For the house itself (roof, render, weatherboard, painted brick, Hebel), soft washing wins every time. Low pressure and a biocide solution kill mould and lichen at the root, so results last 3 to 5 years instead of months. Pressure washing belongs on concrete, pavers and paths. Most northside homes need both, on the right surfaces.
Soft wash the house. Pressure wash the driveway. That is the answer to the soft wash vs pressure wash house question, and for most homes on Brisbane’s northside it is the whole answer. Roofs, render, weatherboard, painted brick and Hebel belong to soft washing: low pressure, a solution that kills the growth, then a proper rinse. Concrete, pavers and paths belong to pressure washing, because there is nothing on a slab to strip.
The reason comes down to what the black streaks are. Mould, algae and lichen are living organisms rooted into the surface. Blast the top off at 3,000 psi and the roots stay. The spores spread, and the wall looks grubby again within a year. Kill them at low pressure, and it stays clean for years.
What is soft washing vs pressure washing?
Soft washing cleans with chemistry rather than force. Water pressure stays under 500 psi, low enough that it will not lift paint, and a biocide solution (usually sodium hypochlorite-based, with a surfactant so it clings to vertical surfaces) is applied, left to dwell, then rinsed off. Pressure washing runs from about 1,500 psi on a hired unit to 4,000 psi on a commercial rig and relies on mechanical force alone.
So if you are asking what is soft washing vs pressure washing, the honest answer is that they remove different things. Loose grime comes off with force. Mould and lichen only stay off once they are dead.
How each one works on the day
Plants get pre-wet and sensitive ones covered. The solution goes on at low pressure, mixed to suit the surface: a tile roof with established lichen gets a stronger mix than painted weatherboard. It sits for 10 to 20 minutes, then everything gets rinsed down, windows, paths and garden beds included. The active is the same as in pool chlorine, so the skill is in dilution, dwell time and rinsing. Pressure washing is a pump, a nozzle and impact. On a driveway, the wand is swapped for a surface cleaner, a rotating head under a hood that leaves an even finish instead of tiger stripes.
Which method wins on each surface
Roofs (concrete tile, terracotta, Colorbond): soft wash only
No exceptions. Concrete tiles carry a thin coloured surface layer that high pressure strips off, leaving the tile pale, porous and quicker to grow lichen than before. Terracotta glaze chips. Colorbond paint scours and dulls. Monier, one of Australia’s largest roof tile makers, says plainly on its own maintenance page that it strongly advises against pressure washers for roof cleaning. Tim’s roof cleans are soft wash only, gutter flush included.
Render, weatherboard, Hebel and painted brick: soft wash
Render is porous and etches under a high-pressure wand, leaving pale arcs that only a repaint fixes. Weatherboard and fibre cement have laps and joins, and pressure pushes water straight through them into the wall cavity. Hebel crumbles at the edges. Painted brick loses paint. All of them come up clean with a soft wash, so that is the method for the whole house exterior, eaves, fascias and garage doors included.
Driveways, concrete paths and pavers: pressure wash
This is where pressure earns its keep. Concrete takes 3,000 psi without complaint, and a surface cleaner with a mould or oil pre-treatment leaves an even finish. Pavers need a lighter touch, since too much pressure blows the sand out of the joints. Exposed aggregate and pool surrounds get the same: calibrated pressure, pre-treated where growth is heavy.
Decks, timber and fences: low pressure, case by case
Timber decking furs up much above 1,000 psi, so decks get a low setting and a wide fan nozzle, often after a soft wash solution has done the killing. Colorbond fences are soft washed like a wall. Timber fences depend on age and coating, and a look on the day decides it.
What does pressure washing a house actually damage?
Pressure washing a house forces water behind cladding, strips paint, etches render, scours the surface off roof tiles and scatters live mould spores across the property. Most of the damage is not visible on the day. It shows up months later as bubbling paint, damp inside a wall, or a roof that has gone green again by autumn.
- Water behind cladding. Weatherboard laps and window flashings shed rain falling downward, not a jet aimed sideways at 3,000 psi. Water in the cavity takes weeks to dry and lifts paint from behind.
- Stripped paint and etched render. Older acrylic goes patchy and the wand leaves permanent lighter arcs in render. Both mean a repaint.
- Spread growth. Blasting lichen scatters fragments and spores across the rest of the roof, which is why a pressure-washed roof often comes back worse.
Then there is the warranty question. If a steel or coating claim ever comes up, the manufacturer’s care guidance is what your maintenance gets measured against. BlueScope’s Technical Bulletin TB-4 for Colorbond describes mild soap, a sponge or soft nylon brush and a fresh water rinse, with unwashed areas hosed down at least every six months and every three months near salt spray. A 3,000 psi lance appears nowhere in it. Read that bulletin and Monier’s page and the soft wash vs. pressure wash argument for roofs is over.
Why soft wash results last longer
Because the growth is dead, not trimmed. A soft wash solution soaks into mould, algae, lichen and moss and kills the organism, spores included. On the north-side roofs, Tim soft washes. The result holds for 3 to 5 years, and house exteriors often go longer. Pressure-washed roofs, in his experience, look dirty again within 6 to 12 months. Lop the top off a living thing and leave the root, and that is what you get.
What about cost and time?
A pressure wash is often quoted cheaper because running a high-pressure wand over a house is quick. The catch is that high pressure is the wrong method for most home exteriors, so that lower price can come with stripped paint, damaged render and water forced behind cladding. A soft wash takes longer on site, mostly because the cleaning solution needs time to dwell before a thorough rinse. The payoff is that it treats mould and algae at the root rather than just blasting off what you can see, so your home typically stays clean for years rather than months. To keep things simple, our quotes are fixed, based on photos you send us, and back to you within 24 hours.
How the right method changes across Brisbane’s northside
The soft wash vs pressure wash house verdict does not change from suburb to suburb. What does change is the mix strength, how often the clean is due, and where Tim looks first.
Chermside, Stafford, Kedron, Wavell Heights, Aspley and Bridgeman Downs
Older, leafier streets with more shade and more moisture sitting on roofs and southern walls. Lichen is well established and render mould is heavy, so these roofs need a stronger mix and a longer dwell. They are also the ones most likely to have been pressure washed by a previous owner, pale patches and all.
North Lakes, Mango Hill, Griffin, Murrumba Downs, Kallangur and Burpengary
Newer builds, mostly Colorbond roofs and rendered or Hebel walls, and a fair share on tank water. Growth is lighter, so a heavy first clean matters less than getting onto a schedule before the streaks set in: every 12 to 18 months on the house, every 2 to 3 years on the roof. Tank inlets get disconnected before the roof is treated, every time.
Sandgate, Brighton, Bracken Ridge, Shorncliffe and Deagon
Salt air changes the job. BlueScope’s bulletin notes that dust and salt building up in sheltered spots can start corrosion on coated steel, which is why it calls for more frequent washing near the coast. Bayside homes get a closer look at fascias, roof screws and the underside of eaves, where salt collects and rain never reaches. Surface rust gets flagged in the walkthrough.
Is soft washing safe for tank water and gardens?
Yes, with three habits that are not optional: disconnect the tank inlet before any roof treatment, pre-wet and cover plants, and rinse everything afterwards. Queensland Health’s rainwater factsheet is blunt that chemicals can enter a tank from the roof and that boiling does not remove them, so the downpipe stays off through the clean, the rinse and the first decent rain. The federal enHealth guidance adds that bitumen-coated roofs, exposed treated timber and uncoated lead flashing should not feed a drinking tank at all.
Gardens are simpler. The solution is biodegradable, plants are pre-wetted so they do not take up runoff, sensitive ones are covered, and every surrounding surface is rinsed at the end. Diluted sodium hypochlorite breaks down quickly in sunlight, which is why dilution and a proper rinse matter more than the product. Keep pets off cleaned areas for about an hour after the rinse.
Frequently Asked Questions
Can I pressure wash a Colorbond roof?
No. High pressure scours the paint, dulls the finish and scatters lichen spores across the sheets. BlueScope’s care bulletin for Colorbond describes gentle washing with a soft brush or sponge, mild soap and a fresh water rinse. A soft wash does that job with a low-pressure biocide solution, kills the growth at the root, and holds for 3 to 5 years.
How often should a northside house be soft washed?
Every 12 to 18 months for the house exterior and every 2 to 3 years for the roof suits most North Brisbane homes. Push toward the shorter end under heavy trees in Kedron or Aspley, or in salt air around Sandgate and Brighton. Newer estates like North Lakes can usually stretch a little further, as long as they start before the streaks set in.
Can I do it myself with a hired pressure washer?
On a concrete driveway or path, yes, with a wide fan nozzle and patience. On the house or roof, no. A hired unit runs 1,500 to 3,000 psi, enough to strip paint, etch render and push water behind weatherboard, and it will not kill the growth, so the mould is back within months. Soft washing needs a dedicated low-pressure pump and chemistry mixed for the surface.
Not sure which method your place needs?
Send a couple of photos and Contact Tim on 0477 913 333. North Brisbane Pressure Washing will send you a fixed quote within 24 hours.
About the Author
The North Brisbane Pressure Washing Team, Soft wash specialists, Brisbane Northside
North Brisbane Pressure Washing is an owner-operated exterior cleaning business serving Brisbane’s northside, from Chermside to North Lakes, Albany Creek and the bayside suburbs. The team specialises in soft washing roofs, houses and driveways, matching the method to the surface so growth is killed at the root without damage. Fully insured, 5-star rated, and local. You deal directly with Tim, the person who quotes the job.
