Soft wash roof cleaning and pressure cleaning both promise to strip years of mould, lichen and grime off your roof, and from the street the results can look almost identical on the day. Underneath, they’re very different jobs. One kills growth at the root with a treatment solution and rinses it away gently, while the other relies on sheer water force to blast it off. The method a cleaner uses decides how long the result lasts, whether your tiles or Colorbond come through unharmed, and whether you end up paying for repairs after the clean.
We clean tile, terracotta and Colorbond roofs across Brisbane, the Gold Coast and the Sunshine Coast, and we lead with soft wash on almost every residential roof. This guide explains how each method works, what high pressure can do to different roof types, where pressure cleaning still has a place, and the questions to ask before you book so you know which method you’re actually paying for.
Table of Contents:
How pressure cleaning works
Pressure cleaning, sometimes called high-pressure roof cleaning or pressure washing, uses a petrol or electric pump to fire water at the roof at high force. The dirt, moss, lichen and algae are physically knocked off the surface by the impact of the water. It’s quick, it needs little more than a machine and a hose, and the before-and-after photos can be dramatic, which is why it’s still common and why many of the cheapest quotes are based on it.
The trouble is that a roof isn’t built to be hit that hard. The same force that removes growth also works on the surface coating of concrete tiles, the glaze and edges of terracotta, the mortar pointing that holds ridge caps in place and the factory finish on metal roofing. And because the growth is torn away rather than killed, the roots and spores left in the porous surface start regrowing almost straight away.
How soft wash roof cleaning works
Soft wash works the other way around. Instead of relying on force, it applies a specially formulated treatment solution to the roof at low pressure. The solution is left to dwell, soaking into the growth and killing mould, lichen and algae right down to the roots embedded in the tile surface. The roof is then rinsed at low pressure, working from the ridge down so dirty water runs off rather than back over cleaned sections.
Because the growth is killed rather than just removed, soft wash roof cleaning keeps working after the team has left. Stubborn lichen patches often continue to fade over the following weeks as the dead growth weathers off in the sun and rain, and regrowth is far slower than after a pressure clean. You can see how this fits into our full service on our roof cleaning page for Brisbane, the Gold Coast and the Sunshine Coast.
What high pressure does to concrete tiles
Concrete tiles are the most common roof in South-East Queensland, and they’re the roof most at risk from pressure cleaning. A concrete tile is protected by a surface coating, and once that coating has weathered for a decade or two, high pressure strips what’s left of it, exposing the porous concrete beneath. That leaves a rough, absorbent surface that soaks up water and gives the next round of mould and algae an even easier foothold, so a pressure-cleaned roof can look worse within a couple of years than it did before.
Pressure also finds the weak points. Older tiles can crack under the force, and water fired up the roof can be driven under the tile overlaps and into the roof cavity, soaking sarking and insulation. If you’ve noticed cracked tiles after a past clean, our explanation of why tile roofs crack covers the common causes and what the repair involves.
What it does to terracotta and ridge capping
Terracotta tiles are harder than concrete, but older terracotta can be brittle, and its glazed or natural finish can be scarred by a pressure lance held too close. The bigger risk on both terracotta and concrete roofs is the ridge capping. The mortar pointing that bonds ridge caps to the roof is often the most weathered part of an older roof, and high pressure can wash it out in seconds, leaving caps loose and gaps open to the next storm.
When that happens, the clean has created a repair job. Our roof repointing service restores failed pointing so ridge caps sit securely again, and our guide to what roof repointing involves explains how to spot it. Soft wash avoids the problem entirely, because nothing on the roof is being hit hard enough to dislodge it.
What it does to Colorbond and metal roofs
Colorbond and other pre-painted steel roofs carry a factory-applied coating designed to last for decades. High-pressure cleaning can scratch, lift or strip that finish, particularly on older roofs where it has already weathered, and once the coating is damaged the steel beneath is more exposed to corrosion. Pressure cleaning can also void the manufacturer’s warranty, which is a costly side effect of a clean that was supposed to protect the roof.
A manufacturer-approved soft wash method cleans metal roofs safely and restores their colour without harming the finish. If your metal roof has already lost its coating and faded beyond what a clean can fix, our guide to Colorbond roof painting explains when recoating makes sense and when it doesn’t. For routine care, Colorbond’s own maintenance guidance recommends washing with clean, fresh water, which is a world away from a high-pressure blast.
Why soft wash results last longer
The difference in longevity comes down to the roots. Mould, lichen and algae grow into the microscopic pores of a roof surface, particularly on concrete tiles. A pressure clean removes what’s visible but leaves those roots and spores in place, and in Queensland’s warm, humid climate they regrow quickly. Soft wash roof cleaning kills the growth throughout, so the roof stays clean far longer.
That makes soft wash the more economical choice over the life of a roof, even though it can cost a little more on the day because of the treatment and dwell time involved. Fewer cleans over the years, no repair bills caused by the clean itself, and a surface that stays intact all add up. We explain how growth behaves in more detail in our guides to getting rid of lichen on your roof and removing algae from your roof.
Signs a roof has been pressure cleaned before
If you’ve bought a home or your roof was cleaned years ago by someone else, there are a few tell-tale signs that high pressure was used. Concrete tiles that look rough, sandy or patchy, with the colour worn away in streaks, have usually had their coating blasted off. Ridge caps with crumbling, gappy or missing pointing are another common sign, as are cracked tiles scattered across the roof rather than in one spot. On metal roofs, look for areas where the colour looks scuffed, uneven or noticeably duller than the rest.
None of these mean the roof can’t be cleaned again, but they do change the approach. A roof that’s already lost its coating needs a gentle soft wash to avoid further damage, and it may also be a candidate for repainting to restore its protection. Any loose ridge caps or cracked tiles are worth fixing before the next storm season, and our roof repair team can handle them in the same visit as an inspection.
How often a soft-washed roof needs cleaning
Because soft wash roof cleaning kills growth at the root, the gap between cleans is longer than after a pressure clean. For most South-East Queensland homes, a professional clean every three to five years keeps the roof in good condition. Homes under trees, in shaded positions or close to the coast may need it closer to every three years, while open, sunny roofs can often go longer.
Between cleans, a few simple habits stretch the result further. Trimming back overhanging branches lets the sun dry the roof after rain, keeping gutters and valleys clear stops organic debris building up and holding moisture, and dealing with small patches of growth early stops them spreading. Each later clean is usually quicker and cheaper than the first, because the roof never returns to its original state.
Is soft wash safe for gardens and pets?
It’s a fair question, since soft wash relies on a treatment solution rather than water alone. A professional soft wash is planned with the surroundings in mind. Garden beds and lawns close to the house are wetted down before and after treatment, sensitive plants can be covered, pets are kept clear of the work area, and runoff is managed and rinsed. On properties with rainwater tanks, the downpipes feeding the tank are disconnected or diverted during the clean so nothing reaches the drinking supply.
These precautions are part of what separates a careful cleaner from a quick one. When you’re comparing quotes, ask what solution will be used, how the garden will be protected and how tank water will be handled. A professional will have clear answers.
When pressure cleaning still has a place
Pressure cleaning isn’t wrong for every surface. Concrete driveways, paths, pavers and some hard, durable surfaces handle high pressure well, and there are occasional roofs with heavy build-up on a sound, robust surface where careful pressure work alongside soft wash gives the best result. The key is that the method should be chosen for the surface, not for speed.
On the vast majority of residential roofs in South-East Queensland, that choice points to soft wash. Where we do recommend a different approach for part of a job, we’ll explain why during the inspection and put it in the quote, so there’s no surprise about what will be used on your roof.
Soft wash before painting
If your roof is heading for a repaint, cleaning is the first stage of the job, and the method still matters. A roof needs to be thoroughly clean and free of growth for new coatings to bond properly, and killing growth at the root before painting reduces the risk of it pushing back through the new finish. We explain how the two stages fit together in our guide to roof cleaning and painting, and the roof painting service covers the full process.
Questions to ask before you book
Because most of a roof clean happens out of sight, it pays to ask every company the same questions before you book. Will they use soft wash or high pressure, and at what pressure? What treatment solution, and is it suitable for your roof type? Is the quote based on an on-site measure? How will they protect your garden and tank water? Are they insured and licensed to work at height? And what happens if they find existing damage?
A cleaner who answers all of these clearly and puts the method in writing is one you can trust with your roof. If the answers are vague, or the quote is far below everyone else’s, it’s worth asking whether the price reflects a pressure-only clean that could cost more later. Our roof cleaning and maintenance checklist also covers what you can do between professional cleans.
Book a soft wash clean with Apex Roof Painting
At Apex Roof Painting we’re family-owned and have been cleaning roofs across South-East Queensland for more than 10 years. We use soft wash roof cleaning on tile, terracotta and Colorbond, every clean comes with a written guarantee on workmanship and results, we carry $20M public liability cover, and we’re licensed for heights up to 20 metres. Our 50+ five-star Google reviews come from homeowners who wanted the job done properly the first time.
Whether you’re in Brisbane, Ipswich, Logan, Moreton Bay, the Gold Coast or the Sunshine Coast, we’ll measure and inspect your roof for free and give you a fixed price with no hidden costs, usually within 24 hours. You can request your free quote and mention this guide to receive 10% off.
The right method protects your roof as well as cleaning it, and on almost every Queensland home that method is soft wash.