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A crack in a render finish gets blamed on the render almost every time — but in the large majority of cases, the coating isn’t the problem. Unitex is direct about this in its own technical documentation: Unitex renders and finishes are not designed to bridge ongoing substrate movement, and where a building hasn’t been given anywhere for that movement to go, no coating on the market will stop it from eventually showing through as a crack. This piece covers what’s actually going on, where expansion and control joints are supposed to sit, and why getting this step right at the framing stage matters more than anything that happens once the render goes on.
This is a different cause to the substrate-porosity cracking covered in our guide on primers and sealers before rendering — that piece deals with render failing to cure properly on a porous substrate. This one deals with cracking caused by the building itself moving after the render has already cured.
Cracking Is (Usually) a Building-Practice Issue, Not a Product Fault
Where a builder or head contractor hasn’t provided adequate expansion or control joints, Unitex is explicit that the resulting cracking is not indicative of faulty material — it’s a sign of sub-standard building practice. The same applies where the substrate or frame itself wasn’t built to the relevant Australian Standards in the first place: cracking that follows is again not an indication of a faulty product.
This isn’t Unitex avoiding responsibility for a genuine product issue — it’s a straightforward physical reality. A render or texture coating is a thin, rigid-when-cured surface finish. A building frame and substrate underneath it will always move a little, through thermal expansion and contraction if nothing else. If that movement isn’t given a deliberate place to happen — a joint, designed and installed for the purpose — it will happen somewhere else instead, and a hairline crack through the coating is usually the first visible sign.
Specifying and installing expansion and control joints sits with the builder or head contractor, not the applicator. It’s a design decision made before render or texture ever gets near the wall, which is exactly why it needs to be right from the start rather than treated as something to fix after the fact.
Where Joints Need to Go
The standard rule for render, texture, and EIFS/Base Board coating systems is joints every 6 to 8 metres minimum on every elevation, and between floor levels. On top of that spacing rule, extra joints are needed at any point where the wall changes character in a way that changes how it moves — at junctions between dissimilar substrates (brick meeting Base Board is a common one), at bulkheads, and around window and door openings.
The logic is the same in every case: anywhere the substrate isn’t structurally continuous, or isn’t made of one uniform material, is a point where differential movement is more likely — and therefore a point that needs its own joint rather than relying on the nearest elevation joint several metres away.
How Joints Are Sized — And a Detail Worth Getting Right
For render, texture and EIFS coating systems specifically, the typical joint is 8–10mm wide, sealed to a depth of roughly 5–7mm with a flexible polycarbonate mastic. One detail that’s easy to get backwards on site: the render or coating thickness needs to be thicker than the mastic depth requires, not the other way around. Sizing the coating to the mastic, rather than the mastic to the coating, is a common enough mistake that it’s worth flagging explicitly before the job starts, not discovered at the joint once the coating’s already gone on.
It’s worth noting these figures apply specifically to render, texture and EIFS/Base Board coating systems. Uni-Shape architectural mouldings, being mechanically fixed rather than trowelled or sprayed on, use a different set of expansion joint figures entirely — that’s a separate topic in its own right, and the two shouldn’t be assumed to be interchangeable.
What Happens When a Builder Disputes the Need for Joints
Because expansion joints are a design responsibility, not an application-technique choice, disagreements do come up on site — a builder or head contractor sometimes pushes back on the need for a joint a rendering contractor knows should be there. Unitex’s own guidance for applicators in this situation is unusually direct: where a builder disputes the need for a joint, the recommendation is for the applicator to get written instruction from the builder releasing them from responsibility for any resulting cracking, rather than proceeding on a verbal disagreement with no record of it.
That’s a genuinely useful, practical piece of advice for any rendering contractor, and worth having on hand before a dispute happens rather than working it out mid-argument on site.
Frequently Asked Questions
Do I really need expansion joints?
Yes. They’re standard building practice, not an optional extra or a sign something’s gone wrong with the design. Skipping them is one of the most common — and most avoidable — causes of render and texture cracking.
Who’s responsible for installing expansion joints — the applicator or the builder?
The builder or head contractor. Specifying and installing expansion and control joints is a design and construction decision made before rendering begins, not something the rendering applicator controls or is responsible for.
If my render has cracked, does that mean the product has failed?
Not necessarily, and often not at all. If the crack lines up with a substrate junction, a missing joint location, or a point where the frame or substrate wasn’t built to the relevant Australian Standard, the coating is very unlikely to be the cause.
Can a render crack caused by a missing expansion joint be fixed just by patching over it?
Patching the surface without addressing the underlying movement generally doesn’t hold — if the substrate is still moving at that point and there’s still nowhere for that movement to go, a repair in the same spot is likely to crack again over time.
Get It Specified Right From the Start
Whether you’re a builder finalising a set of plans or a rendering contractor about to quote a job, it’s worth having Unitex’s technical sales team look over the joint layout before render or texture goes on, not after a crack shows up. Call 1800 RENDER or email sales@unitex.com.au with your plans, and they can talk through joint placement, sizing, and product selection for your specific project.
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