Roof Crocodiling or Alligatoring


flat roof crocodiling of waterproofing
Flat roof waterproofing looks like crocodile skin. This is crocodiling!

Waterproofed concrete and composite flat roofs on residential and commercial buildings require more maintenance than sloped roofs. They react differently to sun and moisture than tiled or sheeted roofs and require more frequent maintenance to ensure they function as they should. One common problem with many flat roofs is crocodiling.

What is Crocodiling?

Crocodiling is a crazed cracking pattern on the surface of the waterproofing. It looks like crocodile skin, which is where the name comes from.

Crocodiling is a sign that your waterproofing is ageing. The sun’s UV rays dry out and damage the waterproofed surface, and after five years or more years, the coating may develop small cracks. The older your roof gets before you repair the crocodiling, the more expensive it will get.

Extreme temperature changes, changing from hot sunshine to sudden cloudbursts and rain, and even hot winter days and very cold nighttime temperatures will cause new cracks to appear and will make existing cracks worse. 

Leaves and debris will allow water to pool on the membrane which, together with the elements, will hasten the deterioration of the protective coating and waterproofing itself.

Preventing crocodiling on the waterproofing

It is possible to prevent premature crocodiling by keeping the roof clean and repairing small patches that appear before they get so bad that you have to replace your flat roof prematurely.

Flat roofs require more upkeep than tiled or sheeted roofs. Therefore it is important to keep up regular maintenance to extend the life of the waterproofing on your roof. Regular inspections will ensure that you repair any small crocodiling problems before they become larger. Your waterproofer should apply a UV protectant or reflective coating on a consistent schedule to prevent crocodiling and other damage from happening.

Repairing the waterproofing

If you notice small splits and cracks in your waterproofing, the best way is to remove and patch the problem area. In general, it’s best to just get rid of those troublesome sections as they appear. 

When Crocoldiling has gone too far

At some point, crocodiling can become a cause for replacement. If not taken care of quickly, cracks can continue to split down through the roofing membrane where they will eventually cause it to bubble and result in water damage to the concrete roof slab, your ceiling and walls. At this point, it’s better to replace the waterproofing, rather than do several costly and extensive repairs over time.

Here are a few signs that crocodiling has advanced to the point that you should replace your waterproofing:

  • When water is seeping into your building. If you’re noticing any kind of water damage on the ceiling or at the junction of the walls and ceiling due to the cracks in your roof, it’s time for a replacement. 
  • If crocodiling has spread across the roof. Crocodiling usually starts in one or more spots, and then gradually expands as cracks widen and extend. If you’re noticing that crocodile pattern across your entire flat roof, it’s time for a replacement. 
  • When your waterproofer recommends a replacement. If your waterproofer does his routine inspection and recommends it might be time to replace your roof, don’t wait. The longer it takes you to get the waterproofing replaced, the harder (and more expensive) the job will be. 

Crocodiling is a difficult and common problem with waterproofing, but there are ways to prevent it from shortening the life of the waterproofing on your flat roof.

Speak to your waterproofer about a maintenance contract! He will be able to spot problems with the waterproofing long before you will.

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