Mortar Joint Profiles - A Brief Guide
The external finish of a mortar joint will vary. Each type affects the overall look as well as impacting durability and water-resistance. Mortar joints provide both structural integrity and weatherproofing for masonry construction. You may be familiar with a few commonly used joints, others however are scarce. Like everything else, mortar joints have evolved in response to developments in technology and building requirements. This has affected the quality and strength of materials used, tools and application techniques, and purpose. While many joint types are now outdated, it is still preferable for a building’s character that the original joint type is faithfully replicated during the restoration process. There are also regional adaptations and name variations, making it near impossible to document each type. We have listed a few of the main joints below for visual reference.
Concave Mortar Joint
The mortar joint is compressed and curved in at the centre, formed by a curved steel jointing tool. It hides small imperfections in the brickwork and is commonly used for exterior construction because of its high resistance to water penetration, a result of the tight seal that can be achieved in this joint.
Concave mortar joint. Image: Raysonho - Grid Engine
Flush Mortar Joint
The mortar is flush with the edge of the brickwork. These joints are mainly used when the surface is to be plastered or concealed with paint, and require more time to ensure they are watertight.
A brushed flush joint is filled as a flush joint but brushed back to create a textured appearance to add character on non-rendered walls.
Flush mortar joint. Image: Titus Tscharntke
Struck Mortar Joint
Used horizontally, the mortar tapers in towards the base (struck up), opposite to the weathered joint. This joint type is mainly used for interior walls as water can sit on the top of the brick and seep in if exposed. It was originally (circa. 15th Century) developed as a way of disguising irregularity of bricks by defining one straight edge and allowing the mortar to merge with the other.
Weathered Mortar Joint
Used horizontally, the mortar tapers in towards the top (struck down) creating a shadow line effect. This joint encourages water runoff, however there are risks of shrinkage and water seepage if not properly executed. The joint dates back to the 19th Century and has a more polished version, weather-struck and cut, which involves joints being trimmed and refined.
Grapevine and Ruled Mortar Joint
This joint features a small indentation running through the middle of the joint, sometimes executed in an irregular or “grapevine” design, and is created using a grapevine jointer. The joint is popular for antique style brickwork and to replicate colonial style masonry.
Grapevine is said to have replaced the originally termed ruled joint (used in the early 17th Century), which was used to achieve a more refined and narrower looking joint.
Grapevine is also mentioned in reference to Bastard Pointing, which was originally a less sophisticated copy of tuck pointing, where the groove was later infilled with white, red or black putty.
Grapevine or bastard Pointing. Image: timsackton
Raked Mortar Joint
The mortar joint is recessed with a consistent vertical finish which emphasises the joint. It is now used mainly for interior construction as the exposed ledge can allow water and ice to settle on top of the bricks. Raked joints were often used in early 20th homes.
Raked mortar joint. Image: Tomwsulcer
V Mortar Joint
The mortar is recessed in a V shape by using a formed tool in the mortar to create a more decorative but crisp finish. This joint encourages water runoff and helps prevent water build up in the brick.
Extruded Mortar Joint
The mortar sits out beyond the brickwork creating a less refined and textured look. These joints are created by excess mortar being pushed out as the bricks are laid. There is risk of deterioration over time with this finish and it is recommended for interior use.
Extruded mortar joints
Beaded or Convex Mortar Joint
This joint features an extruded curved joint that results in a formal finish and is often used in restoration of historical stonework. This is not a highly weather resistant finish due to exposed mortar. An extruded square profile is referred to as a ribbon or box joint.
Beaded Mortar Joint.
Tuckpointing
Tuckpointing incorporates two tones of mortar to produce a sharper finish. Mortar matching the brick is used to first to fill, followed by the tuck, usually in white (occasionally black or red). The tuck creates definition and the appearance of narrower joints. Tuckpoint joints were originally (17th Century) used to disguise poorly formed bricks and uneven courses in masonry work. In Australia it was common towards the end of the 19th Century and particularly prevalent in Edwardian brick facades.
Tuckpointing. Image: Jonathanriley
Further information on mortar joints and masonry repair
Government of South Australia - Heritage Conservation - Technical Guides
Government of Western Australia - Conservation - Technical Advice Sheets
National Trust - Publications - Preservation of Masonry Walls
Building Conservation - Articles - Joint Finishes on Historic Brickwork