Lime Mortar
A traditional mortar using lime rather than cement as the binder, setting slowly by carbonation and remaining softer and more vapour-permeable than cement mortar.
On an actual building
On historic buildings it is sacrificial by design — softer than the masonry so damage concentrates in the mortar rather than the stone or brick. Repointing in cement reverses that relationship.
What we most often have to correct
That cement is a stronger, better version. Its hardness and impermeability are precisely what damages historic fabric.
Terms that come up alongside this one
- Breathability (Vapour Permeability)
The ability of a material to let water vapour pass through it while still resisting liquid water..
- Silane-Siloxane Treatment
A penetrating water repellent that lines the pores of masonry and concrete without filling them, leaving the surface visually unchanged..
- Heritage Restoration
Repair of historic buildings using materials and techniques compatible with the original fabric, favouring breathable, reversible interventions..
Lime Mortar — questions we get asked
What does lime mortar mean in waterproofing?
A traditional mortar using lime rather than cement as the binder, setting slowly by carbonation and remaining softer and more vapour-permeable than cement mortar.
Why does lime mortar matter on a real project?
On historic buildings it is sacrificial by design — softer than the masonry so damage concentrates in the mortar rather than the stone or brick. Repointing in cement reverses that relationship.
What do people commonly get wrong about lime mortar?
That cement is a stronger, better version. Its hardness and impermeability are precisely what damages historic fabric.
Have a building showing this?
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