When a homeowner or buyer sees a crack in a swimming pool, it is easy to jump straight to the worst possible conclusion. With all the recent attention surrounding “concrete cancer” in Central Texas pools, even a small mark in the plaster can suddenly feel like evidence of a major structural failure.
TLDR: Signs That May Justify a Closer Pool Evaluation
- Map-like or irregular cracking can be associated with ASR, but cracking alone does not confirm it.
- Cracks that repeatedly return after cosmetic repair deserve more attention than a stable surface mark.
- Expansion, displacement, joint movement, bulging, or separation may indicate internal pressure or another structural problem.
- White or brown deposits and damp-looking discoloration may occur near ASR cracks, but they can also have other causes.
- A qualified pool professional, engineer, or materials specialist may need to inspect and test the concrete before anyone can identify the cause.
What Does ASR Damage Usually Look Like?
The Federal Highway Administration identifies map cracking as one of the classic outward symptoms of alkali-silica reaction in unrestrained concrete. It also explains that crack patterns may change when concrete is restrained by reinforcing steel or surrounding structural elements. In restrained concrete, cracking may appear more aligned with the direction of the reinforcement or principal stresses rather than forming a perfect map pattern.
A swimming pool shell is not an unrestrained slab sitting by itself. It contains reinforcing steel and is surrounded by soil, decking, plumbing, coping, tile, and other materials. Because of that, a pool may not display every textbook symptom in a neat or obvious way.
The following conditions are best understood as warning signs. They are reasons to investigate, not permission to declare that a pool has concrete cancer.
1. Map-Like or Alligator Cracking
Map cracking is a network of irregular, interlocking cracks that may resemble a road map, dried mud, or alligator skin. The cracks may branch in several directions and create small, uneven shapes across the surface.
This pattern is often associated with internal expansion occurring in multiple directions. However, surface finishes can also develop crazing or shrinkage patterns that look similar from a distance. A professional needs to determine whether the cracking is confined to plaster or extends into the concrete shell.
A photograph taken from across the pool may make shallow plaster crazing look severe, while a close inspection may reveal that it is limited to the finish. The opposite can also happen. A narrow-looking crack may continue through the shell and represent a more significant concern.
2. Long Cracks That Appear Aligned
ASR-related cracking does not always look like a random map. Reinforcing steel and other restraints can influence where the concrete relieves internal pressure. As a result, cracks may appear in longer, more consistent lines that follow structural directions.
In a pool, aligned cracking may appear along walls, steps, benches, transitions, or other portions of the shell. It may also appear near areas where different structural components meet.
Aligned cracks can have many causes, including settlement, soil movement, poor construction joints, or inadequate reinforcement. Their direction and location may help a qualified evaluator understand the forces affecting the pool, but the pattern does not identify the cause by itself.
3. Cracks That Return After Cosmetic Repair
A crack that has been patched once and remains stable may tell a different story from a crack that repeatedly reopens, widens, or spreads after repair. When the underlying concrete continues moving or expanding, a surface patch may temporarily improve the appearance without stopping the process.
Repeated repairs are particularly important in a real estate transaction because a freshly resurfaced pool can look beautiful while the history tells a more complicated story. Buyers should ask for repair invoices, warranties, photographs, engineering reports, and any communications that explain why the work was performed.
Sellers should preserve those records rather than assuming the current appearance tells the whole story. A documented history helps everyone evaluate whether the prior work was cosmetic, structural, preventative, or part of an ongoing problem.
4. Cracks Extending Beyond the Plaster Finish
Pool plaster is a finish layer. It can develop stains, checking, crazing, etching, delamination, and cracks for reasons unrelated to structural failure. The concern becomes greater when cracking appears to continue through tile, coping, steps, the bond beam, or the pool shell itself.
A pool professional may need to determine whether the visible crack stops at the surface or represents movement in the underlying structure. That evaluation may involve sounding the finish, examining accessible portions of the shell, reviewing water-loss patterns, or recommending more specialized investigation.
The distinction matters because refinishing a pool and repairing a structural shell are very different projects with very different costs, timelines, and risks.
5. Expansion, Bulging, or Distortion
ASR can cause concrete to expand. In an affected structure, that expansion may lead to displacement, distortion, extrusion at joints, or misalignment between connected elements.
In and around a pool, a homeowner might notice areas that appear to bulge, shift, lift, bow, or move out of alignment. Tile lines may no longer appear straight. Coping may separate. Steps or benches may show unusual cracking or movement. Deck joints may close, widen, or become uneven.
These conditions can also result from expansive soils, drainage problems, settlement, tree roots, plumbing leaks, or construction deficiencies. Regardless of the cause, visible movement deserves professional evaluation because it may affect more than appearance.
6. Separation at Tile, Coping, Decking, or Joints
A pool is a system made of materials that move differently. The shell, coping, deck, tile, plumbing, and surrounding soil experience temperature changes, moisture, settlement, and loading. Proper joints and construction details allow those materials to move without damaging one another.
When internal expansion or structural movement occurs, connected components may begin separating or pressing against one another. Signs may include broken tile, opened joints, lifted coping, compressed sealant, uneven decking, or cracks where the shell and surrounding improvements meet.
One separated tile is not evidence of concrete cancer. A pattern of movement across several connected areas, especially when it continues progressing, is more significant and should be documented carefully.
7. White, Clear, or Gel-Like Deposits Near Cracks
ASR can produce gel that moves into cracks, pores, and voids within the concrete. In some cases, material may appear at the surface near cracking.
However, surface deposits do not automatically prove ASR. Water moving through concrete can also carry dissolved minerals and leave efflorescence. Pool chemicals, calcium scale, grout deterioration, and moisture migration may produce deposits that look similar to someone without materials-testing experience.
The Federal Highway Administration specifically cautions that surface deposits can result from mechanisms other than ASR. A specialist may need to examine or test the material before identifying what it is.
8. Brown or Persistently Damp-Looking Discoloration
Some ASR-affected cracks may appear bordered by brown discoloration or a zone that looks persistently damp. Moisture moving through cracked concrete can transport reaction products, minerals, rust, or other material toward the surface.
Discoloration can also come from metals in the water, organic matter, soil, irrigation, waterproofing failure, rusting components, or ordinary staining. The location of the stain, whether it returns after cleaning, and whether it follows a crack may help guide further investigation.
9. Unexplained Water Loss
Water loss does not diagnose ASR, but it can be an important symptom when combined with structural cracking. Pools lose water naturally through evaporation, splash-out, and maintenance. A leak becomes more likely when the water level drops faster than expected or consistently stops at a particular elevation.
A leak-detection professional can help determine whether water is escaping through plumbing, fittings, skimmers, lights, tile lines, or the shell. If the shell is leaking through cracks, the next question becomes why those cracks developed.
Buyers should not accept “it is probably evaporation” when the available evidence suggests otherwise. Sellers should also address unexplained water loss before listing when possible because a buyer’s inspector is likely to notice it.
10. Progressive Change Over Time
One of the most useful clues is not a particular crack shape, but change. ASR is generally discussed as a progressive deterioration process. Cracks may widen, branch, reappear, or affect additional areas as expansion continues.
Homeowners can help professionals by maintaining dated photographs, noting water-loss changes, preserving repair records, and measuring significant cracks when advised by an engineer. The Federal Highway Administration recognizes crack mapping as a useful visual tool for tracking deterioration and expansion over time.
Do not mark or measure a pool in a way that damages the finish or creates a safety problem. The point is to preserve reliable information, not to conduct your own engineering investigation.
What Conditions Can Look Like Concrete Cancer?
Several common pool problems can create symptoms that overlap with ASR. These include:
- Plaster crazing, checking, etching, or delamination
- Concrete drying shrinkage
- Expansive soil movement or settlement
- Poor drainage around the pool
- Plumbing leaks that wash out or soften supporting soil
- Hydrostatic pressure
- Improperly constructed joints
- Inadequate reinforcement or workmanship
- Corrosion of embedded metal
- Ordinary efflorescence or mineral scale
- Tree roots or movement in adjacent decking
This is why online photographs and checklists have limits. Even when the symptom is real, the wrong diagnosis can lead to the wrong repair. Covering a structural crack with new plaster will not solve the movement. Demolishing a pool because of ordinary surface crazing would be equally unreasonable.
When Should a Buyer or Homeowner Call a Specialist?
A specialist should be considered when cracking appears structural, progressive, widespread, recurrent, associated with water loss, or accompanied by movement in coping, tile, decking, steps, or the shell.
A reasonable sequence may include:
- A qualified pool professional familiar with structural pool concerns
- Leak detection when unexplained water loss is present
- A licensed professional engineer when structural movement is suspected
- A concrete materials specialist or petrographer when ASR is a reasonable possibility
- Core sampling and laboratory testing when recommended
A general home inspector remains an important part of the buying process, but the inspector may properly recommend additional expertise rather than attempt to diagnose a specialized concrete condition. My guide to choosing the right home inspector explains why the inspector’s experience, scope, and referral judgment matter.
What Should Buyers Ask During a Real Estate Transaction?
When a home has a pool, buyers should review more than the water color and landscaping. Useful questions include:
- When was the pool constructed?
- Who built it?
- Has the pool ever leaked, cracked, shifted, or required structural repair?
- Has it been replastered, and why?
- Are there engineering, testing, inspection, or leak-detection reports?
- Have any insurance claims or warranty claims been made?
- Are repair warranties transferable?
- Have cracks returned after prior repairs?
Buyers should also understand that specialized testing may take longer than a typical option period. The real estate broker, inspector, engineer, lender, insurance professional, and attorney may need to help the buyer understand what can realistically be determined before contractual deadlines expire.
What Should Sellers Do When They Notice These Signs?
A seller should not diagnose the condition without qualified support, but the seller should not hide or cosmetically cover known concerns either. Gather records, photograph the condition, obtain appropriate evaluation, preserve reports, and answer disclosure questions based on actual knowledge.
Texas REALTORS reported that Alkali-Silica Reaction, also known as concrete cancer, was added to Section 3 of its revised Seller’s Disclosure Notice due to the increasing prevalence of the condition. Sellers who are uncertain about a legal disclosure obligation should consult an attorney rather than relying on a contractor, buyer, or real estate license holder for legal advice.
For broader guidance, read What to Disclose When Selling a Home.
Frequently Asked Questions About Signs of Pool Concrete Cancer
Does map cracking always mean ASR?
No. Map cracking is a classic possible indicator, but similar-looking patterns can occur in finishes and concrete for other reasons.
Can new plaster hide concrete cancer?
New plaster can cover visible cracking temporarily, but it does not necessarily stop movement or expansion in the underlying shell. Buyers should ask why the pool was resurfaced and request the related records.
Are white deposits around a crack ASR gel?
Possibly, but they may also be efflorescence, calcium scale, or other minerals. A professional may need to examine or test the deposit.
Is a leaking pool proof of ASR?
No. Plumbing, fittings, skimmers, lights, tile lines, and ordinary cracks can all leak. Leak detection may identify where water is escaping, but additional evaluation may be needed to determine why the failure occurred.
Can a home inspector diagnose concrete cancer?
A home inspector may identify suspicious conditions and recommend additional evaluation. A reliable ASR diagnosis may require engineering, petrographic, or laboratory analysis.
My Bottom Line
The most common signs of concrete cancer in a pool may include map-like cracking, aligned cracks, recurrent cracking, expansion, separation, deposits, discoloration, water loss, and progressive movement. None of those observations should be ignored, but none should be treated as a diagnosis by itself.
The best decision comes from understanding the pattern, history, progression, and underlying cause. Buyers and sellers deserve facts, not panic. When a question moves beyond the limits of a visual inspection, the right next step is a qualified pool professional, engineer, or concrete materials specialist.
If you are buying or selling a home with a pool in the Greater Austin Area, I will help you organize the real estate side of the evaluation, protect the important transaction deadlines, and bring the right professionals into the conversation when needed.
Sources and Further Reading
- Federal Highway Administration: Alkali-Silica Reactivity Field Identification Handbook
- Federal Highway Administration: Alkali-Silica Reaction and Typical Damage Patterns
- Federal Highway Administration: Protocol for Evaluating ASR-Affected Structures
- American Society of Civil Engineers: Concrete Cancer and the Central Texas Pool Crisis
- Texas REALTORS: 2026 Forms Updates
