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Finding the Right Type of Mortar

By September 28, 2012September 6th, 2023No Comments

Stepping into a home improvement store, do you ever find yourself wondering which mortar is the right fit for your latest project?

Navigating the vast array of mortar options available can be a daunting task, especially for those new to home construction. Whether you’re planning to build a walkway or embark on a brick oven project, selecting the appropriate mortar type hinges on your project’s specific requirements. Having a solid grasp of these mortar varieties can significantly streamline your shopping experience, ultimately saving you both time and money.

For valuable insights on pinpointing the perfect mortar type for your project, refer to the informative article from FineHomeBuilding.com. This resource provides essential tips to help you make an informed choice and set your project on the path to success.

Mortar: What Type Do You Need?

Understanding the types of mortar will help you choose the one with the right properties for your project

by David Ericson

Mortars are often ordered based on compressive strength; but even more important properties are bond strength and flexibility. Bond strength and flexibility work together, holding masonry units in place yet flexing in response to lateral loads or expanding and contracting in response to temperature swings.

Premix or self-mix? Mixing cement and lime on-site provides flexibility to a skilled mason but requires careful measuring. Pre-mixed masonry cement ensures consistency but rules out on-site fine-tuning of the recipe.

What is mortar made of?

To achieve the balance of properties for a particular application, you mix different proportions of portland cement, hydrated lime, sand and water. Portland cement yields greater compressive strength but lower water retention during the cure, thus risking shrinkage cracks. Lime yields lower compressive strength but greater bond strength and flexibility. Sand, the aggregate, adds volume and minimizes shrinkage as the cement dries. Water makes the mix workable and activates hydration, the chemical reaction that hardens the cement.

Type M: high compression strength

Type M has the highest proportion of portland cement, with 3 parts portland cement, 1 part lime and 12 parts sand. Type M has a high compressive strength (at least 2500 psi) and is recommended primarily for walls bearing heavy loads, but also, due to its durability, for masonry below grade or in contact with the earth: foundations, retaining walls, sidewalks and driveways.

Type S: compression and tensile strength

Type S is sometimes specified for masonry at or below grade, but offers another quality. S has high compressive strength (1800 psi) but adds high tensile bond strength. S contains 2 parts portland cement, 1 part hydrated lime and 9 parts sand, and yields maximum flexural strength to fight wind, soil pressure or earthquakes.

Type N: for exterior, above-grade walls

Type N is a medium compressive-strength (750 psi) mortar made of 1 part portland cement, 1 part lime and 6 parts sand. Type N is recommended for most exterior, above-grade walls exposed to severe weather, including chimneys.

Type O: for interior or non-load-bearing use

Type O has a low compressive strength (about 350 psi), containing 1 part portland cement, 2 parts lime and 9 parts sand. O is recommended for interior and limited exterior use in non-load-bearing walls.

This straightforward list can be your saving grace, alleviating any stress and uncertainty during your trip to the hardware store. Armed with newfound knowledge about mortar choices, you’ll amaze your friends and family with your informed decisions. While mortar might appear inconspicuous, choosing the correct type can be the difference between a resilient walkway and one that shatters under the weight of you and your bulky winter attire.

Before you make your final decision or if you’d like a second opinion, consider reaching out to Camosse Masonry¬†. We’re here to provide you with the right supplies, ensuring that you get the most value for your investment. Remember, when it comes to mortar, it’s essential to do your homework and select the optimal mortar for your specific project. After all, as the saying goes, “One does not simply walk into mortar.”