Articulation Joints In Brick Veneer Houses

A long brick wall with no joints in it will crack. Not sometimes, reliably.

Articulation joints are vertical joints built into the brickwork, filled with a compressible material and sealed, that let the wall move without cracking.

What the movement is

Several things acting at once.

Clay brick expansion. New clay bricks absorb moisture after firing and grow slightly over the first several years. Permanent, irreversible, and it never stops entirely.

Thermal movement. The sunny wall expands and the shaded wall does not. Over a long wall that difference is real.

Footing movement. On a reactive clay site the footing moves seasonally, and the brickwork above it has to accommodate the shape change. This is the dominant cause on most [Sydney clay sites](/blog/reactive-clay-sites-footing-design-nsw).

Differential movement between materials. The brick veneer skin moves differently from the timber or steel frame behind it and from the concrete slab below it.

Where the joints go

Not arbitrarily. The rules follow where stress concentrates.

At re-entrant corners, where a wall steps in or out. This is the most important location and the one most often missed.

Beside openings, particularly large ones, and where a return wall is short.

At changes in wall height, such as where a single storey section meets a two storey one.

At changes in the structure behind, including where the veneer passes from a slab onto a suspended section.

At intervals along long straight runs, and the maximum spacing depends on the site classification. A more reactive site needs joints closer together.

Where the wall changes direction or passes a control joint in the slab, which follows the same logic as [expansion and control joints in concrete](/blog/expansion-and-control-joints-in-concrete).

What a joint actually is

A full height vertical gap through the brickwork, from the damp proof course to the top of the wall.

The gap is filled with a compressible filler and finished with a flexible sealant, coloured to suit the brick. Done properly it is barely visible. Done badly it is a stripe down the wall.

The joint has to be continuous, and this is the part most often defeated. A joint that stops at a window head or is bridged by a course of bricks does nothing, because the wall is still continuous at that point.

Ties across the joint have to allow movement in plane while still restraining the veneer, which means slip ties rather than standard ties at those locations.

The failures we see

No joints at all, in older houses and in newer ones where the bricklayer was not instructed.

Joints in the wrong place, spaced evenly along a wall and absent from the corners where they were actually needed.

Joints bridged by render, by a course of bricks, by a sill, or by a rigidly fixed downpipe bracket.

Sealant perished. Sealant has a service life. An unmaintained joint eventually becomes a water entry path, which is a different problem to the one it was solving.

Render over the top, which is the most common way a properly built joint gets defeated. A rendered finish over an articulation joint needs a matching joint in the render, or the render cracks along the line.

Reading a crack in brickwork

Where a wall has cracked, the location tells you what was missing.

A vertical or stepped crack at a re-entrant corner, or running up from a window, is almost always the wall articulating itself where no joint was provided. The mechanism is covered in [cracking in brickwork](/blog/cracking-in-brickwork-what-it-means).

Retrofitting a joint into a cracked wall is possible: cut a joint on the crack line, clean it out, install the filler and seal it. That stops the crack widening and makes it maintainable, which is usually a better outcome than repointing a crack that will simply reopen.

The design responsibility

Joint locations belong on the drawings, not in the bricklayer's judgment.

They depend on the site classification, which comes from the [soil investigation](/blog/site-classification-soil-investigation-basics), and on the geometry of the building. Both are known at design stage and neither is obvious on site.

ACSES provides structural engineering for residential projects and masonry assessment across Sydney. Get in touch.