What is Concrete Masonry Unit, Advantages, Sizes, Configuration, Systems

CMU – Concrete Masonry Unit

Concrete Masonry Unit Advantages Sizes Configuration SystemsA lot of people are familiar with CMU and that is because they have been used for a very long time now. In fact, if you look around, you’ll realize that every low rise building is made using these materials, from industrial, to commercial, education and also residential buildings. Not only do they offer the buildings a great aesthetic appeal, but they’re also durable as well.

To make CMU, manufacturers need to use very stiff and dry concrete mixtures. The way it goes is that the low slump or no slump material will be placed into the appropriate molds, vibrated, compacted and eventually de-molded swiftly. When they finally make it to the curing chamber, the units will be stiff enough to hold their shape. Next, they’re palletized and prepared for shipping.

History and Overview

In the last century, concrete masonry units have transitioned from the traditional hand cast process to one that is 100% automated. This means that presently, CMU are produced to a much higher standard of quality and also much faster than ever before.


Determining which attribute of concrete masonry units is its best can be harder than you can imagine. However, given the fact they are non-combustible is really important. On top of that, they also offer a great finish, are long lasting, very durable and can be easily reinforced in order to meet demanding structural applications. Depending on the client’s needs, they may also contain recycled materials, but don’t require any types of treatments to preserve their properties and contain no VOCs or other possibly dangerous off-gassing materials. Lastly, they provide thermal mass which helps a lot in maintaining uniform temperatures.

If we are to look at it from a construction perspective, one thing that’s really amazing about CMUs is that it doesn’t require too much space to stage the construction. Even though it’s a bit harder to build, compared to other materials out there, it’s can be easily made and can also be produced in larger quantities since the materials needed to make it are available off the shelf.

Systems, Configurations, Components And Sizes

Since CMU is modular, the most common size is a nominal eight by eight by sixteen inches. In order to minimize cutting of units, window and door openings need to be positioned in a certain way. Walls containing a single vertical layer of units are known as single wythe, while if they contain 2 layers, they’re known as double wythe. Building these types of walls is very common and when they’re separated using a continuous vertical space, the assembly will be known as a cavity wall. The units are then going to be held together using mortar.

Concerning proper reinforcement, the units are going to be placed into vertical and horizontal cavities as required using grout. By doing so, the walls will be able lot resist the forces that act on them and also carry loads.

For exterior and interior faces, insulation can be added inside special unit cavities and between withes as well. One pro about keeping the insulation inside the wall is thanks to the durability of the masonry faces. But in order to complete the wall, attach finishes and promote proper drainage, extra accessories may be required.

If you’d like to look at something potentially better than CMU’s look at this video:

Article by Echevarria Mendez

I've been working with concrete all my life. It's a material to admire for its strength and beauty.