# What is bastard mortar?
**Bastard mortar (also called compo mortar or gauged mortar) is a bricklaying mortar consisting of a mixture of cement, lime, sand, and water.** The name ‘bastard’ refers to the fact that it is a hybrid between pure cement mortar and pure lime mortar, combining the advantages of both binders.
## Composition
A standard bastard mortar contains:
– **Cement** — provides strength and water resistance
– **Lime** — improves workability and flexibility
– **Sand** — the filler material (usually bricklaying sand, grain size 0–2 mm)
– **Water** — activates the binder
A commonly used mix ratio is 1 part cement, 1 part lime, and 6 parts sand.
## Properties
– **Good workability** — the lime makes the mortar smooth and easy to work
– **Moderate strength** — stronger than pure lime mortar, but weaker than cement mortar
– **Slightly elastic** — can accommodate small movements in the masonry without cracking
– **Vapour-open** — allows moisture to escape from the masonry
## Application
– **Bricklaying** — for internal and external walls
– **Repointing** — when re-jointing existing masonry
– **Rendering** — as a base coat (scratch coat)
### When not to use bastard mortar
For structural masonry under heavy loads or work below the water table, cement mortar is the better choice due to its higher strength and water resistance.
## Related terms
– Mortar
– Bricklaying
– Pointing
– Bond pattern
– Joint
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