How to clean Colorbond roofing, fences & cladding

Colorbond is on a huge share of Canberra roofs, fences, sheds, garage doors and cladding — and it's a surface people routinely damage by treating it like concrete. The paint system is durable but thin, and the sheeting itself is light. Everything about cleaning it comes down to being gentle and being thorough about rinsing.

What actually builds up on Colorbond

• Mould and algae — green-black film, worst on shaded south-facing panels and anywhere a garden bed or shrub touches the sheet.
• Chalking — a fine powdery layer of degraded binder from years of UV exposure. Rub the surface and it comes off on your hand. Washing removes the loose chalk; it doesn't undo the UV wear.
• Dirt in sheltered zones — under eaves, verandah soffits and the top of fence panels, where rain never rinses the surface.
• Lichen — crusty patches on roof sheeting, usually where a tree overhangs.
• Rust bleed at cut edges and fixings — small orange runs at screws, cut ends and drilled holes. That's damage, not dirt.

The rules for Colorbond

Do	Don't
Mild detergent in warm water	Abrasive cleaners, scouring pads or steel wool
Soft-bristled brush, sponge or microfibre	Harsh solvents, turps or thinners
Low-pressure rinse, top-down	High-pressure blasting or turbo nozzles
Rinse thoroughly with clean water	Letting cleaner dry on the surface
Work in shade or on a mild day	Washing hot sheeting in full summer sun
Check the manufacturer's care guide	Assuming anything that works on concrete is fine here

Cleaning a Colorbond fence

1. Cut back anything touching the panels. Shrubs and creepers hold moisture against the sheet and are the number one reason one side of a fence looks worse than the other.
2. Rinse off loose dirt with a hose at normal pressure.
3. Wash bottom-up with warm water and mild detergent, using a soft brush. Working upward stops dirty runs streaking down dry sections.
4. For mould, apply a diluted mould-killing solution, let it dwell about ten minutes without drying, then agitate gently.
5. Rinse top-down thoroughly with clean water — both faces of the fence if you can reach, plus the ground and plants below.
6. Check the base rail and posts for rust bleed while you're there. Early treatment is much cheaper than replacing panels.

Cleaning a Colorbond roof

Same chemistry, much higher stakes. Metal roof sheeting is slippery when wet, roof screws and flashings are easy to disturb, and a fall from a roof is a serious injury. If you're going up regardless:

• Never blast it. Pressure dents thin sheeting, forces water up under laps and flashings into the roof space, and abrades the coating.
• Work top-down and away from you, and never walk on wet, treated sheeting.
• Clear the gutters first so the debris and residue you wash down has somewhere to go — see our gutter cleaning guide.
• Avoid mixing metals. Runoff from copper or lead onto Colorbond can cause staining and corrosion.
• Rinse comprehensively. Any cleaner left on the sheeting will mark it as it dries.

For tile roofs the considerations differ again — that's covered in roof moss, lichen and black stains.

Why Canberra is tough on Colorbond

The ACT climate does two things to metal at once. Summer delivers high UV that accelerates chalking on north and west faces, while winter delivers long damp shade and heavy frost that keep the south side wet enough to grow mould for months. The practical upshot is that opposite sides of the same fence or roof often need different attention: the sunny side is fading, the shaded side is going green.

How often to wash it

Area	Frequency
Sheltered areas never rinsed by rain (under eaves, soffits, verandahs)	Around every 6 months
Fence panels, particularly the shaded side	Every 6–12 months
Exposed roof sheeting and walls	Every 12 months
Garage doors and sheds	Every 12 months

Regular gentle washing is what keeps a Colorbond finish looking good for its full service life. It also stops the situation where the only way to make a fence presentable is repainting it.

When to get someone in

Roof work, two-storey cladding, long runs of fencing, and anything with established lichen or heavy chalking are all better handled with proper soft-wash equipment and height safety. A Canberra roof clean and treatment typically runs $399–$900, and a house exterior soft-wash — which covers Colorbond cladding, garage doors and sheds — $250–$600. Full ranges are in the cost guide.

FAQs

Can you pressure wash Colorbond?

You can rinse it at low pressure, but Colorbond should not be blasted. High pressure can dent thin sheeting, drive water up under the laps and flashings, and abrade the paint finish. The correct approach is a soft wash — a mild detergent solution, a soft brush, and a gentle rinse.

What is the best thing to clean a Colorbond fence with?

Warm water with a mild household detergent and a soft-bristled brush or sponge handles most grime. For mould, a diluted cleaning solution left to dwell before rinsing works well. Rinse thoroughly with clean water afterwards — detergent left on the surface can mark the finish.

Will bleach damage Colorbond?

Strong or undiluted chlorine bleach left sitting on Colorbond can attack the coating and any exposed cut edges or fixings. If you use a chlorine-based product for mould, keep it well diluted, don't let it dry on the surface, and rinse the whole panel thoroughly — including the ground below and any adjacent metalwork.

How do I remove mould from a Colorbond fence?

Wet the panel, apply a diluted mould-killing solution, let it dwell about ten minutes without drying out, agitate gently with a soft brush, then rinse thoroughly from the top down. Mould on a fence almost always returns fastest on the shaded south side and wherever a garden bed sits hard against the panel.

How often should Colorbond be washed?

Manufacturers generally recommend washing any area not regularly rinsed by rain — under eaves, verandah soffits, sheltered wall sections and fence panels behind planting — around every six months. Areas that get properly rained on typically need it every 12 months or so.

Does cleaning Colorbond the wrong way void the warranty?

It can. Abrasive cleaners, harsh solvents, scouring pads and excessive pressure are all commonly excluded in coating warranties, and using them can leave you without cover for a finish failure. Check the manufacturer's care instructions before using anything stronger than mild detergent.