There is a distinction to be made between the force of water and a gentle chemical application when it comes to cleaning an Australian roof. While pressure washing has its place on certain sound surfaces, it is not some panacea. One would be well advised to start with soft washing as the safer option in most cases; it will deal with lichen, moss, mould and algae without putting tiles, seals or coatings under duress. The internet may have you think otherwise but a roof is not a driveway.
I am Simon Redcliffe. I live in Melbourne in a weatherboard cottage that is not entirely straight and share my home with Arthur, a rescue greyhound. If there is one thing I have put down to experience it is that maintenance work has a way of being more than you bargained for. In the matter of roof cleaning I have come to see it as a means of averting water ingress and blocked gutters rather than an exercise in making the tiles appear new. Material, age, pitch and how much exposure the roof has to our climate are what dictate the right approach.
Choosing The Right Roof Method
With soft washing a biodegradable solution is put to work at low pressure to address organic growth before being rinsed off. A pressure washer will deploy a concentrated jet to make short work of surface staining and dirt. They are both effective roof treatment methods, yet an ill-considered mix of chemicals or too much pressure can see a routine job end up as a repair bill.
For painted surfaces and older tile work, soft washing is typically the way to go. Then again, a licensed roof cleaner who knows how to manage his spray and pressure can use a pressure washer on some metal roofs or hardy concrete tiles.
What You Get From Each
The object of a soft wash is to do away with the growth that is causing the stain. The cleaner puts on a diluted treatment and lets it have its effect before a low-pressure rinse. You may find some of the discolouration continues to fade in the days after.
Pressure washing is more of a mechanical business. The jet will strip the dirt and some of the staining right off, giving a striking contrast. Careless use, however, and it can dislodge a tile, take out the pointing or push water under the laps.
How Soft Washing Protects Roofs
Services in Australia will generally employ a biodegradable agent of some kind along with low pressure. Be it sodium hypochlorite or another biocide, the selection is down to the cleaner’s process and the roof material. It is about control, not just having the strongest chemicals on hand. A good operator will make sure the product does not run into your garden or onto outdoor furniture and will observe the instructions. Plants are not keen on an unannounced chemistry lesson.
Where Soft Washing Is Best
If you have mould or lichen on your terracotta or concrete tiles, soft washing is often the answer. Some Colorbond and other metal can be treated this way if the operator is mindful of the coating and uses something compatible, and does not let chemicals dry on sensitive areas.
It is especially handy for large tracts of organic growth since you are treating the root of it for more enduring results. That said, do not expect soft washing to put right a broken ridge cap, rust hole or any deterioration in the bedding.
Pressure Washing And Build-Up
A pressure washer will clear the accumulated grime and growth from a roof quickly and with some visual satisfaction. But it is all too easy to overdo it if the operator is in the habit of treating a roof as he would a concrete path.
You can end up with old paint stripped, asphalt shingles damaged or water driven into the cavity. Not to mention the granules being taken from the tiles. A roof that looks clean is of little value if you start to see brown freckles on the ceiling for no apparent reason.
When To Use Pressure
On a roof that is in good order and relatively new, where the manufacturer has no objection, pressure washing is fine. Or to get at heavy loose dirt prior to another form of treatment. The setting should be commensurate with the material, not because the machine has the power to do more.
Take Colorbond for instance: around the fasteners, penetrations and flashings the pressure needs to be kept in check. With concrete tiles a competent cleaner will first look for any cracks or brittleness. Aggressive pressure is not to be put on terracotta tiles, it will only mar the surface or do harm to an old finish.
Safety And Results: A Comparison
The distinction between the two is straightforward. Pressure washing is all about force; soft washing is predicated on treatment. How that plays out has implications for safety and longevity as well as for runoff, the look of the roof and the chances of inflicting some concealed damage.
Do not assume a job is safe just because there is a professional with the hose. Getting on a roof is hazardous enough, and a wet one is slippery in no time. Work health and safety must be observed at every turn, be it in the handling of chemicals, the setting up of exclusion zones on the ground or the positioning of ladders and harnesses.
| Factor | Soft Washing | Pressure Washing |
|---|---|---|
| Cleaning action | Low-pressure rinse after chemical treatment | Surface material is taken off by way of high or controlled water pressure |
| Organic growth | Mould, lichen, moss and algae are more readily treated | Visible growth can be put an end to but the underlying cause may not be |
| Risk to aged tiles | Lower provided you control the chemicals and runoff | Where tiles are cracked, brittle or not well sealed the risk is higher |
| Speed of visual result | An improvement will come in its own time post-treatment | For the most part it is right away |
| Main concern | Plant protection, runoff and overspray from the chemicals | Displaced tiles, water ingress and damage to the surface |
| Typical use | Delicate or older surfaces with organic staining | Robust surfaces where such a process is in order |
What The Roof Material Dictates
You cannot go by what the machine says. A given method might be fine for one roof and ruin another, so any competent cleaner will have made an assessment of the surface before putting in a quote or starting work.
Then there are the varying conditions across Australia. In the Top End the intensity of storms and the humidity of the wet season present issues you would not find in the dry interior or the colder south. A Melbourne roof might have moss in the shade whereas in humid coastal Queensland the algae will set in fast.
Tiles, Metal And Shingles
With age concrete tiles are prone to becoming weathered and porous if not brittle. If the problem is organic growth, soft washing is the conservative option. One might get away with pressure washing but only with a controlled nozzle and after a thorough inspection.
Terracotta is a strong tile yet the finish can be compromised by too much aggression. Any operator worth his salt will check for signs of movement, cracks or past repairs. Loose tiles mean the roof is not safe to clean.
Asphalt shingles call for care since the pressure can dislodge the granules that protect them. With Colorbond and other metal roofing there is the matter of fasteners, corrosion and scratches to contend with, and a detergent suited to the material. Should the Australian roof in question have a specialist coating then the manufacturer’s word is law.
A Word On Risks
The mistake is to think the filthiest roof calls for the heaviest hand. First and foremost is diagnosis. Algae can make a roof appear dirty, but it could be uneven from poor drainage, failed coatings or tiles on the move.
And the edges are where people are caught out. There is the matter of wall flashings, skylights, vents, downpipes, gutters, valleys and solar panels. Runoff should not be channeled into a rainwater tank nor debris pushed into the gutters.
Pre-Cleaning Safety Checklist
- Make an inspection for gaps, rust, damaged flashing and tiles that are loose, brittle or cracked.
- Postpone in the event of extreme heat, thunderstorms, rain or high winds.
- See to the protection of windows, painted walls, vehicles, gardens, tanks and outdoor furniture.
- Be sure of how the runoff is to be dealt with, whether by dilution or being directed clear of anything sensitive.
- Put in place fall protection, good footwear and an exclusion zone at ground level for safe access.
- Gutters and downpipes are to be cleaned after the roof has been done, barring an earlier inclusion in the service.
Safe Work Australia has official advice on heights. It is no virtue of frugality for a homeowner to scale a slippery roof to avoid a quote; it is an invitation to end up in a plaster cast.
Costs In Australia
Prices for roof cleaning in Australia will be determined by the size and pitch of the roof, the material, the location and the extent of the staining, as well as if there are gutter repairs or cleaning to be had. As things stand, several hundred dollars will see a small, easy to get to roof done; a large one that is steep or badly affected will run you in excess of AUD 1,000.
Get clarification on the quote as to whether it covers the equipment for roof access, rinsing, follow-ups, controls for runoff and the like. A soft wash with a proper inspection and plant protection is not the same as a cheap pressure wash.
Maintenance
In Australia one should not let an arbitrary calendar dictate roof maintenance; the schedule has to be in keeping with local conditions. An exposed roof is a different matter from one in the shade of trees and will not call for as frequent an inspection. Where humidity or the coast is a factor, homes are prone to algae and mould and will want to be put right sooner. Roofs with overhanging branches are candidates for more regular gutter work.
A good routine would be to have a look at the roof from the ground in the wake of a big storm, clear any leaves from the gutters and put in for a professional if you see staining come back in short order. There is no point in cleaning too much but letting organic growth get to the stage where it lifts coatings and holds moisture will cost you.
Hiring A Roof Cleaning Professional
Opt for a licensed cleaner who can set out his approach in plain English. The quote you are given ought to make note of the roof material, what products and pressure will be applied, how access and runoff are to be managed and any exclusions. Should he be unable to tell you what will happen to your rainwater tank then look elsewhere.
You would do well to ask for proof of public liability insurance, safe work practices and the licences or registrations your state demands, as well as experience with the type of roof you have. See if a condition report with photographs is part of the service; such a record is useful in telling pre-existing damage apart from anything that shows up after the clean.
Questions Worth Asking
Find out if pressure washing is something your tiles can take, if sodium hypochlorite is on the cards and in what dilution, how the plants and tanks are to be shielded and the protocol for loose tiles. Inquire as to whether the cleaning will void any warranty or affect protective coatings. Warranties are not all the same so do not take a verbal assurance, get the manufacturer’s guidance.
When time is short and you have only a day to spare, put your efforts into an inspection, unblocking the gutters and dealing with the worst of the organic growth. Do not put a full clean in when the weather is against you or hasten access because of visitors. The roof is not going anywhere and will be there tomorrow to judge you for it.
Frequently Asked Roof Questions
Homeowners tend to put these to us before making a booking. While the answers are straightforward, the final method is down to the state of the roof.
Is Soft Washing Better Than Pressure Washing For Roofs?
For lichen, moss, algae and mould it is. Soft washing applies low pressure to deal with the organic growth. One can use a pressure washer on a sound roof but do it wrong and you risk water ingress, loose tiles and surface damage.
Can You Pressure Wash Roof Tiles In Australia?
Some can be, but it is a question of the finish, age and condition of the tile and what the maker says. Have a professional check for movement, brittleness or cracks before any controlled pressure is brought to bear.
What Is The Safest Way To Clean A Roof?
Have it inspected and go with the least aggressive option that will do the job. On a tiled roof this is usually soft washing with some chemical and a low-pressure rinse, provided there is fall protection and runoff management in place.
How Often Should A Roof Be Cleaned In Australia?
It is not a case of one size fits all. If a roof is under trees or in damp conditions it needs to be seen to regularly and cleaned once the gutters are blocked by established growth. A pro will advise on a schedule that suits the exposure.
Does Pressure Washing Damage Roof Tiles?
Excessive pressure will. It can dislodge a tile, force its way under an overlap, strip a coating or mar terracotta and the weathered face of concrete. The older the tile the more likely it is to be damaged.
How Much Does Roof Cleaning Cost In Australia?
Expect to pay several hundred for a small, easy to get to roof and in excess of AUD 1,000 for a steep or badly stained one. Get an itemised quote as safety gear, treatments and the like will add to the figure.
Can Soft Washing Remove Moss, Mould And Algae?
It will treat and remove most of it though you may have to manually get at thick moss. If the growth is a recurring problem it could be a sign of poor drainage or too much shade.
What Chemicals Are Used In Soft Washing?
There are different systems, some with surfactants and diluted sodium hypochlorite. The cleaner will explain the product and disposal plan before he starts.
Is Roof Cleaning Covered By Australian Roof Warranties?
That is a matter for the terms of the warranty and the product. Some put restrictions on the chemicals or methods used. Make sure you have the current conditions from the manufacturer in writing.
Making The Sensible Choice
Where there is organic staining on an Australian home, soft washing is the prudent first resort. Pressure washing is fine for certain surfaces but it should not be the automatic response.
Use a licensed roof cleaner with the right health and safety controls, inspect the property and tailor the method to the roof. It is the difference between an effective treatment and making a loud mess of the top of the house.
