What Causes Cracks in Swimming Pool Surfaces?

Cracks in a swimming pool can appear for several reasons, ranging from construction problems to changes in the ground surrounding the pool.

Some cracks may only affect the finish, while others can point to movement or pressure affecting the pool structure. This article goes over the common issues that can cause pool surfaces to develop cracks.

Common Causes of Cracks in Swimming Pool Surface

Understanding the causes of cracks in swimming pool surface can help property owners determine why damage is appearing and what may need to be inspected.

A swimming pool is exposed to water pressure, changing temperatures, soil movement, and regular use throughout its life.

The pool shell, surrounding deck, plumbing, and soil all need to work together to keep the structure stable.

Not every crack develops for the same reason. A small surface crack may be related to the plaster or finish, while a larger or expanding crack may involve the pool shell or movement beneath it.

The location, width, depth, and pattern of a crack can provide important clues about what is happening beneath the visible pool surface. A professional inspection can help determine if the problem is mainly cosmetic or requires more extensive repairs.

Poor Workmanship During Pool Construction

The quality of the original construction can have a major effect on how well a swimming pool holds up over time. Cracks in swimming pool surface may develop when the pool shell, reinforcement, concrete, plaster, or other materials are not installed correctly.

Problems can also occur when construction steps are rushed or materials are applied under unsuitable conditions.

Proper preparation and installation are important because a swimming pool must continuously withstand significant pressure from both the water inside it and the ground surrounding it.

For example, incorrect concrete placement, inadequate reinforcement, poor surface preparation, or improperly applied plaster can create weak areas.

These weaknesses may not always be visible immediately after construction, but they can become noticeable as the pool ages and experiences normal environmental stresses.

Timing can also matter during construction. Concrete and other cement-based materials need appropriate conditions to cure and develop strength. If materials dry too quickly, are mixed incorrectly, or are placed without proper preparation, small weaknesses may form.

Over time, those areas can become more noticeable as the pool goes through temperature changes and repeated cycles of filling, use, and maintenance.

Excessive Water Pressure Around the Pool Shell

Water does not only create pressure from inside a swimming pool. Groundwater can also build up outside and underneath the pool shell.

When that happens, cracks in swimming pool surface can develop if the surrounding water creates forces that the structure cannot properly handle. Drainage conditions around the property can therefore play an important role in protecting the pool.

Heavy rainfall, poor yard drainage, a high water table, or damaged drainage systems can allow water to collect in the soil surrounding the pool.

When water remains trapped around the pool structure, the pressure against the shell can increase and place additional stress on vulnerable areas.

The problem can become more serious when a pool is drained because there is no longer a large volume of water inside the pool helping to counter pressure from below.

For this reason, draining an in-ground swimming pool is not always a simple maintenance task. Conditions below and around the structure may need to be considered first.

Proper drainage systems and professional evaluation can reduce the risk of damage when groundwater is known to be an issue on the property.

Shifting Soil Beneath the Swimming Pool

A swimming pool depends heavily on the stability of the soil supporting it. Cracks in swimming pool surface can appear when that soil settles, expands, contracts, washes away, or otherwise changes after construction.

Even a strong pool shell can experience stress when different sections of the ground beneath it begin moving at different rates.

Several conditions can contribute to soil movement. Certain soils expand when they absorb moisture and shrink when they dry, while poorly compacted fill can gradually settle under the weight of the pool.

Plumbing leaks and drainage problems may also change moisture levels in the surrounding ground.

Uneven soil movement can place concentrated stress on parts of the pool shell instead of allowing the structure to remain evenly supported.

Signs of soil movement may sometimes appear in other areas of the property as well. Pool decking may become uneven, gaps can develop around nearby surfaces, or cracks may continue growing after an earlier repair.

Identifying the underlying soil problem is important because repairing only the visible pool finish may not prevent the damage from returning.

Excessive Water Pressure Around the Pool Shell

Pressure problems can also occur when water repeatedly enters areas around the pool through irrigation, runoff, or pool leaks, or poor grading.

In these situations, cracks in swimming pool surface may be connected to ongoing moisture conditions rather than a single period of heavy rain.

Water can slowly change the condition of surrounding soil and affect how evenly the pool is supported.

A drainage problem that seems minor at ground level can become more significant when water repeatedly collects near the pool foundation.

Sprinklers that continually saturate one area, leaking underground pipes, or landscaping that directs runoff toward the pool can gradually create uneven moisture levels. Some soil may soften or shift while other areas remain relatively dry and stable.

Finding the source of the moisture is an important part of addressing this type of problem. Simply filling a visible crack may improve its appearance without correcting the condition that contributed to it.

Checking drainage, plumbing, irrigation, and grading can provide a broader picture of why water is collecting around the structure and whether additional repairs are needed.

Improper Expansion Joint Installation Around the Pool

Swimming pools and the decks surrounding them are separate structures that can move differently as temperatures and ground conditions change. An expansion joint provides space between these areas so normal movement does not force the deck directly against the pool.

Cracks in swimming pool surface may develop when this joint is missing, incorrectly installed, damaged, or no longer able to provide enough separation.

Concrete naturally expands and contracts as temperatures change. The pool deck may also move because of soil conditions, moisture, or settling.

Without enough separation, that movement can transfer pressure to the coping or pool structure. Damage may then become visible near the upper portion of the pool, along the tile line, around coping, or in nearby finished surfaces.

A properly designed and maintained expansion joint gives surrounding concrete room to move without placing unnecessary pressure on the pool itself.

Joint materials can deteriorate with age and exposure to sunlight, water, chemicals, and changing weather conditions, so older joints may eventually require attention.

When cracking appears near the point where the deck and pool meet, the expansion joint is one area that should be examined.

Repairing damaged joint material and addressing movement in the surrounding deck may help prevent additional stress, while more serious cracking may require an evaluation of the pool shell and nearby structural components during pool remodeling.