The performance and longevity of any masonry structure are profoundly influenced by the mortar joints that bind its units together. While the brick or stone often receives the most attention, the selection and execution of the joint profile, or tooling, dictate the wall’s capacity to manage water, stress, and movement. Understanding the vast spectrum of brick mortar joint types is essential for architects, builders, and homeowners seeking to balance aesthetic vision with structural integrity.
The Functional Role of Mortar Joints
Beyond merely filling the gap between units, mortar joints act as the primary defense against the elements. They form a continuous barrier that prevents water infiltration, which is the leading cause of masonry deterioration. A properly designed joint accommodates the natural settling and shifting of a structure, preventing cracks from transferring through the rigid brick units. Furthermore, the compressive strength of the mortar itself contributes to the overall load distribution of the wall, ensuring the load is evenly transferred through the masonry wythes.
Common Profile Joints for Aesthetics and Water Management The visual character of a wall is largely defined by its profile joints, which are created by shaping the excess mortar after striking. Each profile directs water in a specific manner, making the choice critical for weather exposure. Raked Joints Created by cutting back the mortar flush with the brick face using a tool called a jointer, raked joints produce a distinct shadow line. This recess provides a cavity that shields the main mortar bond from direct water penetration, allowing moisture to drain away from the wall surface. Historically popular in traditional English and colonial architecture, this joint remains a favorite for its timeless, weathered appearance. Weather Joints (Struck Joints) One of the most practical brick mortar joint types is the weather or struck joint, where the mortar is tooled to create a sloping surface that directs water away from the wall. The slope is typically angled downward to prevent water from pooling on the horizontal surface. This method is highly effective in regions with high rainfall, as it encourages runoff before the mortar can absorb saturation. Specialized Joints for Structural Integrity
The visual character of a wall is largely defined by its profile joints, which are created by shaping the excess mortar after striking. Each profile directs water in a specific manner, making the choice critical for weather exposure.
Raked Joints
Created by cutting back the mortar flush with the brick face using a tool called a jointer, raked joints produce a distinct shadow line. This recess provides a cavity that shields the main mortar bond from direct water penetration, allowing moisture to drain away from the wall surface. Historically popular in traditional English and colonial architecture, this joint remains a favorite for its timeless, weathered appearance.
Weather Joints (Struck Joints)
One of the most practical brick mortar joint types is the weather or struck joint, where the mortar is tooled to create a sloping surface that directs water away from the wall. The slope is typically angled downward to prevent water from pooling on the horizontal surface. This method is highly effective in regions with high rainfall, as it encourages runoff before the mortar can absorb saturation.
Certain applications demand joints that prioritize function over form, focusing on movement control and structural cohesion.
Concave Joints
Formed with a curved steel tool, concave joints create a tight, hemispherical seal against the brick edge. This shape is exceptionally efficient at shedding water and is considered one of the most durable profiles for exterior work. The tight radius of the curve minimizes the surface area exposed to the elements, reducing the risk of mortar erosion over time.
Vee and Grapefruit Joints
Vee joints feature a tight, angular center that provides a strong mechanical bond, while grapefruit joints offer a slightly rounded, wide center. Both types are designed to handle significant movement without cracking. They are often specified in areas prone to settling or seismic activity, as the shape allows the mortar to flex slightly without failing.
The Challenge of Modern Materials
The introduction of modern, highly durable bricks and dense engineering stones has shifted the performance hierarchy of mortar joints. Because these units are less porous and dimensionally stable, they do not "give" easily under stress. Consequently, the mortar joint—being the softer element—must be designed as the primary movement joint. This often necessitates the use of specialized mortar mixes, such as those with polymer modifiers or enhanced plasticity, to ensure the joint can accommodate movement without shrinking or cracking.
Matching Joints to the Environment
Selecting the appropriate brick mortar joint types requires an analysis of climate, sun exposure, and building height. In freeze-thaw cycles, deep, tight joints like concave or extruded styles prevent water from collecting and expanding within the joint. Conversely, in hot, dry climates, wider raked or grape joints can accommodate the thermal expansion of the masonry units. Always consider the direction of prevailing winds and the amount of direct sunlight, as these factors influence the drying rate and thermal cycling of the mortar.
