Raked joints are a traditional masonry technique where mortar is deliberately shaped with a sloping surface, creating a distinct visual groove between the bricks or stones. This method has been employed for centuries, not merely for aesthetic effect, but as a practical solution for water runoff and structural integrity. The angle of the rake prevents water from pooling on the surface, directing it away from the mortar bed to significantly extend the lifespan of the wall. While often associated with historic architecture, the practice remains highly relevant in contemporary construction for its blend of durability and classic charm.
Understanding the Purpose and Function
The primary function of raked joints is hydraulic. By creating a recessed channel, the joint ensures that rainwater does not sit on the mortar line. Standing water can freeze in cold climates, causing spalling, or seep into the wall’s internal structure, leading to dampness and salt damage. The slope acts as a natural drainage system, allowing gravity to pull moisture away from the brickwork. Furthermore, the compressed mortar at the edges of the raked groove provides a harder finish, resisting erosion compared to a flat, flush joint that wears down over time.
Visual Appeal and Architectural Style
Aesthetically, raked joints add texture and definition to a wall, making each brick a distinct element rather than a uniform block. The shadow line created by the depth of the rake adds depth and dimension, enhancing the visual weight of the structure. This technique is particularly prevalent in period properties, such as Victorian terraces and Georgian townhouses, where it complements the masonry’s historical authenticity. Modern architects also utilize raked joints to evoke a sense of heritage or to provide a stark contrast against smooth, rendered backgrounds, proving its versatility across design eras.
Common Rake Profiles and Variations
Not all raked joints are created equal; the profile refers to the specific shape cut into the mortar. The most common is the straight rake, where the mortar is cut at a consistent angle, usually between 45 and 60 degrees, creating a clean, linear look. A rounded rake, also known as a bucket handle profile, uses a semi-circular tool to create a softer, more curved indentation. Another variation is the struck joint, where the mortar is trimmed flush to the face of the brick on one side, often at the bottom of the wall to direct water away from the brick above.
Tooling and Application Technique
The creation of a raked joint requires specific tooling and timing. After the mortar is placed between the bricks, it must be allowed to set slightly until it is firm but still pliable—typically within one to two hours. A raking tool, which features a hooked or angled metal shaft, is then used to scrape out a consistent depth of mortar. It is crucial to maintain a steady hand and uniform pressure to ensure the groove is even along the entire length. The process must be done carefully to avoid disturbing the brick alignment or weakening the mortar bond.
Maintenance and Longevity Considerations
While raked joints are durable, they do require specific maintenance to preserve their integrity. The recessed areas can sometimes trap organic debris like moss or algae, which should be gently brushed away to prevent staining. Re-pointing is necessary over decades as the mortar naturally erodes; however, the process is more complex than with flush joints. It is vital to match the original rake profile and mortar composition to maintain the structural effectiveness and historical accuracy of the wall. Using a soft brush and low-pressure washing is recommended to clean the grooves without causing damage.
