plastic paint where a permeable one belongs, a tanking system where drying belongs: each looks like a competent modern repair and each removes the building's ability to manage moisture the way it was designed to.
Learning objectives
By the end of this lesson you will be able to:
- Select materials compatible with the building's moisture strategy.
- Apply the principles of reversibility and sacrificial repair.
- Specify a plaster system for a salt-contaminated wall.
- Recognise where conservation constraints change what is permissible.
Key terms
- Compatibility
- A repair material's permeability, strength and movement behaviour matching the fabric it joins, so it does not concentrate stress or moisture in the original material.
- Sacrificial
- A repair intended to take the damage and be renewed, protecting the irreplaceable fabric behind it. Lime pointing is the standard example.
- Reversibility
- The ability to remove a repair later without damaging what it was applied to. A conservation principle with a practical benefit — it keeps future options open.
- Salt-resistant render
- A plaster system designed to keep contaminated substrate salts away from the decorated surface, either by resisting transport or by holding crystallisation within a sacrificial layer.
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