Type S Mortar Mix: Complete Guide for Homeowners

Pick up the wrong bag of mortar at Home Depot and you will either spend twice on materials or watch your brick wall crack before the second winter. Type S mortar mix is the stronger of the two most common residential mortars — rated at a minimum 1,800 PSI compressive strength versus 750 PSI for Type N. That extra strength makes Type S the right choice for load-bearing walls, below-grade work, and anywhere the structure faces wind or freeze-thaw cycles.

What Makes Type S Different

ASTM C270 is the US standard that defines mortar types. The main difference between grades is the ratio of portland cement to hydrated lime. Type S mortar contains roughly 2 parts portland cement to 1 part hydrated lime to 9 parts sand. Type N is about 1:1:6. That higher cement content gives Type S greater compressive strength, better freeze-thaw durability, and higher bond strength — at the cost of slightly reduced workability on the trowel.

Hydrated lime is not the same as quicklime or garden lime. It is a specific construction-grade hydrated lime (Type S or Type SA) certified to ASTM C207.

When to Use Type S

Type S is specified by most local building codes for:

• Load-bearing walls (exterior brick veneer, structural CMU)
• Foundation walls and anything below grade
• Retaining walls under 4 feet tall (taller walls typically need engineered design)
• Chimney repair and repointing
• Exterior stone veneer where wind loads exceed 90 mph
• Manholes, catch basins, and sewer structures
• Brick walkways and patios subject to freeze-thaw cycles

Always check local code — some jurisdictions require Type M (2,500 PSI) for certain applications, which is cement-heavier still.

When NOT to Use Type S

Type S is overkill — and sometimes problematic — for:

• Interior non-load-bearing walls (Type N is cheaper and easier to work with)
• Historic brick repointing on pre-1920 buildings (Type S is too hard and will spall the softer historic brick)
• Glass block walls (requires specialty mortar)
• Refractory work around fireplaces (requires fire-rated mortar)

The historic brick issue is the one most DIYers miss. Old soft brick is designed to flex and breathe; modern Type S mortar is harder than the brick itself and forces the brick face to take the movement, causing spalling.

Mixing Ratios for Bag and Batch

Pre-mixed Type S comes in 60 or 80-pound bags at $8 to $14 each. Quikrete Type S, Sakrete Type S, and Spec Mix Type S are the three most common brands. For small jobs, buy the bag.

For larger batches from raw materials:

• 2 parts portland cement (Type I or Type II)
• 1 part hydrated lime (Type S hydrated lime per ASTM C207)
• 9 parts clean masonry sand
• Water to achieve the right plasticity (about 5.5 gallons per 80-pound bag of cement)

Measure by volume, not weight. A 5-gallon bucket makes a convenient measure on small jobs.

How to Mix Type S Properly

Follow these steps whether using bagged or site-mixed:

1. Put roughly 2/3 of the required water in the mixer or wheelbarrow first
2. Add dry materials gradually while mixing
3. Mix for 3 to 5 minutes total — not more, not less
4. Add remaining water to achieve trowel consistency: holds its shape, falls off the trowel when shaken
5. Let mix rest (slake) for 3 minutes, then mix briefly again
6. Use within 90 minutes on temperate days, less on hot or windy days

Never “temper” mortar by adding more water after it starts to set — this dramatically weakens the final strength. If a batch stiffens too fast, discard it and mix fresh.

Working Time and Temperature

Temperature affects both workability and cure:

• 40°F minimum: below this, use hot water and heated materials
• 50 to 70°F: ideal working range, 90-minute pot life
• 80 to 90°F: pot life drops to 60 minutes; mist brick to control absorption
• Above 90°F: work in shade, reduce pot life to 45 minutes

Newly placed mortar should be kept damp for 48 to 72 hours to achieve design strength. Mist with water once or twice a day in hot weather, cover with plastic in freezing conditions.

Coverage and Quantity Estimation

For planning materials:

• An 80-pound bag of Type S mortar covers approximately 30 to 35 standard (2-1/4 x 8 inch) bricks with 3/8-inch joints
• A standard pallet of 500 bricks needs about 15 to 17 bags of mortar
• A 100 sq ft brick wall needs roughly 9 bags of mortar
• For block work, one bag fills about 25 cores in CMU

Round up by 10 to 15%. Running short mid-wall and needing to drive to the store again costs more than a few spare bags.

Common Pitfalls With Type S

Avoid these mistakes:

1. Using Type S on soft historic brick (spalls the brick face)
2. Adding water after mortar starts to set (weakens strength by 30 to 50%)
3. Mixing on concrete and letting mortar sit directly on the slab (slab absorbs water, drying the mix)
4. Skipping the slaking step (reduces final bond strength)
5. Mixing more than you can use in 90 minutes
6. Using masonry sand with organic matter (reduces strength and bond)
7. Applying to dusty, dirty, or wet-saturated substrates

Type S vs Type N vs Type M

Quick comparison:

• Type M: 2,500 PSI. Heavy-duty foundations, retaining walls over 4 ft, commercial
• Type S: 1,800 PSI. Most residential exterior and structural work
• Type N: 750 PSI. Interior and above-grade non-load-bearing
• Type O: 350 PSI. Historic repointing, non-structural

When in doubt between S and N, most contractors default to S for anything touching weather or holding weight.

Tools and Supplies for Application

A basic mortar job needs:

• Brick trowel (10 or 11-inch) and pointing trowel ($18 and $14)
• Mortar pan or wheelbarrow
• Paddle mixer drill attachment or electric mortar mixer
• Jointing tool matching desired joint profile (concave, V, grapevine, etc.)
• Mason’s level (4-ft and 2-ft sizes)
• Mason’s line and pins for alignment
• PPE: gloves, eye protection, long sleeves (mortar is caustic)

Testing and Quality Control

For code-compliant commercial work, ASTM C780 field testing of mortar cubes is often required. For homeowner projects, the slump test is enough: scoop mortar with a trowel, tilt 90 degrees, and it should cling without falling. If it slides off, too wet. If it cracks and crumbles, too dry.

Spec the right mix, measure the right proportions, and apply in the right conditions, and type s mortar mix will outlast the structure it holds together — typical design life on a properly laid Type S masonry wall is 75 to 100 years.