How to paint a mabati roof in Kenya (step by step)

A mabati roof takes more punishment than any other surface on a Kenyan building: direct equatorial UV all day, heavy rain in the long rains, and expansion and contraction every single afternoon. Paint that would last a decade on a wall can fail on mabati in two seasons if the prep is wrong.

Here is how to do it properly.

1. Wash the roof first, and do it properly

Almost every peeling roof we get called about failed at this step, not at the paint.

Iron sheets collect a film of dust, soot, bird droppings and, on newer sheets, a residue of oil from the rolling mill. Paint cannot bond through any of that.

• Sweep the roof dry first to get the loose material off.
• Wash with water and a strong detergent, scrubbing with a stiff brush.
• Rinse thoroughly. Detergent left behind is as bad as the dirt.
• Let it dry completely. Give it a full sunny day.

For brand-new sheets, wipe the surface with a thinner-dampened cloth to cut the mill oil. Skip this and you will be repainting next year.

2. Deal with the rust

Rust spreads underneath paint. Covering it does not stop it.

• Wire-brush every rust patch back to bare metal. An angle grinder with a wire cup saves hours on a big roof.
• Sand the edges so there is no hard ridge between bare metal and sound paint.
• Any sheet that has rusted through should be replaced, not painted. Paint is not a patch.

3. Prime the bare metal

Bare metal must be primed the same day you expose it. It will start to flash-rust within hours in humid weather.

Use a red oxide or zinc phosphate metal primer on every bare patch. On a roof that has been stripped back extensively, prime the whole surface rather than spot-priming, so you get an even substrate for the topcoat.

Let the primer cure for the full time on the tin. Rushing this is the second most common cause of failure after poor washing.

4. Choose the right topcoat

For mabati you want a coating that is:

• Elastomeric or flexible enough to move with the sheets as they expand and contract.
• UV-stable, so the colour does not chalk out in eighteen months.
• Reflective, if you want the room below to stay cooler. A lighter roof colour makes a real difference under an uninsulated ceiling.

A standard wall emulsion is not a roof coating. It has none of these properties and will fail.

5. Work out how much you need

Coverage on mabati is lower than on a flat wall because the corrugation increases the actual surface area, so budget roughly 15–20% more paint than the flat plan area suggests.

A rough working figure:

Roof plan area	Coats	Approximate paint needed
50 m²	2	12–14 litres
100 m²	2	24–28 litres
200 m²	2	48–56 litres

Always check the spreading rate printed on the tin, since it varies by product, and buy all your paint in one batch so the colour matches across the roof.

6. Apply it correctly

• Two coats, always. One coat on mabati is a false economy.
• Paint along the corrugations, not across them, so you get into the valleys.
• Do not paint in direct midday sun on a hot roof. The coating skins over before it can wet the surface properly. Early morning or late afternoon is better.
• Do not paint if rain is likely within the drying window on the tin.
• Respect the recoat interval between coats.

7. Safety

A mabati roof is slippery, hot, and often over an unprotected drop.

• Use roof ladders or crawl boards to spread your weight. Do not walk directly on unsupported sheets.
• Wear shoes with grip, and gloves when wire-brushing.
• Do not work on a roof in wind or rain.
• If the roof is high or steep, hire someone who does it for a living.

Common mistakes

1. Painting over rust. It always comes back.
2. Skipping the primer on bare metal.
3. Using wall paint because it was cheaper.
4. One coat instead of two.
5. Painting a dirty or oily new roof.

Get the prep right and a good roof coating will hold for years. Get it wrong and no paint on the market will save the job.

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Need help specifying a roof coating for your project? Talk to us and we will work out the quantities with you and quote delivery to site anywhere in Kenya.