Brisbane Pool Repair Guide

SPIDER CRACKS VS
STRUCTURAL CRACKS

Not all pool cracks are the same. Knowing the difference between cosmetic spider cracking and genuine structural cracking can save you unnecessary worry, or help you catch a real problem early.

Quick Rule
of Thumb

Spider cracks are fine, web-like, and confined to the surface. Structural cracks are wider, deeper, and often come with other warning signs like water loss or movement.

Spider cracks are common and usually cosmetic
Structural cracks indicate a deeper issue and need proper assessment
Water loss and visible movement are the clearest signs something is structural
When in doubt, getting it checked is faster than guessing

Understanding which type you're dealing with helps you respond appropriately, without overreacting to something cosmetic or ignoring something that needs attention.

What Are Spider Cracks?

Spider cracks, sometimes called crazing, are fine, web-like hairline cracks that form in the gelcoat surface of a fibreglass pool. They're extremely common, particularly in older pools or those that have seen years of sun and chemical exposure, and they typically don't extend beyond the thin outer gelcoat layer.

While not a structural concern, spider cracks are still worth addressing, since an open crack in the gelcoat can allow water to seep behind the surface over time, which can lead to other issues like blistering or delamination if left unaddressed.

What Are Structural Cracks?

Structural cracks extend beyond the gelcoat surface into the fibreglass shell itself. These are a more serious matter, generally caused by ground movement, hydrostatic pressure, or stress on the pool's structure, and they often come with other signs beyond just the visible crack itself.

Unlike spider cracks, structural cracks can affect the pool's ability to hold water properly and, in more severe cases, its overall structural integrity.

How to Tell Them Apart

Appearance
Spider cracks form a fine, web-like or branching pattern across the surface. Structural cracks tend to be a single, more defined line, often wider and sometimes following a straighter path.
Depth
Spider cracks are confined to the gelcoat surface. Structural cracks extend into the fibreglass shell underneath.
Associated symptoms
Spider cracks generally appear in isolation, with no other issues. Structural cracks are often accompanied by water loss, bulging, doming, or a sense of movement in the pool wall or floor.
Behaviour over time
Spider cracks tend to stay relatively stable once they appear. Structural cracks often grow or worsen over time if the underlying cause isn't addressed.

Why This Distinction Matters for Repair

Spider cracks are usually addressed as part of a surface-level repair or resurfacing, since they're cosmetic, the urgency is lower and the fix is more straightforward. Structural cracks need the underlying cause properly identified and addressed, simply filling the visible crack without understanding why it formed risks the same problem recurring.

This is also relevant for insurance purposes in some cases, since the cause of a structural crack (sudden ground movement versus gradual deterioration, for example) can affect how a claim is assessed.

When to Get a Professional Assessment

If you're not confident whether a crack is spider cracking or something deeper
If you're noticing water loss beyond normal evaporation
If there's any visible bulging, doming or movement
If a crack is growing, widening or reappearing after a previous repair

Frequently Asked Questions

Do spider cracks mean my pool needs resurfacing?
Not necessarily. Isolated spider cracking can often be addressed with a targeted repair. Widespread spider cracking across the whole pool surface is more likely to benefit from full resurfacing.
How can I tell if a crack is going deeper than the surface?
Structural cracks tend to be wider and more defined than the fine, web-like pattern of spider cracks, and are often accompanied by other signs like water loss or movement. A professional assessment can confirm which you're dealing with.
Can a structural crack get worse if I don't address it?
Yes. Structural cracks often continue to be affected by the same underlying cause, whether that's ground movement or pressure, which means they can widen or worsen over time if left unaddressed.
Is it normal for an older pool to have some spider cracking?
Yes, spider cracking becomes more common as a fibreglass pool ages, particularly with years of sun and chemical exposure. It's still worth addressing to maintain a sealed surface, but it's not unusual.

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Disclaimer: The information on this page is general guidance only and is not a substitute for a professional inspection or repair assessment. Pool construction, age, prior repairs and surrounding ground conditions can vary significantly. If you notice structural cracking, water loss or movement, consult a qualified pool repair professional before relying on self-checks alone.