Roof Crocodiling or Alligatoring

WHAT IS ROOF CROCODILING AND HOW DOES IT AFFECT YOUR FLAT ROOF?

flat roof crocodiling of waterproofing
Flat roof waterproofing looking 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 in 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 protective coating and waterproofing itself.

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Leaks at Window Sills

Moisture Intrusion at Window Sills

window sills

During many property inspections, I keep coming across moisture problems associated with water leaking into window sills and at windows.

Moisture absorbed into brickwork and plasterwork causes them to expand slightly. When the brickwork and plasterwork dry they contract slightly. The water absorbed by the bricks and plasterwork usually causes a slight vertical crack at the edges of the internal window sills. The paint then starts to bubble along the vertical crack. This crack may continue around the length of the window sill before you notice it. What started out as a small vertical crack then becomes a horizontal crack along the bottom of the window sill on the interior face of the sill wall.

The cracks are usually not significant unless allowed to continue unabated.

Rising Damp

Sometimes the moisture intrusion at sills are mistaken for rising damp! Water leaking in at the window sill may bypass the damp proof course (DPC) built in under the window sill as a water-resistant barrier. The moisture may then appear as bubbling paint or crazing cracking of plasterwork, or both, below the window, extending down to floor level.

On external face-brick walls, this may appear as efflorescence (a white powder).

Internally, this may appear as bubbling paint above the skirting or discolouration of the skirting itself.

How do you prevent the moisture intrusion into window sills?

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