Roof Alligatoring: Detect, Reasons, Impacts, and Fixing

Written By Adam Paul - Waterproofing Expert

Roof alligatoring is a type of cracking pattern on the roofing layer that looks like the rough, dry skin of an alligator. Roof alligatoring is mostly visible on flat roofs. Mostly alligatored roofs are asphalt-based roofs, built-up roofing (BUR), modified bitumen roofs, and older flat roofs with asphalt coatings. roof aligatoring can be detected by cracking patterns, discoloration, loss of flexibility, peeling or blistering. 

The main causes for roof aligatoring are aging of roof materials, UV radiation, Poor roof maintenance, low-quality coatings, continuous water exposure over time, thermal expansion and contraction, and improper installation. Roof aligatoring impacts negatively on roofs by leaking water, losing waterproofing, decreasing insulation efficiency, accelerating roof deterioration, increasing energy bills, and increasing structural damage in the building. To prevent these negative impacts of roof aligatoring should be fixed properly. 

In order to prevent roof aligatoring home homeowners should use high-quality roofing, schedule maintenance, roof cleaning, ensure proper drainage, periodically recoat, control thermal movements, and fix minor issues promptly. By following proper methods and maintenance, roof aligatoring can be stopped successfully. A well-installed roofing can resist alligatoring for 10 to 20 years, depending on the material and environmental exposure. If you install a metal roof, clay tiles, slate roofing, PVC, and TPO, silicone-coated roofing will not alligator over time. 

As waterproofing experts, the Aqviz team has included so many important facts in this guide about roof alligatoring.

What is Roof Alligatoring?

Roof alligatoring is a type of cracking pattern on the roofing layer that looks like the rough, dry skin of an alligator. Roof alligatoring is mostly visible on flat roofs. Mostly alligatored roofs are asphalt-based roofs, built-up roofing (BUR), modified bitumen roofs, and older flat roofs with asphalt coatings.

Roof alligatoring is a clear sign that the roofing material, especially the coating or membrane, has aged, dried out, and lost its elasticity over time due to rain, snow, and UV light. Once this damage appears, it’s a warning flag that the roof is at the end of its service life or severely compromised over time.

How to Detect Roof Alligatoring?

Roof alligatoring can be detected by cracking patterns, discoloration, loss of flexibility, and peeling or blistering on the roofing. 

1. Cracking patterns: Discover cracking patterns on the roofing layer. You should look for a dry, scaly pattern on the roof surface that resembles reptile skin.
2. Discoloration: Identify the discoloration on the roofing layer. Check for dull, chalky, or faded areas on the roof that are often the first indicators of roof coating breaking down.
3. Loss of flexibility: Check the roofing layer for flexibility and elongation capability. If the roofing material feels brittle or starts flaking when touched, it can be a sign of roof alligatoring.
4. Peeling or blistering: Observe peeling or blistering on the roofing layer. When the surface begins to peel or form bubbles, it’s often a precursor to alligator cracks forming beneath.

Aqviz, we highly recommend homeowners perform seasonal roof checks or have a professional roof inspection, especially if your roof is nearing the 10-15 year mark.

What are the Causes for Roof Alligatoring?

Roof alligatoring occurs due to these 7 causes, such as aging of roof materials, UV radiation, Poor roof maintenance, low quality coatings, continuous water exposure over time, thermal expansion and contraction, and improper installation.

1. Aging roof materials: Roofing materials naturally dry out and lose flexibility over time. It causes roof alligatoring.  
2. UV radiation: Constant sun exposure breaks down roof coatings, and it accelerates the roofing cracks.
3. Poor roof maintenance:  Poor roof maintenance causes roof alligatoring due to trapped debris and water in the roof materials.
4. Low-quality coatings: Cheap or improperly applied roof coatings fail prematurely and crack under stress over time.
5. Water exposure: Continuous water pooling or leakage degrades the roofing and creates alligatoring surfaces quickly.
6. Thermal cycling: Repeated roofing expansion on hot days and contraction on cold nights stresses the roof surface.
7. Improper roofing installation: Inexperienced roofing installation can cause roof alligatoring over time.

What are the Impacts of Roof Alligatoring?

Roof alligatoring impacts negatively on roofs by leaking water, losing waterproofing, decreasing insulation efficiency, accelerating roof deterioration, increasing energy bills and increasing structural damages in the building.

1. Water leaking from the roof: Roof alligatoring makes cracks in the surface and creates entry points for moisture, causing interior damage.
2. Loss of roof waterproofing:  Roof alligatoring minimizes the waterproofing capability of the roofing. It causes to prevents water from repel effectively through the roofing.
3. Decrease roof insulation efficiency: Roof alligatoring can lead to gaps that reduce the roof’s thermal performance over time.
4. Accelerate roof deterioration: Roof alligatoring increases the roofing deterioration when the coating is cracked.
5. Increased energy bills: Roof alligatoring can damage insulation and ventilation layers which can drive up heating and cooling costs in the house.
6. Structural damage risk: Prolonged roof alligatoring can leak water and moisture that can weaken the roof deck and supports.
7. Reduced property value:  Roof alligatoring reduces property value by increasing water and thermal damage in the house. 

A roof can be damaged by other roof problems, such as roof blistering, ceiling cracks and roof seepage. So you should be aware all of these problems before fix the roof damages.

How to Fix Roof Alligatoring?

You can fix roof alligatoring by following 8 steps.

1. Inspect the roof damage: Start with a thorough roof inspection to assess the extent of the cracking and check for deeper issues like moisture intrusion.
2. Clean the roof surface: Remove debris, dust, and old flaking material on the roof by using a pressure washer or stiff brush to ensure proper adhesion.
3. Cut out damaged roofing area: Cut out and remove the alligatoring roofing area. After that, clean the cutout area and fix all the substrate problems that cause roof alligatoring.
4. Repair minor cracks: Repair minor cracks on the roof for alligatoring. You can apply a high-quality elastomeric patching compound to fill in cracks and seal weak spots.
5. Replace damaged roofing sections: Replace the damaged roofing sections with new ones after the surface is properly prepared.
6. Apply roof primer: Apply roof primer to bond the roofing with the roof substrate. 
7. Recoat with elastomeric roof coating: Apply a UV-resistant, flexible coating designed to withstand expansion, contraction, and weather stress on the roofs.
8. Inspect and maintain the roof: After curing, do a final check and set up a roof maintenance schedule to monitor performance periodically.

We always recommend homeowners consult professionals like us at Aqviz, especially when dealing with larger flat roofs or aging materials.

How to Prevent Roof Alligatoring?

Roof alligatoring can be prevented by using high-quality materials, scheduled maintenance, roof cleaning, ensuring proper drainage, periodically recoating, controlling thermal movements, and fixing minor issues promptly.

1. Use high-quality coatings: High-quality roofing materials and coatings prevent roof alligatoring due to their higher UV resistance and flexibility.
2. Schedule regular roof inspections: You should inspect your roof for alligatoring at least once a year and after major storms.
3. Clean the roof surface: You should clean the roof surface by removing the dirt, algae, and debris that cause to trap moisture and increase the alligatoring over time.
4. Ensure proper drainage on roof: Proper drainage helps to prevent water standing on the roofing. That helps to prevent roofing d over time.
5. Control thermal movement: Use breathable roof coatings and proper insulation roofing membranes to reduce stress from temperature swings.
6. Recoat the roofing periodically: Recoat the roofing every 5-7 years. It helps to keep your roof protected and flexible without any alligatoring problems.
7. Fix minor roof issues: Fix small roof cracks or damage as soon as they appear to avoid bigger problems later.

Can Roof Waterproofing Stop Alligatoring?

Yes, roof waterproofing can absolutely help stop or delay roof alligatoring when it is done proactively and correctly. A high-quality, UV-resistant, and flexible waterproofing system can preserve a roof’s elasticity and prevent cracking patterns from forming over time.

Which Roofing is Alligatoring Mostly?

Alligatoring tends to affect asphalt-based roofing systems the most. These include:

• Built-Up Roofs (BUR)
• Modified Bitumen Roofing
• Asphalt shingles
• Old elastomeric coatings on flat roofs
  

These materials are prone to drying out, especially under intense sun and temperature swings. Flat roofs are especially vulnerable due to poor drainage, which keeps the surface wet longer and speeds up degradation.

How Long Can a Roofing Material Withstand Without Alligatoring?

A well-installed and maintained roof can resist alligatoring for 10 to 20 years. It depends on the roofing material and environmental exposure. Here’s a general breakdown based on our field experience:

• Asphalt shingles: ~15 years before early signs if unmaintained
• Modified bitumen: 10-12 years without recoating
• Elastomeric-coated flat roofs: 8-10 years before reapplication is needed
• High-end coatings (e.g., silicone or acrylic): Up to 20 years with proper maintenance

Which Roofing is Not Alligatoring?

Roofing such as metal, clay or tile, slate, PVC or TPO, and silicone coated roofing are not alligatoring even when they are dry and wet continuously.

• Metal roofing: Aluminum, steel, and copper roofs don’t crack like asphalt and can last decades without surface degradation.
• Clay or concrete tiles: Clay and concrete tiles are rigid but don’t contain oils that dry out and crack like asphalt does.
• Slate roofing: Slate roofing is a durable, natural stone that resists UV damage and doesn’t develop alligatoring patterns.
• PVC or TPO membranes: PVC and TPO membranes are designed to be UV-stable and flexible, minimizing the risk of roof aligatoring over time.
• Silicone-coated roofs: High-quality silicone coatings resist roof cracking and hold up well under extreme sun exposure.

Read more about: 12 Types of Roof Shingles

Which Part of the Roof is Mostly Alligatoring?

Roof alligatoring can be visible mostly on stressed and frequently exposed to water and sunlight areas over time. Aqviz experts have investigated this as we found the below 5 areas are the mostly impacted by the roof alligatoring. 

• Flat or Low-slope sections 
• South- or West-Facing Slopes 
• Near flashings and roof edges
• Around roof penetrations 
• Under ponding water areas

Read More About: Essential 37 Roof Parts: Importance and Leak Proofing

Which Types of Roof are Most Prone to Alligatoring?

Mostly alligatoring roof types are low-slope roofs. Low slope roofs have a lower pitch and it has a lower efficient at draining water on the slope. This causes to alligatoring the roofing over time. As well as the mostly alligatoring roofing is asphalt-based roofing and elastomeric coated roofing. These roofing can be damaged by exposing the water and sun light over time.