Mortar
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.
Mortar is generally very durable and has a typical lifespan of between 20-30 years, after which repairs (or repointing) can be necessary to fill cracks or gaps that may begin to appear.
Mortar may be provided in its component parts and mixed on site, or factory-mixed. The two main types of factory-produced mortar are:
- 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.
For the different types of mortar, see Types of mortar.
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.
[edit] Related articles on Designing Buildings
- Cement.
- Cement mortar.
- Defects in brickwork.
- Defects in stonework.
- Dry hydrate lime mortar.
- Efflorescence.
- Gauged mortar.
- Hot-mixed mortars: the new lime revival.
- Hungry joints.
- Lime mortar.
- Lime putty mortar.
- Mortar analysis for specifiers.
- Rendering.
- Repointing.
- Spalling.
- Stucco.
- Technical Paper 32 – A Data Driven Approach to Understanding Historic Mortars in Scotland.
- Textile-reinforced mortars TRM.
- Types of mortar.
- Which way up should you lay a brick?
[edit] External references
- Mortar Industry Association (MIA).
Featured articles and news
OpenUSD possibilities: Look before you leap
Being ready for the OpenUSD solutions set to transform architecture and design.
Global Asbestos Awareness Week 2025
Highlighting the continuing threat to trades persons.
Retrofit of Buildings, a CIOB Technical Publication
Now available in Arabic and Chinese aswell as English.
The context, schemes, standards, roles and relevance of the Building Safety Act.
Retrofit 25 – What's Stopping Us?
Exhibition Opens at The Building Centre.
Types of work to existing buildings
A simple circular economy wiki breakdown with further links.
A threat to the creativity that makes London special.
How can digital twins boost profitability within construction?
The smart construction dashboard, as-built data and site changes forming an accurate digital twin.
Unlocking surplus public defence land and more to speed up the delivery of housing.
The Planning and Infrastructure Bill
An outline of the bill with a mix of reactions on potential impacts from IHBC, CIEEM, CIC, ACE and EIC.
Farnborough College Unveils its Half-house for Sustainable Construction Training.
Spring Statement 2025 with reactions from industry
Confirming previously announced funding, and welfare changes amid adjusted growth forecast.
Scottish Government responds to Grenfell report
As fund for unsafe cladding assessments is launched.
CLC and BSR process map for HRB approvals
One of the initial outputs of their weekly BSR meetings.
Building Safety Levy technical consultation response
Details of the planned levy now due in 2026.
Great British Energy install solar on school and NHS sites
200 schools and 200 NHS sites to get solar systems, as first project of the newly formed government initiative.
600 million for 60,000 more skilled construction workers
Announced by Treasury ahead of the Spring Statement.