Mortar is not the same as concrete. It's designed to bond masonry units together, fill gaps, and create a weather-tight seal.
Mortar Types (ASTM C270)
- Type M (2,500 psi): Below-grade, foundations, retaining walls
- Type S (1,800 psi): Structural, exterior walls, severe weather
- Type N (750 psi): General purpose, above-grade (most common)
- Type O (350 psi): Interior, non-load-bearing
Mix Ratio (Type N)
1 part cement : 1 part lime : 5–6 parts sand. Add water until workable consistency.
Mortar vs. Grout vs. Concrete
These three are often confused: mortar bonds masonry units together and doesn't need to flow (thick, sticky). Grout fills gaps and voids and is mixed thinner so it flows into small spaces (like between tiles or into block cores). Concrete contains coarse aggregate (gravel) for structural strength and is used for slabs, footings, and foundations — none of the three are interchangeable despite looking similar when wet.
Mortar Joint Thickness
Standard mortar joints run 3/8" thick for most brick and block work — thinner joints (1/8"–1/4") are used for "thin-brick" veneer systems, while thicker joints can be used to correct for slightly irregular stone in masonry work.