Mortar is a common bonding agent for building materials such as bricks, stones, and concrete blocks. It’s made of water, sand, and cement in varying ratios. This mixture has many types, and each of them differs in strength, flexibility, and adhesion.
Before buying a mortar for your project, you have to understand the properties of the different types first. This will help you determine which one will work best for the job.
Here’s some information on the 3 common types:
This general-purpose mortar can be used for interior, exterior, and above-grade load-bearing installations. It has medium to the high compressive strength of 750 pounds per square inch (psi). It’s made up of 1 part Portland cement and lime and 6 parts sand. This gives the structure more resilience and flexibility.
Type N is the most common mortar used by homeowners for general applications. It’s ideal for walls that are exposed to severe weather, low temperature, or extreme heat. It’s also good for freestanding and non-load-bearing structures, such as planters and dividers. It prevents semi-soft stones from cracking as well because it’s flexible.
This is primarily used for interior, above-grade, and non-load-bearing walls. It’s made up of 1 part cement, 2 parts lime, and 9 parts sand. It can be an alternative to Type N for internal purposes, but its exterior applications are limited because of its low strength (350 psi). This isn’t recommended for areas that are subject to high wind and intense temperatures.
But, mortars with low psi aren’t inferior to those with high strength. They have more superior adhesive and sealing powers. Because of this, Type O is great for repointing and repairing existing structures.
It’s commonly used for load-bearing structures and below-grade applications, like foundations, retaining walls, and driveways. It’s also great for anything that’s exposed to frost heave. Type M is composed of 1 part lime, 3 parts Portland cement, and 12 parts sand, and is the strongest mortar with a compressive strength of 2,500 psi.
It’s the number one choice for natural stones because of its durability. But, despite its immense compressive strength, it has low bonding ability and sealing properties. So, it’s not ideal for most exposed applications or tuckpointing.
When working on a masonry project, you should always give plenty of consideration to the type of mortar concrete mix you’ll choose. It plays a big part in the overall strength and durability of the structure.