- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 04 Nov 2018
To help develop this article, click ‘Edit this article’ above.
Mortar is one of the oldest building materials, enabling large structures to be constructed from small, easy-to-handle components. It was used by the Romans, Greeks and Egyptians, and the oldest example may date back as far as 10,000 years in Israel (ref. Mortar Industry Association).
It is composed from a mixture of a fine aggregate (typically sand), a binder (typically cement, but sometimes lime or a combination of lime and cement) and water. This combination creates a paste that is used in masonry construction as a bedding and adhesive to bind and fill the gaps between adjacent blocks of brick, concrete or stone.
Mortar is applied as a thick paste which sets hard as it cures. It creates a tight seal between bricks and blocks to prevent air and moisture entering into the construction. It can compensate for variations in brick or block size to produce an aesthetically-pleasing and structurally-sound construction. Generally, it is structurally weaker than the blocks or bricks it bonds, creating a sacrificial layer that is more easily repaired than defects would be in the bricks or blocks themselves.
- Wet ready-to-use mortar that requires no further mixing.
- Dry ready-to-use mortar which requires the addition of water.
Factory-produced mortar is made under tightly-controlled conditions and provides:
- Consistent quality, colour and strength.
- Reduced mixing and labour costs.
- Reduced wastage.
- Guaranteed specification.
- Improved site health and safety.
The profile of mortar joints (pointing) can be varied depending on exposure or to create a specific visual effect. The most common profiles are; flush (rag joint), bucket handle, weather struck, weather struck and cut, and recessed.
A wide range of colours are available to match or contrast with the surrounding bricks or blocks, or to match existing mortar. Pigments are specified according to BS EN 12878:2014 Pigments for the colouring of building materials based on cement and/or lime. Specifications and methods of test.
A range of admixtures can be included in mortar, such as plasticisers, bonding agents, and waterproofing. These can be specified according to BS EN 934-3:2009+A1:2012 Admixtures for concrete, mortar and grout. Admixtures for masonry mortar. Definitions, requirements, conformity and marking and labelling.
Mortar must have good workability to ensure there are no air pockets which might prevent proper bonding. Plasticisers can improve workability by entraining very small air bubbles in the mix. Alternatively, the addition of lime can improve the workability of mortar.
Where porous bricks or blocks are being laid, the mortar may dry quickly, preventing proper levelling and so preventing a good bond from being formed. This can be countered by laying shorter lengths or by limited wetting.
 Find out more
 Related articles on Designing Buildings Wiki
- Binding agent.
- Defects in brickwork.
- Defects in stonework.
- Hot-mixed mortars: the new lime revival.
- Lime mortar.
- Mortar analysis for specifiers.
- Parge coat.
- Types of mortar.
- Which way up should you lay a brick?
 External references
- Mortar Industry Association (MIA).
Featured articles and news
An artist finds ruined and decaying buildings a source of inspiration for his work. Book review.
When is there a right to light, and what happens if it is obstructed?
What would the nationalisation of economic infrastructure mean for GB?
A new guide to improving value by reducing design error.
We've reached 80,000 page views a day and 10,000 registered users. Why not join them?
A masterplan is a framework within which a location is encouraged to develop or change. Read our introductory article.
New consultation announced on a specialist Housing Court to settle landlord-tenant disputes.
ICE responds to a transport consultation advising the government to make decisions enabling more inclusive cities.
BRE and Loughborough University complete first phase refurbishment of demonstration home.
If you’re a great writer and have practical experience of the construction industry, it could be you.
Frustrated by long documents or technical jargon? Put off by sign-up forms or costs? Take this 5 min survey to help improve construction knowledge.