Render protects masonry and gives a building its finish. When it cracks, bubbles, sounds hollow or falls off, the question is whether the render itself has failed, or whether something behind it is causing the damage.
Three common situations
Fine cracks only: patch and repaint
Hairline cracks from shrinkage, with render still firmly bonded, can usually be filled and recoated with a flexible coating.
Drummy or bulging render: remove and re-render
Tap the wall. A hollow sound means the render has lost its bond. Loose areas need to be cut out back to sound render and replaced. Large or widespread drummy areas usually mean a full re-render is more economical.
Cracks with a cause behind them: remediate first
Stepped or diagonal cracks from window corners, cracks with rust staining, or render pushed off over lintels point to movement, corroding steel or water behind the wall. Re-rendering over those problems fails quickly. See cracked render: causes and repairs.
Signs the problem is behind the render
- Rust stains bleeding through cracks.
- Cracks that return after previous patching.
- Damp or salt staining at the base of walls.
- Cracks in the same places inside the building.
How render repairs are done properly
- Identify and fix the cause: water, movement, lintels or concrete cancer.
- Remove loose and drummy render back to sound material.
- Repair the substrate: brickwork, concrete or blockwork.
- Re-render with a mix compatible with the wall. Softer, breathable render suits older masonry.
- Finish with a suitable coating system.
Render and facade repairs in Sydney
See our facade and render repair service, or send us photos and we will tell you which of the three situations you are in.
Frequently asked questions
How do I know if render is drummy?
Tap it with a knuckle or handle. A hollow sound means the render has lost its bond with the wall behind.
Can I patch cracked render?
Fine, well-bonded cracks can be patched. Drummy render or cracks caused by movement or corrosion need the cause fixed and the render replaced.
Why does my render keep cracking after repairs?
Usually because the cause behind it, such as water, movement or rusting lintels, was never fixed.
