Mortar Calculator

Type N is a medium-strength mix at roughly 750 psi and is the default for above-grade, non-loadbearing work: brick veneer, soft or historic masonry, and chimneys above the roofline. It is deliberately weaker than the units so the joint, not the brick, takes the movement. Type S runs about 1,800 psi and is specified at or below grade — foundations, retaining walls, loadbearing block, and stone or paver setting beds. If a drawing or your local code names a type, use that type. Stronger is not automatically better; hard mortar will spall soft brick. Treat the quantities here as a planning estimate — on a loadbearing, below-grade, or retaining wall the mortar type and joint detail are set by local code and by the engineer or licensed mason on the job, not by a calculator.

Pre-mixed 80 lb bags are the right call for anything under a few hundred units: consistent proportions, no sand pile in the driveway, and about $6 to $10 a bag. Site mixing gets much cheaper at volume. A typical Type S recipe is 1 part portland, 1/2 part hydrated lime, and 4 1/2 parts damp masonry sand by volume. A long-standing shop benchmark is roughly 1 cubic yard of sand plus 7 bags of masonry cement per 1,000 brick — a more generous allowance than the bag figure here, because bulk mixing assumes heavier droppings.

Mortar volume scales almost directly with joint thickness, since you are filling a bed and a head joint on every unit. Moving from a 3/8-inch joint to a 1/2-inch joint adds roughly 25 to 35 percent to consumption, which is why the wide-joint option applies a 1.25 multiplier. It also changes layout: 3/8 inch is exactly what makes modular brick land on 8-inch coursing and block on its 8 × 16 module, so widening joints throws off your coursing over a long wall. To make up height, spread the difference across several bed joints rather than running one fat one.

Sealed, kept dry, and stored off the ground, bagged mortar mix is generally good for about a year. Most manufacturers print a date, and any lump you cannot crush by hand means the bag has picked up moisture and should be thrown out. Mixed mortar has a board life of roughly 2 1/2 hours in mild weather and less in heat or wind. You can retemper once within that window by adding a small amount of water and remixing, but never retemper mortar that has started to set — the strength loss is permanent and the bond will fail.

At about 45 bricks per 80 lb bag with 3/8-inch joints, 1,000 standard modular bricks take roughly 22 bags before waste and 25 bags with a 10% allowance — call it $150 to $250 in material. Block is a heavier feeder per unit: 1,000 standard 8 × 8 × 16 blocks at 28 per bag come to about 36 bags before waste, 40 with waste. Both figures assume face-shell bedding on block and normal droppings. Full-bed first courses, corners, and bond beams use more, so keep a couple of spare bags on the pallet.