What is a mortar joint?
A mortar joint is the seam between two bricks, natural stones or tiles that is filled with mortar or jointing compound. Joints provide the bond between the bricks, distribute forces and make the wall watertight. The finish of the joint also contributes to the appearance of the brickwork.
Types of joints
Bed joint (horizontal)
The horizontal seam between two brick courses. Standard thickness: 10-12 mm.
Perpend joint (vertical)
The vertical seam between two bricks in the same course. Standard thickness: 10 mm.
Joint finishes
The way the joint is finished determines the appearance and weather resistance:
| Type | Description | Water resistance |
|---|---|---|
| Flush joint | Finished flat with the brickwork | Good |
| Recessed joint | Set back slightly (2-3 mm) | Moderate (water can pool) |
| Concave joint (bucket handle) | Rounded out with a jointing iron | Good (water runs off) |
| Weathered joint | Top recessed, bottom flush | Good, decorative |
| Struck joint | Mortar protrudes slightly | Less good (breaks off easily) |
Joints and mortar
The joint is filled with mortar — a mixture of cement, sand and water. The mortar strength must match the brick type:
- Soft bricks (handmade) — soft mortar
- Hard bricks (machine-made) — hard mortar
Too hard a mortar with soft bricks causes the bricks to crack rather than the joint.
Repointing (replacing joints)
In older walls, joints deteriorate. Repointing:
- Rake out old joint — With a joint raker or angle grinder, minimum 15-20 mm deep
- Blow out/rinse — Remove dust and loose debris
- Dampen — Dry brickwork will suck the moisture out of the jointing mortar
- Apply jointing mortar — With a jointing iron or pointing gun
- Finish — Apply the desired joint profile
Related terms
- Bond pattern
- Mortar
- Half brick wall
- Single wythe wall