How to Mix Mortar

Choose whether to use a mortar mix, or make your own mortar from scratch using Portland cement, fine masonry sand and clean tap water.

For larger jobs that might require multiple mortar batches, using a mortar mix may can ensure that the mortar has a consistent strength and appearance. Check manufacturer’s instructions as not all mix ratios or mixing times are the same. Different types of mortar mix have different strengths to withstand compressive loads.

If you’re doing a smaller job or want to save money, make the mortar from scratch.

• Begin by dry mixing the cement and sand.
  Use a separate mixing container for the dry components. The standard mortar mixing ratio is one part Portland cement to three parts sand. This varies depending on the type of mortar you need for your job.
• Add the sand to the concrete and use a mortar trowel or hoe to fold them together. Ensure the concrete and sand are completely mixed.
• Some types of mortar include hydrated lime in the dry mix. This makes the mortar more workable during application and more waterproof after it sets. If you want to include lime with mix made from scratch, use it to replace about 10% of the cement.

Avoid inhaling particles from the mix and keep them off your eyes or skin. Wear safety goggles, work gloves, long sleeves and a respirator mask. Mix the mortar outdoors if possible, and ensure that the wind is blowing away from you.

Pro Tip: Before adding the sand, sift it through a 1/4-inch wire screen to filter out any bits of stone that will be too large or coarse for the mortar.

Mixing mortar in a bucket or wheelbarrow is relatively easy, but renting a mortar mixer may be more convenient for large jobs.

• Determine the amount of water you need. The amounts can vary depending on the type of job, the level of moisture in the sand and even the weather. Consider one part water to three or four parts mix as a starting point. Add additional water as needed if the mix is too dry.
• When mixing mortar in a bucket, begin by adding about 3/4 of the water. Adding the water first reduces the chance the dry concrete or mortar mix will get stuck to the bottom of the bucket. Adding water first also reduces airborne dust.
• Gradually stir in the mix and the remaining water.
• Use a trowel or paddle to turn the mortar mix by hand. This can take five to 10 minutes.
• To mix the mortar more quickly and easily, use a paddle mixer or a power drill with a paddle attachment. Run the drill at a low rate per minute until the mix is thoroughly blended.
• Blend the mix until no visible water puddles or dry sections remain.
• Even if the mortar seems properly blended, keep stirring for at least two additional minutes to ensure a smooth blend.
• If the mortar seems too dry, add water as needed in small amounts. It’s better to add too little water at a time than too much.

Mortar mixers use rotating paddles in a stationary drum. Cement mixers can also be used to mix mortar, but the rotating drum can be more effective with concrete’s heavy aggregate. Mortar mixers are more effective with finer aggregates.

Pro Tip: If you mix mortar in a wheelbarrow, take extra care adding the mix. The shorter sides mean there’s a greater chance that water can splash out.

“Slaking” is a step that allows the mortar powders to hydrate, ensuring that the chemical bonding agents will activate and the building or repair materials will adhere.

• Immediately after mixing the mortar, allow it to sit and rest, or “slake,” for 10 minutes.
• After slaking, stir the mortar for about 5 additional minutes.
• Do not add water after the mortar has slaked, as it can significantly weaken the mixture.

Properly mixed mortar ready for use should have a consistency comparable to thick peanut butter. Test its thickness by seeing how it adheres to the trowel or mixing paddle.

• Scoop some of the mortar onto the tool and tip the tool 90 degrees.
• If it falls off immediately, the mix is too thin.
• If the mortar sample clings to the tool, it should be ready.

Once mixed, the mortar in the bucket should be workable for approximately 90-120 minutes. This is called the “pot life” of the mortar. Avoid mixing more mortar than you can apply in two hours as the remainder will become too dry to use. One person can generally apply about one cubic foot of mortar in 90 minutes.

While mortar becomes unworkable in two hours, it may need 24-48 hours to fully dry once applied.

When using a mortar mix for tile, choose a thinset mortar, also called dryset mortar, drybond mortar or simply “thinset.” Thinset mortar forms strong adhesive bonds in thin layers, making it the best choice for tile. Mixing thinset mortar is comparable to mixing standard mortar.

• Determine the amount of water and mix you’ll need for your job, based on the manufacturer’s recommendations. The standard mortar mixing ratio for thinset is one part mix to four parts water.
• Pour the water in the mixing container.
• Add the mix to the container.
• Blend for about five minutes.
• Slake the thinset mixture for 10 minutes.
• Blend for another five minutes, and check the consistency. If the mortar mix for tile has the peanut buttery appearance and adequate thickness, it’s ready for application.

Mortar is a workable, paste-like binding material used when building with brick, block, stone or other masonry materials. It is usually a blend of cement with fine sand as an aggregate, while concrete combines cement and coarse gravel as the aggregate. Lime can be added to make the mortar more workable and waterproof.

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