Brick walls look solid and still, but they are not. They grow and shrink slightly with heat, cold and moisture. Over a short wall, this movement is too small to notice. Over a long boundary wall or the full length of a building, it adds up. If the wall has nowhere to move, it relieves the stress the only way it can: by cracking.

Expansion joints, also called movement joints, give the masonry a planned place to move. This guide explains why brickwork moves, where joints are usually needed, and what goes into a properly made joint.

Why brickwork moves

Moisture expansion of clay bricks

This surprises many people. Fired clay bricks start absorbing moisture from the air as soon as they leave the kiln, and they slowly expand. Most of this happens in the first few weeks and months, and some continues for years. The expansion does not reverse. Freshly fired bricks laid straight into a wall are more likely to cause movement problems than bricks that have been allowed to settle for some time.

Thermal movement

Brick walls heat up in the sun and cool down at night. In Punjab and much of North India, the gap between a summer afternoon and a winter night is large. Walls facing south and west, dark coloured walls and parapets exposed on both sides see the biggest swings.

Different materials moving differently

Concrete and cement-based materials tend to shrink as they dry, while clay brickwork tends to expand. Where a brick wall meets an RCC column, beam or slab, the two materials pull in opposite directions. This is one of the most common places to see cracks in modern buildings.

Ground and structural movement

Settlement of foundations, deflection of beams and slabs, and changes in loading all cause some movement. Joints are not a cure for structural problems, but they help the wall cope with normal movement without cracking.

Where movement joints are usually needed

The exact spacing and location should be designed by your structural engineer, based on the brick type, wall height, exposure and structure. But these are the places where joints are commonly considered:

Long continuous walls

Long straight runs of brickwork, especially boundary walls and long external walls, need vertical joints at intervals. A spacing of roughly 10 to 12 metres is often used as a starting point for clay brickwork, with closer spacing for parapets and exposed walls. Your engineer may set a different figure.

Near corners and returns

A long wall expanding towards a corner pushes against the return wall and can crack it. Joints are often placed within a short distance of corners rather than right at them.

Junctions with RCC frames

Where brick infill meets columns or sits under beams, the contact needs attention. A gap with compressible filler under a beam, or a properly detailed joint at the column face, allows the frame and the brickwork to move independently.

Changes in wall height or thickness

Where a tall wall meets a short wall, or where thickness changes, stresses concentrate. A joint at that change reduces cracking.

Parapets and free-standing walls

Parapets and boundary walls are exposed on both sides and at the top. They heat and cool faster than the main walls below and are among the most crack-prone parts of any building. They usually need closer joint spacing.

Around large openings

Big window and door openings weaken a wall locally. Joints are sometimes aligned with the edges of openings so that cracks do not start from the corners.

Where a new wall meets an old one

Older brickwork has already finished most of its moisture movement. New brickwork has not. Tying the two together rigidly invites cracks at the junction.

What a proper movement joint looks like

A movement joint is not just a gap left in the wall. A good joint has a few parts that work together.

• A clear gap: Usually around 10 to 15 mm wide, running the full height and thickness of the wall. It must be kept free of mortar droppings and debris, because a joint filled with hard mortar does not work.
• Compressible filler: A soft, flexible filler board or foam that fills the depth of the joint and squeezes as the wall expands.
• Backer rod: A foam rod near the surface that controls the depth of the sealant and stops it sticking to the back of the joint.
• Flexible sealant: A weather-resistant sealant, such as polyurethane or polysulphide, on the exposed face to keep water out while allowing movement.
• Ties where needed: In some walls, flexible or slip ties across the joint keep the two sides aligned while still allowing lengthwise movement.

On plastered walls, the joint must continue through the plaster too. Plastering over a movement joint simply moves the crack into the plaster.

Common mistakes

• Leaving the gap in the brickwork but filling it with mortar or plaster later.
• Not continuing the joint through copings, plaster or finishes.
• Using rigid fillers that cannot compress.
• Building long boundary walls with no joints at all.
• Placing fresh, hot bricks straight from the kiln into long walls.
• Using poor-quality sealant that cracks or peels within a year or two.

Maintaining joints

Sealants wear out with sun and weather. Check movement joints once a year, ideally before the monsoon. Look for sealant that has cracked, hardened, pulled away from the edges or gone missing. Replace it before water gets in. A failed sealant lets rain into the wall and can cause damp, efflorescence and further damage.

Related reading: you may also find our guides on choosing the best bricks for a boundary wall and brick coping design useful.

Quick summary

Brick walls expand with moisture and move with temperature, while concrete tends to shrink. Movement joints give the wall a planned place to move instead of cracking. They are usually needed in long walls, near corners, at RCC junctions, at changes in height, in parapets and boundary walls, and where new meets old. A good joint has a clear gap, compressible filler, backer rod and flexible sealant, and it carries right through the finishes.

Choose Reliable Bricks from Mahaluxmi Bricks

Good detailing works best with good materials. Mahaluxmi Bricks is a trusted bricks manufacturer in Punjab, based in Dera Bassi, supplying well-burnt, machine-made red bricks for boundary walls, houses and commercial buildings. Our bricks are made for consistent size and strength, which helps your masons build straight, even walls with clean joints. For quality red bricks in Punjab and timely bulk supply, connect with our team.

Visit Mahaluxmi Bricks – Red Bricks Manufacturer in Dera Bassi, Punjab for rates and enquiries.