What Causes Pool Plaster To Crack?

Seeing cracks in your pool plaster can be alarming. Some cracks are cosmetic and minor — others are a sign of a real problem that needs attention. Here's what causes pool plaster to crack and what you should do about it.

1. Age The most common cause of cracking is simply age. Plaster has a lifespan of 7–10 years under normal conditions. As it gets older it becomes brittle and more susceptible to cracking from normal use and temperature changes.

2. Improper Water Chemistry Water that's too aggressive — low pH, low calcium hardness, or high chlorine — will actually eat away at your plaster from the inside. This is called etching and over time it weakens the surface and leads to cracking and pitting.

3. Ground Movement California is earthquake country and even minor ground shifts can cause structural cracks in a pool shell. These are more serious than surface cracks and should be inspected by a professional as soon as possible.

4. Poor Original Workmanship Plaster that was applied incorrectly, too thin, or without proper curing can crack prematurely. This is why hiring a licensed contractor matters — a C-53 licensed pool contractor knows exactly how plaster should be mixed, applied and cured.

5. Freeze and Thaw Cycles Less common in Fresno but worth mentioning — pools in areas with cold winters can experience cracking from water freezing and expanding inside the plaster. Central Valley pools are mostly spared from this but elevation properties can be affected.

6. Dewatering The Pool Draining your pool completely without doing it properly or at the right time of year can cause the plaster to dry out and crack. Always consult a professional before draining your pool.

When Should You Be Worried? Hairline cracks that don't leak are usually cosmetic. Cracks that are spreading, wide enough to fit a coin in, or causing water loss need professional attention immediately.

Think your pool plaster is failing? Allegiant Pool offers free on-site assessments throughout Fresno and the Central Valley. Call 559-283-7697 today.