The Difference Between New and Weathered Mabati#
Corrugated iron roofing sheets (mabati) protect millions of homes, warehouses, churches, and schools across Kenya. Yet painting mabati is frequently misunderstood.
The first critical rule: Never paint brand-new galvanized mabati straight out of the hardware store with standard roof paint. New galvanized steel is coated at the factory with oil or chromate passivating solutions to prevent white rust during transit. Paint applied over this factory film cannot bond and will peel away in large sheets.
There are two options for new mabati: either allow it to weather naturally in the rain and sun for 6 to 12 months until the zinc surface becomes slightly rough and dull, or chemically degrease the sheets and apply a specialized etch primer (wash primer).
Restoring Old, Rusted Corrugated Roofs#
For older roofs that have already turned brown with rust, painting is an excellent, cost-effective alternative to expensive sheet replacement, provided it is done before structural holes develop.
The restoration protocol requires:
1. Stiff Scrubbing. Scrub the entire roof using water, detergent, and wire brushes to remove airborne dust, soot, moss, and loose rust scale. Rinse thoroughly with clean water.
2. Rust Treatment and Priming. Coat all exposed red rust areas with a dedicated zinc phosphate metal primer or rust converter. This arrests corrosion and provides a stable bonding layer.
3. Sealing Screw Fasteners. Roof leaks almost always start around fixing screws where rubber EPDM washers have hardened and cracked under UV exposure. Replace degraded screws and apply acrylic roofing sealant over screw heads.
4. Application of Acrylic Roof Paint. Apply two liberal coats of high-grade roof paint (such as Solai Roof Paint, Crown Roof Paint, or Duracoat Roofguard). Ensure the first coat has dried completely (minimum 4 hours) before applying the second.
Thermal Comfort: Why Roof Colour Changes Indoor Temperatures#
In Kenya, uninsulated mabati homes can become stifling hot ovens by 2:00 PM, radiating oppressive infrared heat downward into living rooms and bedrooms.
Dark roof colours (such as dark brown, charcoal, or dark blue) absorb over 85% of solar radiation, heating metal sheets up to 70 degrees Celsius. By contrast, specialized solar-reflective roof paints in white, pearl, light terracotta, or sky blue reflect up to 75% of solar rays.
This simple colour shift lowers the sheet temperature by up to 20 degrees Celsius, translating into a noticeable 3 to 6 degree drop in room temperature beneath uninsulated ceilings.