What Causes Roof Tiles to Crack? 7 Common Reasons

11 min read

Finding a cracked tile on your roof isn’t unusual - it happens to most tile roofs eventually. But the reason it cracked matters far more than the crack itself. A tile broken by a falling branch is a simple repair. Tiles cracking due to thermal stress or foundation movement could be a sign of a systemic problem that will keep producing cracks until the underlying cause is addressed.

We handle roof repair and replace cracked tiles on Perth roofs every week. Here are the seven most common causes we see, how to identify each one, and what to do about it.

1. Thermal Cycling

This is the number one cause of tile cracking in Perth, and it’s entirely driven by our climate.

What happens: Perth regularly sees temperature swings of 20-30 degrees in a single day. In summer, roof tiles can reach 65-75°C in the afternoon sun, then cool to 20-25°C overnight. In winter, tiles might go from near-freezing overnight to 25°C by midday.

Every time a tile heats up, it expands. Every time it cools, it contracts. This thermal cycling happens every single day, 365 days a year. Over thousands of cycles, the repeated expansion and contraction creates microscopic stress fractures in the tile body. Eventually, those micro-fractures join up and the tile cracks.

How to identify it: Thermal stress cracks typically run in a relatively straight line across the tile, often roughly perpendicular to the direction of the tile’s length. They tend to appear on the most sun-exposed parts of the roof - north and west-facing planes. You’ll often see multiple tiles affected in the same area, not just one isolated crack.

Is it systemic? Yes. If thermal cycling is cracking tiles, it will continue to crack more tiles over time. The rate depends on the tile quality, age, and exposure. A few cracks per year on an older roof is manageable with periodic tile replacements. Dozens of cracks appearing rapidly suggests the tiles are reaching the end of their useful life.

What to do: For isolated thermal cracks, replace the affected tiles. For widespread cracking, get a full roof assessment to determine whether restoration (with tile replacement as needed) or full roof replacement is the better path.

2. Foot Traffic

People walking on a tile roof is one of the most common causes of cracked tiles - and one of the most preventable.

What happens: Concrete and terracotta tiles are designed to withstand the loads they experience in normal service - rain, wind, their own weight, and the occasional possum. They’re not designed for concentrated point loads from a person’s weight applied through a boot sole.

Tiles are strongest at their supported points - where they rest on the battens. They’re weakest in the unsupported spans between battens. Step on the wrong part of a tile and it snaps.

How to identify it: Foot traffic cracks are usually clean breaks - the tile snaps in half or cracks across the unsupported span. Look for boot scuff marks on nearby tiles and the pattern of cracks following a walking path across the roof. Common around TV antennas, air conditioning units, solar panels, and anywhere that requires roof access for maintenance.

Is it systemic? No - unless someone keeps walking on the roof the wrong way. Each crack is caused by a specific footstep, not an ongoing structural problem.

What to do: Replace the cracked tiles. More importantly, make sure anyone who needs to access your roof (antenna installers, aircon technicians, solar panel cleaners, gutter cleaners) knows how to walk on tiles properly - stepping on the lower third of the tile where it’s supported by the batten, never on the centre span. Better yet, use a qualified roofer who knows how to move across a tile roof without causing damage.

3. Impact Damage

Perth’s storm season delivers hail, fallen tree branches, and windborne debris that can crack or shatter tiles.

What happens: A falling branch or large hailstone hits the tile with enough force to exceed its impact strength. The tile cracks, chips, or in severe cases, shatters completely.

How to identify it: Impact damage usually looks different from other types of cracking. You’ll see:

• Hail damage: Small circular chips or cracks, often in the centre of the tile face. Multiple tiles affected across the roof. The damage pattern matches the direction the hail was falling.
• Branch damage: Larger, more irregular cracks or complete breaks. Usually localised to the area where the branch fell. You might see scratches and displacement of nearby tiles as well.
• Windborne debris: Similar to hail but often limited to one side of the roof (the windward face during the storm).

Is it systemic? No - impact damage is caused by specific events, not ongoing deterioration. However, if your property has overhanging trees, branch impact will recur unless the trees are trimmed back.

What to do: Replace damaged tiles. Document the damage for insurance if it was caused by a storm event. Trim overhanging branches to prevent recurrence.

4. Manufacturing Defects

Not all tiles are created equal, and some batches leave the factory with problems that don’t become apparent for years.

What happens: During the manufacturing process, concrete tiles can develop internal weaknesses from:

• Inadequate curing - if the tiles weren’t cured at the correct temperature and humidity for the required duration, the concrete doesn’t reach full strength
• Incorrect mix ratios - too much or too little water, cement, or aggregate
• Air pockets - voids trapped in the tile body during pressing that create stress concentration points
• Surface coating defects - coatings that don’t bond properly, allowing moisture to penetrate the tile body

How to identify it: Manufacturing defects typically show up as unusual cracking patterns that don’t match any other cause. Tiles might crumble rather than crack cleanly. The tile body might appear soft, chalky, or layered when you look at the broken edge. Multiple tiles from the same batch (installed at the same time) show similar problems.

If a large number of tiles on a relatively young roof (under 20 years) are cracking without explanation, manufacturing defect is worth investigating.

Is it systemic? Yes - if the batch was defective, all tiles from that batch share the same weakness. The failure rate will increase over time as the defect worsens.

What to do: If you suspect a manufacturing defect, document the damage and contact the tile manufacturer. Tile manufacturers offer warranties (typically 50 years for concrete tiles), and a legitimate defect may be covered. You’ll need proof of the tile type and installation date - your original building contract or council records may have this information.

5. Age Deterioration

Every tile has a finite lifespan. Concrete tiles typically last 40-60 years, and terracotta tiles can last 70-100+ years with good maintenance. But all tiles degrade over time.

What happens: The concrete in concrete tiles slowly breaks down through a process called carbonation - carbon dioxide from the atmosphere reacts with the calcium hydroxide in the concrete, changing its chemical structure and gradually weakening it. This process is accelerated by moisture, heat, and UV exposure (all of which Perth delivers in abundance).

Over decades, the tile body becomes more porous, less flexible, and more brittle. Tiles that once could withstand thermal cycling and minor impacts without cracking become fragile and prone to failure.

How to identify it: Age-related deterioration is gradual and widespread. Signs include:

• Tiles that crumble or break easily when handled
• Surface erosion - the aggregate is visible through the worn coating
• The tile body feels soft or chalky
• Increasing numbers of cracks appearing across the whole roof, not just one area
• Tiles absorbing water visibly (they darken when wet and stay dark for a long time)

Is it systemic? Yes - all tiles on the roof are the same age and experiencing the same deterioration. It’s a whole-of-roof problem that will only get worse.

What to do: For tiles approaching the end of their life, a full restoration (including a protective coating that reduces moisture absorption and UV exposure) can extend their service by 15-20 years. For tiles that are genuinely past it - crumbling, delaminating, or cracking under normal handling - replacement is the only option.

6. Poor Installation - Nails Too Tight

This one often goes unnoticed for years before it starts causing problems.

What happens: When tiles are installed, they’re nailed to the battens through a pre-formed hole in the tile. The nail should hold the tile firmly in place but allow a tiny amount of movement for thermal expansion. If the nail is driven too tight - hammered flush or even slightly below the tile surface - it pins the tile rigidly.

When the tile tries to expand in the heat, it pushes against the nail that’s holding it too tightly. Something has to give, and it’s usually the tile - a crack develops radiating out from the nail hole.

How to identify it: Look for cracks that start at the nail hole and radiate outward. The crack pattern often looks like a starburst or a single line running from the hole. If you lift the tile, the nail is tight against the tile surface or even slightly embedded.

This problem tends to show up after 10-15 years of thermal cycling, when the cumulative stress finally exceeds the tile’s strength around the nail hole.

Is it systemic? It can be. If the installer consistently over-drove nails (same person, same hammer technique, same section of roof), many tiles in that area may eventually crack. However, it’s also common to see isolated cases where a few nails were hit too hard.

What to do: Replace cracked tiles. For tiles that haven’t cracked yet but show signs of stress around the nail hole (hairline cracks starting to form), a roofer can loosen the nail slightly to relieve the pressure - though this requires care to ensure the tile remains adequately secured.

7. Foundation Movement

Perth is built on some of the most reactive soils in Australia. When the ground moves, the house moves - and the roof moves with it.

What happens: Reactive clay soils (common across Perth’s eastern suburbs, some southern suburbs, and much of the Swan Coastal Plain) swell when they absorb moisture and shrink when they dry out. This seasonal movement causes subtle shifts in the house’s foundation, which translate up through the walls and into the roof frame.

When the roof frame moves - even a few millimetres - it can put stress on tiles in unexpected ways. Tiles that were sitting flat are now slightly twisted or flexed. Over time, this stress causes cracks.

How to identify it: Foundation-related tile cracking often has these characteristics:

• Cracks concentrated along one section of the roof, particularly near the junction of two different roof planes
• Tiles that appear to have shifted slightly out of alignment
• Cracking corresponds with visible signs of foundation movement elsewhere - cracks in walls (especially around doors and windows), doors that stick, gaps appearing between walls and floors
• The cracking pattern follows the line of roof stress, not random distribution

Foundation-related cracking may be seasonal - worse after a dry summer when the clay has shrunk, or after heavy winter rain when it swells.

Is it systemic? Yes - and it’s a symptom of a bigger problem. While the roof tiles can be replaced, they’ll keep cracking if the foundation continues to move.

What to do: Replace the cracked tiles, but also investigate the foundation movement. You may need:

• A geotechnical assessment of the soil conditions
• A structural engineer to assess the foundation and house frame
• Drainage improvements to manage moisture around the footings
• Foundation remediation in severe cases

Don’t ignore foundation-related cracking. The tile damage is the visible symptom - the structural movement affecting the house frame is the real concern.

One Crack vs. a Pattern

The most important thing when you find cracked tiles is to determine whether it’s an isolated incident or part of a pattern.

One or two cracked tiles after a storm, or in a spot where someone walked on the roof, is a simple repair. Replace the tiles and move on.

A pattern of cracking - especially if it’s spreading over time, concentrated in one area, or affecting tiles that shouldn’t be under any unusual stress - needs investigation. The cause matters more than the crack.

A professional roof inspection can identify the cause, assess the extent of the damage, and recommend whether you’re looking at a few tile replacements, a full restoration, or (in the worst case) a roof replacement.

The Bottom Line

Cracked tiles are a symptom, not a diagnosis. The crack tells you something went wrong - understanding what went wrong tells you whether it’s a minor repair or a warning sign of something bigger.

For Perth roofs, thermal cycling and foot traffic account for the majority of cracked tiles we see. Both are manageable with proper maintenance and care. But if you’re seeing increasing numbers of cracks, cracks in unusual patterns, or cracks combined with other signs of movement or deterioration, get a professional up there to look at the bigger picture.

A few replaced tiles now is far cheaper than ignoring a developing problem until it becomes a full roof replacement.