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Cracking (Part 1)
Description
Cracking caused by stress throughout and between the film and substrate. The underlying black bituminous coating and alkyd enamel topcoat in this example have expanded differently, causing the stress cracking in the enamel topcoat.
Possible diagnosis
- A less flexible topcoat such as enamel not compatible with a more flexible substrate like bitumen.
Remedy
- Remove cracking top coat and recoat with a compatible system such as NEO Gloss Acrylic.
Cracking (Part 2)
Description
Cracking caused by stress throughout and between the film and substrate. The underlying black bituminous coating and alkyd enamel topcoat in this example have expanded differently, causing the stress cracking in the enamel topcoat.
Possible diagnosis
- A less flexible topcoat such as enamel not compatible with a more flexible substrate like bitumen.
Remedy
- Remove cracking top coat and recoat with a compatible system such as NEO Gloss Acrylic.
Paint Flaking from Fibrecement Building Products
Description
Flaking top coat with friable, powdery fiber cement underneath.
The top coat consists of enamel paint.
Possible diagnosis
- Omission to remove dust and dirt from new or well weathered fibrecement boards.
- Omission to remove mold, moss or lichen from weathered boards.
- Omission to use an alkali-resistant water-based primer such as NEO Acrylic Wall Primer.
- Overcoating a water-based primer with an alkyd enamel.
Remedy
- Remove all loose and flaking paint.
- The surface may be damp but not wet.
- Apply a solvent-based alkali-resistant primer.
- Note: Pure acrylic emulsion paints such as NEO Dur (SABS Grade1), NEO Multi Dur (SABS Grade 2) or NEO Roof Paint are best for fiber cement building materials.