ClayBrick: Mortar & Your Walls

There are quite a few essentials that work together to make your walls solid and strong. Mortar is one such staple that not only holds your bricks together – it can be a characterful design element with the use of contrasting or complementary colours!

We take a closer look at mortar and how you can use this to transform your walls.

Mortar & Your Walls

Did you know that mortar makes up approximately 15% of your brick wall?

The primary function of mortar is to help bond bricks together, allowing the brickwork to act as a structural element to carry both vertical and lateral loads. The second function of mortar is to accommodate for any dimensional variations of individual units as the masonry is laid. Good mortar will provide structural, weatherproofing, and aesthetic benefits to your building.

What is the difference between mortar and cement?

Mortar is different from cement and grout. Cement can be used on its own to build walls while mortar is used to hold parts of a wall together. While both concrete and mortar construction are durable, their strengths lie in different areas. Concrete is objectively stronger than mortar and can be applied in large quantities. Mortar isn’t meant to be used in thick applications and is better to work with than concrete.

While mortar has a lower strength than concrete, it has the ability to retain water, and it has a high air content. This means that when temperatures freeze and the water in the mortar expands into ice, the ice moves into the air bubbles, preventing the mortar from cracking. Mortar, therefore, provides structural integrity to a wall, floor, or other structure but is flexible enough to allow shifting without cracking.

Typical components of mortar include sand, cement, lime, and water. The proportioning of each mortar constituent will depend on your desired balance of workability and performance.

The cost and quality of masonry work is significantly affected by the mortar used. Mortars may account for as little as 7% of the volume of the walls, but the role it plays and the influence it has on performance are far greater than the proportion indicates. Mortar provides a bed for laying; bond units together to give compressive and flexural strength and seals joints against rain penetration.

What are the mixing quantities?

Mortar must not be used after it has started to set, which usually occurs about two hours after it has been mixed. One man – particularly if he is a weekend builder – can probably lay a little more than 60 bricks an hour. If you are working on your own or with one assistant, it is better to mix a number of small batches as they are required than to mix a one-bag batch. Do not use too thick a layer of mortar between bricks or blocks; this is wasteful and may lead to cracking.

Mortar class

Class I: Highly stressed masonry incorporating high-strength structural units such as might be used in multi-storey load-bearing buildings; reinforced masonry.
Class II: Normal loadbearing applications, as well as parapets, balustrades, retaining structures, and freestanding and garden walls, and other walls exposed to possible severe dampness. In practice, Class II mortars are used for most applications.
The amount of water added to a mix must be enough to make the mix workable and plastic

Masonry cement must comply with SANS 50413-1: Strength class 22,5X. The addition of lime to masonry cements is not permitted.

MORTAR:
For laying bricks and blocks in normal applications (SABS Class II)
To lay 1000 bricks = 3 bags cement + 0.6 cu. m. sand
1 Bag of cement to 3 wheelbarrows of building sand

PLASTER:
For exterior and interior work
To lay 100sq.m. (15mm thick) = 10 bags cement + 2 cu. m. sand
1 Bag of cement to 3 wheelbarrows of plaster sand

The CBA represents the clay brick and paver manufacturers of Southern Africa. They inspire sustainable, contemporary brick architecture and building design in all areas of the built environment: commercial, residential and landscape.