Mortar and Mortar Joints in Brick Walls

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Mortar joints bond bricks together, allowing the brickwork to act as a structural element to carry both vertical and lateral loads.

Properly filled and tooled joints improve the durability, weather-proofness, and sound performance of brickwork. Raked or recessed joints should be avoided in applications where durability is critical, such as in saline environments. (It is, however, recommended that a raked joint be used for bricks with a beveled edge.)

Colour

The color and style of mortar to be used are equally as important as choosing the bricks themselves. Mortar color and style can dramatically change the overall look of your home or building, so it is important to be aware of the different colors and styles available. Some colors and their basic compositions are outlined in table 1.

Table 1. Approximate mortar compositions based on color.

Colour

Sand

Oxide

Cement

Red

Yellow

Red

Natural

Brown

Yellow

Brown

Natural

White

White bush

-

White

Off white

White bush

-

Off white

Black

Yellow

Black

Natural

Natural

Yellow

-

Natural

Cream

Yellow

-

Off white

Yellow

Yellow

Yellow

Off white

 

Pigmented mortars must be strong enough to retain the pigment particles on the face of the joint. In weak mortars, the pigment particles may rapidly be eroded from the face of the joint by wind and rain.

Acid cleaning of brickwork may also degrade pigment color, leading to faded, patchy, and unattractive mortar joints. For durable pigmented mortar, always finish the joint by tooling even when a raked joint is required.

Batching Mortar

Unless the proportions of sand, lime, and cement that go into a mortar mix are measured carefully, it is impossible to be sure if the correct mix has been achieved.

To ensure that the correct proportion of materials has been used it is suggested that batching be carried out using buckets. Using a shovel to give the same effect is ineffective because the shovel can hold more sand than cement.

Mortar mixes are always specified as the proportion of cement to lime to sand, and always in that order. A common mortar made from Portland cement has one part cement to one part lime and 6 parts of sand (abbreviated to C1:L1:S6, or simply 1:1:6).

The Addition of Lime to Mortar

The addition of lime to mortar has the advantage of making the mortar workable in the wet state and may eliminate the need for plasticizing admixtures.

Mortar containing lime will be less pervious, more durable, and more ‘forgiving’ than a mortar without lime.

Other Mortar Additives

Commonly approved additives include:

  • Plasticizers or workability agents, including air-entraining agents
  • Cellulose type chemical water thickeners
  • Coloring agents
  • Set-retarding chemical agents
  • Bonding polymers

Other admixtures may not be used unless tests have demonstrated compliance with the requirements of local standards.

Types of Mortar Joints

Shown below are the different styles of mortar joints that can be used.

This article was updated on 7th February, 2020.

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