Mortar is the material that sticks two masonry units together and prevents water from getting into the wall — it is what you see between bricks. Since mortar plays such an important role in masonry construction, selecting the correct type of mortar is vital.

As discussed in our article Mortar vs. Grout, mortar sticks and grout fills. We have a separate article that covers masonry grout, which is generally used to fill the cavities of concrete block.

Mortar is also used in ceramic tile construction, which we discuss at Thin-Set Tile Mortar Types.

The ingredients used in mortar are water, cement, lime, and fine aggregates like sand. The proportions of the ingredients vary based on the performance properties required in the final product (bonding strength, compressive strength, flexural strength).