Frequently, a major consideration in selecting masonry is an appreciation for its appearance. Many people find masonry beautiful. That fact, coupled with a continuing trend toward more dramatic architectural use of color and texture in building design, has resulted in greater emphasis on achieving the desired appearance in finished masonry mortar joints. This article introduces the factors that determine the color consistency of mortar joints and how certain construction practices and techniques influence its appearance.

Achieving acceptable appearance of mortar joints on a project requires:

1. initial agreement between the owner or his representative and the contractor or mason on what constitutes desired appearance


2. an understanding by both of the inherent limitations of the system


3. careful control of influencing variables by the contractor and mason

Mockups and Sample Panels

The masonry sample panel or mockup is an important means of establishing agreement between purchaser and provider on what is expected and what is achievable [see “Masonry Walls and the Importance of Mockups”]. Establishing appearance criteria for the project is one of the basic reasons for constructing, approving, and retaining sample panels or mockups.

What Affects Joint Color?

There are several things that affect the color of mortar joints from designer and builder viewpoints: materials, proportioning of the mortar, moisture condition of the masonry units, tooling, and cleaning procedures. The contractor obviously has quite a bit of influence on the appearance of joints in the finished wall.

Controlling Appearance

To achieve the most uniform color, there are basic principles to adhere to, and they all come back to one issue: Aim for as little variation as possible. The goal is to try to do everything the same way each time. This helps minimize differences in appearance.

Masonry units should be stored on pallets above the ground, and should be protected with tarps. This keeps them at more uniform moisture conditions, which minimizes differences in behavior when they come into contact with mortar.

Use the same mortar materials for the entire project. Changing brands or suppliers should be avoided. If it is possible, consider storing enough materials at the site before the job begins.

Keep sand and cement proportions consistent from batch to batch. Water contents will vary according to the needs of the mason and the changing weather, but that variation is primarily to accommodate placement of the masonry units.

In addition to exercising careful batching procedures, mix materials consistently to get the most uniform results. Charge the mixer with materials in the same order each time, then mix the mortar for the same amount of time. Colored mortars should be mixed for the full amount of time to assure thorough blending of the pigment.

The effect of tooling on the appearance of a mortar joint is dependent on the type of jointer used and the stiffness of the mortar at the time it is tooled. When tooled at the proper consistency, the surface of the mortar joint is compacted, and a uniform appearance consistent with the body of the mortar is achieved. Since pigments, due to their high fineness, are easily concentrated on the surface of a mortar joint by tooling, the appearance of colored mortar joints is especially sensitive to the tooling technique used in finishing the mortar joint.

Good workmanship minimizes mortar droppings and smears on the face of the masonry. That results in less need for cleaning. In addition to saving time and labor, the wall looks better. But even with the best construction practices, some cleaning may be necessary. The least aggressive method should be chosen to protect both the units and the joints from damage. Like before, the goal is to do everything the same way each time, so keeping cleaning procedures the same on all wall areas results in the most uniform appearance.

Masonry is a handcrafted material and it is affected by constituent materials, weather conditions, and construction practices. It is easy to see how contractors have so much influence on the appearance of the masonry. Knowing the right techniques is a great start to achieving uniform color and texture on walls, and especially, on mortar joints.

For more information see PCA's publication: Mortar Color (IS247)

 
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