Cleaning changes how a roof looks and prepares it for any coating, but it is surface work. It does not fix cracked tiles, failed ridge pointing, rusted sheets or a leak. A good cleaning quote is honest about that, and about the ways cleaning itself can damage a roof if the method does not suit it.
Concrete tile roofs, common across Perth’s suburbs, are the most frequent candidates, because their textured surface holds dirt, lichen and moss. Steel roofs and terracotta can be cleaned too, but usually more gently.
When is roof cleaning the right job?#
Cleaning makes sense when the covering is sound and the main issue is growth, dirt or debris. Common reasons homeowners ask about it:
- Concrete tiles darkened by dirt or patched with grey, orange or green lichen.
- Moss or debris building up in tile laps, valleys and gutters.
- A roof being prepared for roof painting or a full restoration.
- Preparing a home for sale or rental photos.
- Salt and grime on sheltered parts of a coastal steel roof.
If tiles are broken, ridges are cracked or water is coming in, cleaning alone will not help. Ask for an inspection that separates repairs from cleaning. Our guide to lichen and moss on roofs explains what the growth is and what it means for the tiles.
Pressure cleaning or chemical treatment: what is the difference?#
The two main approaches work in different ways and suit different roofs. Many jobs use a combination.
| Method | How it works | Often suits | Risks to discuss |
|---|---|---|---|
| High-pressure water | A wand or rotary surface cleaner strips growth and loose material | Sound concrete tiles before a coating | Cracked tiles, eroded tile surface, water forced under laps, stripped coatings |
| Low-pressure chemical treatment | A treatment is applied at low pressure to kill growth, sometimes rinsed off | Fragile or painted roofs, maintenance cleans | Runoff into gardens, pools and tanks; overspray; slower visible results |
| Gentle washing | Hosing, soft brushes and mild detergent | Painted steel and other coated surfaces | Limited effect on established lichen |
The right choice depends on the material, its age and what happens next. A roof about to be coated needs a thoroughly clean, sound surface, while a maintenance clean may favour the gentler options.
What can go wrong during roof cleaning?#
Most cleaning damage comes from too much pressure, the wrong technique or foot traffic on fragile tiles. Ask how the contractor will avoid:
- Cracked or broken tiles. Older concrete and terracotta tiles can crack underfoot or under a concentrated jet.
- Eroding the tile surface. High pressure on weathered concrete tiles can remove more of the surface than intended.
- Forcing water under the tiles. Spraying up the slope drives water under laps, past flashings and into the roof space, where it can stain ceilings.
- Stripping coatings. Pressure can lift an existing roof paint that is still sound, or remove loose pointing from ridges.
- Blocking gutters. Lichen, grit and paint flakes wash into gutters and downpipes.
An inspection before cleaning should record existing damage with photos, so it is clear what was there before work started.
How are runoff, gardens and neighbours protected?#
Cleaning water and any chemical treatment have to go somewhere. Ask for the product name and its safety information, and how the contractor will:
- Cover or rinse plants and garden beds near downpipes and eaves.
- Protect pools, ponds, fish and pets.
- Disconnect or divert downpipes that feed a rainwater tank.
- Keep runoff out of stormwater drains and off neighbouring properties.
- Manage overspray onto walls, windows, paving, cars and the house next door.
It is courteous to tell neighbours when the work is booked, so they can close windows and move cars.
How are metal roofs cleaned?#
Painted steel roofs, including pre-painted steel such as COLORBOND steel, are usually washed gently rather than blasted. LYSAGHT’s maintenance guidance for its roofing describes sweeping debris with a soft brush or leaf blower, avoiding shovels and hard tools, and hosing down the roof and gutters. It notes that coating breakdown generally results from poor maintenance techniques and scratching. On coastal homes, areas that rain does not wash, such as under overlaps and sheltered sections, collect salt; see coastal roofs and salt corrosion.
Cleaning will not fix rust. If spots of corrosion appear once the roof is clean, see metal roof repairs.
What about solar panels?#
Solar panels need their own care. Ask the contractor whether they will clean the panels, how they will keep water and chemicals off panel connections and wiring, and whether they follow the panel maker’s cleaning instructions. Tiles under the panels usually cannot be cleaned unless the panels are lifted, which is a job for a licensed electrician or solar installer. Our guide to roof work and solar panels covers the coordination.
Is cleaning a restoration step or a job on its own?#
Both. As stand-alone maintenance, cleaning improves appearance and clears debris from valleys and gutters. As part of a roof restoration, it prepares the surface for repairs and coating, and the roof must be fully dry before any coating goes on. Cleaning can reveal cracks and loose pointing that lichen was hiding, so ask how any defects found will be reported and priced before extra work goes ahead.
Why must asbestos cement roofs never be pressure cleaned?#
High-pressure water cleaning of asbestos cement roofs is prohibited in WA. It breaks down the sheet surface and spreads asbestos-contaminated residue across the property and onto neighbouring properties. Contaminated residue must be cleaned up by a licensed asbestos removalist, and clean-ups can be very expensive. If your home was built before about 1990 and has a grey corrugated cement roof, treat it as asbestos until tested and read about asbestos roof replacement.
What should a roof cleaning quote clarify?#
- Method and pressure. High pressure, low pressure, chemical treatment or a combination.
- Products. The name of any treatment and whether it suits the roof material.
- Protection. How gardens, pools, tanks, paving and neighbours will be protected.
- Breakages. How many replacement tiles are allowed for and whether spares are matched.
- Gutters. Whether gutters and downpipes are cleared after cleaning.
- Defects. How problems found during cleaning will be reported and approved.
What is usually included, and what is not?#
| Usually included | Often extra or excluded | Worth asking about |
|---|---|---|
| Cleaning the roof surface | Repairs to tiles, ridges or valleys | How existing damage will be recorded |
| Clearing debris from valleys | Cleaning solar panels | Who lifts panels if tiles beneath need work |
| Flushing gutters after cleaning | Gutter guard removal and refitting | Whether downpipes are flushed too |
| Basic masking and site clean-up | A follow-up chemical treatment | Whether a treatment is applied at the end |
What affects the price of roof cleaning in Perth?#
The main factors are the roof area and pitch, the material and its condition, how heavy the growth is, the method and products, height and access, and features such as valleys, solar panels and multiple levels. Protecting a pool, garden or tight boundary adds time. If cleaning is part of a restoration, it is usually priced within that scope.
Questions to ask the contractor#
- What method and pressure will you use on my tiles or steel, and why?
- What product will you apply, and is it safe near my garden, pool or tank?
- Who will walk on the roof, and what fall protection will be used?
- How will you avoid forcing water under the tiles?
- Will you clean the gutters and downpipes at the end?
- What happens if you crack tiles or find damage?
Frequently asked questions
Can roof cleaning damage my tiles?
It can, through foot traffic on fragile tiles or pressure that is too high for their condition. Ask the contractor how they will walk on the roof, what pressure they will use and how breakages will be replaced.
Is a chemical lichen treatment safe for my garden and pool?
That depends on the product and how it is applied. Ask for the product name and safety information, and how plants, pools, tanks and pets will be protected from runoff and overspray.
Do I need to clean my roof before it is painted?
Yes. Coatings need a clean, sound, dry surface to bond, so cleaning is normally the first stage of a painting or restoration job and should be included in that quote.
Can a metal roof be pressure cleaned?
Painted steel is usually washed gently with a hose and soft brush rather than high pressure, which can damage the finish and force water under laps. Ask the contractor to follow the roofing manufacturer’s maintenance guidance.
Will cleaning stop lichen from coming back?
Not permanently. Lichen and moss can regrow over time, especially on shaded or damp parts of the roof. Ask the contractor what treatment, if any, they apply to slow regrowth and what they suggest for ongoing maintenance.