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Here are some waterproofing hints drawn from the extensive experience of Gordon Anderson, one of South Africa’s foremost authorities on waterproofing, who consults to a.b.e. Construction Chemicals.
a.b.e, part of the Chryso Southern Africa Group, has for close to 75 years been manufacturing products synonymous with waterproofing in South Africa. Anderson’s reputation in waterproofing is equally impressive. He is a former MD of Gundle Coatings, and board member of the Derbigum Group, and has decades of experience in waterproofing.
In this article, Anderson deals with preparing for the summer rains:
There are essentially four common types of roof finishes in South Africa: tiled roof, slate roof, flat roof, and “tin” roof. Here’s what to consider before the rains set in for summer:
All gutters should be cleared of debris and downpipes checked to see if they are running freely. A visual inspection of the tiles would show any cracked or broken tiles, which should be replaced. Roof valleys should be checked and cleaned to ensure free flow of the rainwater. The ridge tiles should be inspected for displacement or cracking. Tile cracks can be treated with a.b.e. Super Laykold, a rubberised liquid bitumen emulsion, which must be used in conjunction with a.b.e. membrane which can be used to waterproof flashings, parapet walls, roofing joints, laps and roof screws on corrugated roofs.
a.b.e. Super Laykold requires over-coating with a.b.e. Silvakote to protect against UV exposure to enhance the longevity of the waterproof coating; or with Super Laykold bandage material tape, a peel-and-stick bitumen waterproof tape with aluminium foil, to protect the bitumen from UV-lamination on the upper exposed side.
As most tiled roofs have parapet walls, the crowns of these walls should be examined for cracks in the plaster. Deterioration of the wall will be speedy if the correct actions are not taken: the use of either a.b.e. Super Laycryl, with a.be. membrane, or Super Laykold with a.b.e. membrane will prevent water ingress and extend the life of the plastered parapet crown.
Prior to the rains, gutters should also be cleaned and downpipes checked. Valleys should be cleared of obstructions and ridges checked for displacement. A visual examination of the slate tiles should show any cracked or broken slates and slippage or displacement.
A slate roofing contractor should inspect the integrity of the under-tile membrane to ensure that the membrane is still sound to prevent leaks.
Flat concrete roofs are often regarded as “the roofs that leak”. However, to seal a conventional screeded roof should not be difficult. Often the use of unskilled waterproofers result in problems but this is not the point of this article which is the maintenance of an installed system.
Prior to the onset of the rains, the flat roof area should be swept clean of wind-blown debris, the outlets cleared to allow free flow of rain water. The internal angles i.e. the joints between the wall and floor, are the most likely to leak so these areas should be checked regularly; as well as the lap joints of the bitumen membranes by an approved waterproofing contractor every two years to ensure the membrane laps have not opened up.
The areas between the horizontal and vertical interfaces should be checked for damage either through movement, or wear and tear, and repaired with materials compatible with the waterproofing system installed. The life cycle of a flat roof can be extended by the application of a.b.e. Silvakote which protects against UV attack and acts as a thermal barrier by reflecting the rays of the sun, thereby reducing the internal temperature.
The life cycle of a flat roof with a bitumen waterproofing membrane can be extended by coating the waterproofing every two to three years with a.b.e. Silvakote which will protect the bitumen membrane from degradation from the UV rays.
Again, gutters and downpipes should be cleaned regularly, the valleys cleaned, and the ridges inspected. The wind can cause the sheets to move against the securing fasteners, widening the penetration and allowing water ingress.
The lap joints, cross-lap joints and roofing bolts on metal roofs can be easily waterproofed with three coats of a.b.e. Super Laycryl. A recent product addition is heat-reducing a.b.e. proof Thermoshield which can reduce internal temperatures between 7 and 9 degrees Celsius.