Mortar Joints & Tooling
Joint profiles for weather resistance including concave, raked, flush, and struck joints. Jointing tools, striking techniques, and proper tooling timing.
- Identify the most common joint profile for weather resistance
- Compare concave, raked, flush, and struck joint profiles
- Describe the proper tool used to smooth mortar joints
- Explain the correct timing for tooling joints
Lesson 1
Joint Profiles - Concave, Raked, Flush & Struck
Why Joint Profile Matters
The shape of a finished mortar joint directly affects how well the wall resists water penetration. Some profiles compress the mortar surface and shed water effectively, while others leave the joint vulnerable to moisture intrusion. Choosing the right joint profile is a critical decision for building durability.
Concave Joint
The concave joint is the most common joint profile for weather resistance. It is formed by pressing a rounded jointing tool into the mortar, creating a slightly indented, curved surface. This action compresses the mortar against the brick edges, sealing the interface where water would otherwise penetrate.
Best Weather Resistance
Concave joint - rounded inward, compresses mortar
V-joint - angled inward, sheds water to center
Both compress mortar against brick edges
Poor Weather Resistance
Raked joint - recessed, collects water on ledge
Struck joint - angled outward at bottom, directs water in
Both create ledges or channels that trap moisture
Raked Joint
A raked joint has mortar recessed back from the wall face, creating a shadow line for a dramatic visual effect. However, the ledge at the bottom of each joint collects water and is one of the poorest performers for weather resistance. Raked joints should only be used in protected or interior locations.
Flush Joint
A flush joint is cut even with the wall face using the edge of a trowel. It provides moderate weather resistance but does not compress the mortar the way a concave joint does. Flush joints are acceptable for general use but not ideal for severe exposure.
Struck Joint
A struck joint is angled so the bottom edge of the joint is recessed while the top is flush. This directs water inward at horizontal joints, making it one of the worst choices for weather resistance.
Exam Tip
The exam will ask which joint profile provides the best weather resistance. The answer is always the concave joint. It compresses mortar and sheds water effectively.
| Joint Type | Weather Resistance | Appearance | Best Use |
|---|---|---|---|
| Concave | Excellent | Rounded inward | All exterior walls |
| V-Joint | Very Good | Angled inward | Exterior decorative |
| Flush | Moderate | Flat with wall | General purpose |
| Weathered | Good | Angled outward at top | Horizontal joints |
| Raked | Poor | Recessed | Interior or protected only |
| Struck | Poor | Angled inward at bottom | Interior only |
The concave joint is the most common joint profile for weather resistance because it compresses the mortar surface and seals the mortar-brick interface. Raked and struck joints have poor weather resistance due to ledges that trap moisture.