What is Mortar? Definition, Qualities, and Applications

What is Mortar?

Mortar is a building material that is a combination of cement, fine sand, lime, and water. Mortar is most often used to bind bricks, stones, or other building units together. It acts as a glue that provides the structural integrity and strength that is essential when combining small units together. Mortar helps these units create a strong and protective barrier and form them into unified structures that can withstand the test of time.

Composition of Mortar

The main component of mortar is cement, usually ordinary Portland cement, which is a combination of limestone and clay. Manufacturers add sand to improve the workability of the mixture and provide it with some bulk. The hydration process begins when they add water to the mix. Hydration is a chemical reaction that helps it to harden and create the bond which provides the adhesive qualities.

While ordinary Portland cement is the main binder in mortar, different types of mortars use other binders including polymers, hydraulic lime, and pozzolanic materials like volcanic ash. Builders choose different types of mortars based on their qualities and the application for which they are intended.

Builders typically mix the mortar on-site in order to tailor the mixture for different applications and depending on the desired strength and consistency. They apply it between bricks and stones to create a barrier between the units and make them stick together. The mortar will dry and harden over time in a process called curing. Once it cures, it creates a durable and weather-resistant barrier.

For non-professionals, there is also premixed mortar. This mortar blend eliminates the need for measuring and mixing. There are different types of premixed mortars that work for a wide range of applications. These blends are convenient and have a consistent quality.

Qualities of Mortar

Mortar possesses qualities that contribute to its effectiveness and functionality. These are the qualities that masons look for when considering which type of mortar to use for specific jobs.


Mortar should have good workability, which means that it should be easy to manipulate, handle, and place for a specific task. Mason should be pliable enough to be spread and shaped without excessive effort.


Mortar must adhere well to the surface of the material which it is binding together. The bond that it forms with the building units must survive separation and dislocation over time to ensure the strength of the structure or building.


Mortar should have sufficient strength to withstand the loads that are placed upon it. The composition, curing process, and ratio of cement to sand help to determine the strength of a particular type of mortar. Different applications require different strength mortars.


The optimal mortar will be able to withstand various environmental conditions and still maintain its integrity over an extended time. It should be able to stand up to weathering, freeze-thaw cycles, chemical reactions, and other detrimental factors.

Water Resistance

Mortar should be able to have some resistance to water to withstand moisture penetration. This is vital in preserving the structural integrity of any outdoor building that faces exposure to rain, humidity, and other forms of moisture.

Shrinkage Control

Mortar should minimize the amount of shrinkage that happens during the curing process to avoid cracking and maintain its strength. Adequate curing time and proper curing methods will help mortar to withstand shrinkage.

Color and Aesthetics

Manufacturers can formulate mortar in different colors and textures to enhance the visual appeal of the structure.

Uses of Mortar

Mortar has numerous applications in construction and masonry work.

  • Bricklaying – Masons use mortar to bond bricks together for the construction of walls, buildings, and other brickwork structures. Mortar binds the bricks together to create a strong and durable unit.
  • Stone Masonry – Mortar is used to join and secure stones of various types and shapes into a cohesive structure and enhance the aesthetics of the stone.
  • Blockwork – Builders use mortar to connect concrete blocks or hollow blocks in the creation of foundation structures, partitions, and load-bearing walls. Mortar helps provide proper alignment, strength, and durability of the structure.
  • Plastering – Mortar is used for plastering interior and exterior walls to decrease their permeability and provide a smooth and even finish to walls and ceilings. Plaster helps to level uneven surfaces, fill gaps, and enhance the look of the surface.
  • Repointing – Pointing refers to the gridwork of mortar between bricks. Masons use mortar for pointing, but because mortar is the weakest part of the brick wall, it deteriorates over time and needs to be repaired. Repointing refers to the process of removing old mortar and replacing it with new mortar.
  • Tile Installation – A special variety of mortar, called thin-set mortar, is used to adhere and connect tiles on walls, counters, and floors. The mortar helps create a bond between tiles and affix them to the substrate.
  • Chimney Construction – Mortar is vital in creating tall and narrow structures that conduct heat and smoke away from the fireplace. Mortar can withstand the intense heat and gases produced by fireplaces and heating systems.
  • Waterproofing – Some mortars contain additives or are specially formulated to create resistance to water. Builders use mortar for waterproofing basements, creating pools, and other structures that are exposed to water.

Methods for Applying Mortar

Builders, masons, and DIYers use various methods to apply mortar to their designs. The application method depends on the type of mortar and the structure.

Trowel Method

The trowel method is the most common method for applying mortar. For this method, a builder or mason will use a metal tool called a trowel to scoop up the mortar from a mortarboard and then spread it onto the surface or between the mortar units. Masons use the flat side of the trowel to spread and shape the mortar.

Pointing Method

Pointing is the process of repairing or filling mortar joints in masonry structures. For this technique, bricklayers use a specialized tool called a pointing trowel. They use this tool to press mortar into the joint and smooth it to create a cohesive look with the existing mortar.

Bagging Method

Bagging is a common application method for vertical or overhead surfaces. For this technique, mortar is placed into a bag and then squeezed to extrude the mortar through a small opening. This method allows for highly controlled application. Masons might later use a trowel to smooth the mortar or shape it to fit the space.

Spraying Method

For large-scale projects or particular applications, mortar is applied using a mortar sprayer or mortar pump. This method involves spraying the mortar onto a surface using compressed air or a mechanical pump. Spraying allows for quick, efficient, and even coverage. This method is common for stucco or plaster applications.

Buttering Method

The buttering method is common for applying mortar in tile projects. This method involves applying a thin layer of mortar, called a butter coat, to the back of the tiles using a trowel. This ensures a strong bond between the tile and the substrate.