Mortar Mix & Bag Estimator

For standard modular clay bricks with standard 3/8-inch (10 mm) mortar joints, you need approximately 28 to 30 bags of 80 lb pre-mixed mortar (or 38 bags of 60 lb mix, or 52 to 55 bags of 20 kg mix), which accounts for brick core extrusion and 10% trowel drop waste. If mixing raw materials on site at a 1:1:6 Type N ratio, you only need 3 bags (94 lb) of pure Portland cement, plus 3 bags (50 lb) of hydrated lime and ~0.8 cu yds (1 ton) of masonry sand.

Laying standard 8×8×16 concrete CMU blocks (face-shell bedding with 3/8" joints) requires approximately 3 to 3.5 bags of 80 lb pre-mix mortar (or 4 to 5 bags of 60 lb mix, or 6 bags of 20 kg mix) per 100 blocks.

Type S mortar has high compressive strength (1,800 PSI) and superior flexural bond, required for exterior retaining walls, foundations, below-grade masonry, and structural block. Type N mortar (750 PSI) is medium strength, ideal for above-grade exterior brick veneer, interior non-load-bearing walls, and chimneys.

The standard architectural mortar joint thickness for bricks and concrete masonry units (CMU) is 3/8 inch (10 mm). Joints thinner than 1/4" or thicker than 1/2" weaken structural bonding.

A standard Type S jobsite mix recipe by volume is 1 part Portland cement, 1/2 part hydrated lime (Type S), and 4 to 4.5 parts clean, damp masonry sand (ASTM C144). Add clean potable water until a smooth, buttery consistency is achieved.

No. Concrete contains coarse gravel aggregate (1/2" to 3/4" rock) that prevents thin 3/8" bed joints and lacks the workability, stickiness, and lime content required to bond bricks without crumbling.

Add approximately 4.5 to 5 quarts of clean water per 80 lb bag. Pour 3/4 of the water into the mixer first, add the dry mortar, and blend in the remaining water gradually until it clings to an overturned trowel.

Mixed mortar has a pot life of approximately 1.5 to 2 hours. In warm, dry weather, you can "retemper" the mortar by sprinkling light water to replace evaporative moisture within the first 90 minutes. Never retemper mortar that has begun chemical hydration.

Crumbling joints occur when dry bricks suck water out of the mortar before hydration completes, when the mortar freezes before curing, or when mixed with excessive water. Wet porous bricks lightly before laying in hot weather.

Unopened dry mortar stored in a dry, covered room on pallets has a shelf life of 6 to 12 months. If the mix contains hardened lumps that cannot be crushed by hand, the cement has hydrated from atmospheric moisture and should be discarded.

Tool or strike the joints once the mix feels like firm modeling clay—hard enough to leave a clean thumbprint without sticking to your skin (usually 30 to 60 minutes after placing the brick). Doing it too soon smears wet gray paste across the brick face; waiting too long makes it too hard to shape cleanly.

Wait an hour or two for drips to firm up until crumbly, then scrape or flick them off with a piece of scrap wood, a trowel edge, or a stiff nylon brush. Never use a wet sponge (it rubs cement paste deep into the brick pores) or wire brushes (metal leaves rust marks). For leftover stains or haze, let the wall cure for two weeks, then wash it with a masonry brick cleaner.

Only if the dry bricks drink water quickly (high suction). Splash a few drops of water on a brick; if it soaks in within a minute, lightly spray your brick pile with a garden hose an hour before building so they are damp but not dripping wet. If a thirsty, bone-dry brick touches wet mortar, it sucks out the water immediately and ruins the bond, causing joints to crumble.

Mix only half a bag (about one 5-gallon bucket) at a time for DIY work. Mortar begins stiffening and setting in about 60 to 90 minutes. Unless you have a helper laying bricks rapidly, mixing a whole 80 lb bag at once means half of it will harden into a solid rock inside your tub before you can use it.

No. Rain washes away the sticky cement binder, weakens the joints, and causes efflorescence (ugly white chalky salt stains bleeding through the brick later). If it starts to rain, stop immediately and cover both your mixing tub and your fresh wall with a waterproof plastic tarp.