Why Proper Mortar Mixing Matters

Mortar is the glue that holds masonry together. Improperly mixed mortar leads to:

Weak joints that crack and crumble
Water infiltration through walls
Structural failure over time
Costly repairs and repointing

Master the mix, and your masonry work will last generations.

Understanding Mortar Types

ASTM Mortar Classifications

Type	Strength (PSI)	Best Uses
M	2,500+	Below-grade, foundations, retaining walls
S	1,800+	Structural walls, high wind/seismic areas
N	750+	General purpose, above-grade walls
O	350+	Non-load-bearing, interior walls
K	75+	Historic restoration, soft brick

When to Use Each Type

Type N (Most Common)

Residential brick veneer
Chimneys above roofline
Interior partitions
Moderate load applications

Type S (Strong)

Foundation walls
Below-grade masonry
High-wind regions
Structural reinforced walls

Type M (Maximum)

Retaining walls
Below-grade applications
Severe frost exposure
Heavy load-bearing

Pro tip: When in doubt, use Type S. It’s overkill for most residential but won’t cause problems. Using too weak a mortar is the real mistake.

Mortar Components

Portland Cement

Provides strength
Type I or II for most applications
Never use “plastic cement” (has additives)

Lime

Improves workability
Increases bond strength
Adds flexibility (reduces cracking)
Helps retain water during curing

Sand

Provides bulk and texture
Must be clean, well-graded
Masonry sand (fine) preferred
Never use beach sand (salt content)

Water

Clean, potable water only
Temperature affects set time
Most critical variable in mixing

Pre-Mixed vs. Job-Mixed Mortar

Pre-Mixed Bags (Type S, N)

Pros:

Consistent proportions
Convenient for small jobs
No measuring required

Cons:

More expensive per unit
Less control over workability
May have additives

Best for: DIYers, small projects, repairs

Job-Mixed (Custom Proportions)

Pros:

Lower material cost
Adjustable for conditions
Better for large quantities

Cons:

Requires accurate measuring
More knowledge needed
Potential for errors

Best for: Professionals, large projects

Standard Mix Proportions

Type N (General Purpose)

1 part Portland cement
1 part lime
6 parts sand

Type S (Structural)

1 part Portland cement
1/2 part lime
4.5 parts sand

Type M (Heavy Duty)

1 part Portland cement
1/4 part lime
3.5 parts sand

Measuring: Use consistent containers. A 5-gallon bucket works well.

Step-by-Step Mixing Process

Equipment Needed

Mortar mixer (rental) or wheelbarrow
Mixing hoe or drill with paddle
5-gallon buckets for measuring
Water source with hose
Mortar board or hawk
Clean sponge

Method 1: Mortar Mixer (Best for Large Jobs)

Add most of the water (about 2/3 of total)
Add half the sand while mixer runs
Add all cement and lime
Add remaining sand
Mix 3-5 minutes - no dry pockets
Add remaining water gradually
Mix until proper consistency (2-3 more minutes)

Method 2: Wheelbarrow/Hand Mixing

Dry mix first - Blend cement, lime, sand
Form a crater in center of dry mix
Add half the water to crater
Fold dry material into water from edges
Continue adding water gradually
Mix thoroughly - 10+ minutes by hand
Check consistency before using

Method 3: Pre-Mixed Bags

Empty bag into mixer or wheelbarrow
Add water gradually (see package directions)
Mix until uniform consistency
Let stand 5 minutes (slaking)
Remix briefly before use

The Perfect Consistency

Visual Indicators

Smooth, creamy texture (like peanut butter)
No dry lumps or pockets
Holds shape when peaked with trowel
Slides off trowel when shaken gently

The “Thumb” Test

Press thumb into mortar
Lift straight up
Mortar should stick briefly, then release
Impression should hold shape

The “Trowel” Test

Load trowel with mortar
Turn trowel upside down
Mortar should stick for 2-3 seconds
Should fall cleanly when shaken

What Wrong Looks Like

Too wet:

Runny, slumps immediately
Squishes out of joints
Weak when cured
Fix: Add more dry mix sparingly

Too dry:

Crumbly, falls apart
Won’t stick to units
Poor bond strength
Fix: Add small amounts of water

Not mixed enough:

Visible dry pockets
Inconsistent color
Variable strength
Fix: Continue mixing 2-3 more minutes

Working Time and Retemper

Working Time (Pot Life)

Normal conditions: 2-2.5 hours
Hot weather (above 90°F): 1-1.5 hours
Cold weather (below 40°F): 3-4 hours

Retempering (Adding Water)

As mortar stiffens from evaporation, you can add small amounts of water:

Acceptable:

Within first 2.5 hours
Small water additions only
Remix thoroughly
Once or twice maximum

Not acceptable:

After initial set begins
Large water additions
Multiple retemperings
Mortar that’s been standing 3+ hours

Rule: Never retemper mortar that’s begun to set. Discard it.

Calculating Mortar Quantities

Coverage Per Bag (80 lb)

Application	Coverage
Standard brick	30-35 bricks
Modular brick	40-50 bricks
8” concrete block	12-15 blocks
12” concrete block	8-10 blocks
Stone veneer	8-12 sq ft

Formula for Job-Mixed Mortar

Cubic feet of mortar = (sq ft of wall × joint thickness × 2) ÷ 144

Use our Masonry Calculator for accurate estimates.

Weather Considerations

Hot Weather (above 90°F)

Mix smaller batches
Keep materials shaded
Dampen bricks before laying
Work faster
Mist finished joints

Cold Weather (below 40°F)

Heat mixing water (not over 160°F)
Use heated sand
Cover work overnight
Consider accelerators
Never lay on frozen surfaces

Rain

Don’t mix mortar in rain
Cover fresh work immediately
Don’t resume until surfaces dry
Check joints next day

Colored Mortar

Adding Pigments

Use mortar-specific pigments only
Maximum 10% of cement weight
Add pigment to dry mix before water
Mix thoroughly for uniform color
Keep batches consistent

Color Matching Tips

Make test samples first
Let samples cure 28 days to see true color
Wet mortar is always darker than cured
Buy all pigment from same batch

Common Mistakes and Solutions

Mistake	Problem	Solution
Too much water	Weak, porous joints	Measure water carefully
Not enough mixing	Inconsistent strength	Mix minimum 5 minutes
Wrong mortar type	Cracks or too hard	Match to application
Dirty sand	Poor bond	Use clean masonry sand
Using old cement	Reduced strength	Check bag date, store dry
Retempering set mortar	Joint failure	Discard after 2.5 hours

Troubleshooting Mortar Problems

Joints Cracking

Causes:

Mortar too strong for brick
Insufficient curing
Structure settling

Fix: Use softer mortar type, ensure proper curing

Efflorescence (White Staining)

Causes:

Water migration through masonry
Salt content in materials

Fix: Improve drainage, use low-alkali cement

Poor Bond (Bricks Falling Off)

Causes:

Dusty brick surfaces
Mortar too dry
Temperature extremes

Fix: Dampen bricks, proper consistency, weather protection

Discoloration

Causes:

Inconsistent batches
Varying water content
Different sand sources

Fix: Consistent measuring, same material sources

Mortar Storage Tips

Unopened Bags

Store off ground on pallets
Keep dry - no moisture exposure
Use within 6 months
First in, first out

Mixed Mortar

Use within 2.5 hours
Don’t store overnight
Cover with damp burlap while working
Never freeze

Calculate Your Masonry Materials

Ready to estimate your project? Use our free calculators:

Masonry Calculator - For brick and block walls
Concrete Block Calculator - For CMU walls

Pro Tip: Keep detailed notes on your mortar mix for each job - water amounts, weather conditions, and results. This helps you replicate good batches and avoid repeating mistakes. Many professional masons keep a mixing log for exactly this reason.