The difference in short
Short answer: Lime mortar is softer and more breathable, while cement mortar is harder and denser. The right choice depends on the structure, the substrate, and how the wall needs to handle moisture and movement.
A simple repair rule: your patch should be compatible with the existing materials—otherwise you risk new cracking or trapped moisture.
When is lime mortar suitable?
Lime mortar is often used in traditional masonry and renders where breathability is important. It can help the wall handle moisture without trapping it.
Need lime systems in practice? See lime plaster / lime mortar.
When is cement mortar suitable?
Cement mortar is commonly used in modern construction where the substrate and system are designed for it. The key is matching the mortar to both the masonry material and the wall’s function.
Risks of the wrong mortar
Using the wrong mortar can cause cracking, render delamination, or trapped moisture that leads to long-term damage. A common issue is a very hard cement repair on a softer lime-based structure—then stresses and moisture end up in the wrong place.
How do you choose the right one?
We typically look at:
- masonry/render type and earlier repairs
- crack patterns, delamination and movement
- moisture exposure and weathering
- the finish and maintenance you want
After a site visit, we recommend a compatible mortar/render system for your structure.
Repairs and maintenance
When repairing, the mortar must be compatible with the existing material. This is key for durability.
How it works
We assess on site and recommend the right method for your masonry or facade. Within our service areas, we offer free site visits.
Book an assessment
Describe your masonry (photos help) and we’ll get back with next steps. Contact us here. Read more about us on the homepage.
