Blast Away Guys provides residential and commercial roof cleaning across Whangārei, Northland and the Bay of Islands. We have cleaned 9,339+ jobs, from family homes and small sheds to commercial roofs the size of 12 rugby fields.
We offer two roof-cleaning methods. A professional roof treatment kills moss, mould and lichen, then lets the sun and rain gradually clear the dead growth. A roof wash removes visible growth during the visit and is better when an immediate result is needed or the roof is being prepared for painting.
For routine maintenance, most dirty roofs do not need to be washed. Treatment is often the gentler and more affordable option. It uses far less water and avoids unnecessary washing of the roofing surface.
For Auckland homes and commercial properties, visit our Auckland roof cleaning page.
Where washing is needed, we use soft washing methods to clean the roof gently without unnecessary high pressure.
Best for routine roof cleaning, preventative care and customers who can wait for gradual results
Growth dies and clears gradually with the sun and rain
Improvement often becomes visible within 2 to 3 months, but complete clearing can take much longer
Uses much less water than a roof wash
Usually the more affordable option
The treatment remains on the roof and continues working
Best for painting preparation, pre-sale presentation or anyone needing an immediate visual result
Visible growth and grime are removed during the visit
The visual improvement is immediate
Uses considerably more water than a roof treatment
Usually more expensive because it takes more labour, time and equipment
We apply an included follow-up treatment after washing to help deal with remaining spores and slow regrowth
A roof treatment is applied to the roofing surface to kill moss, mould and lichen. It is not rinsed off. Sunlight and rain gradually break down and remove the dead growth.
Moss, mould and lichen can behave like a wet towel left across your roof. They hold moisture against the surface after the rain has stopped. Over time, this can stain or damage protective coatings and roofing materials.
You will often notice moss and lichen changing colour within the first 2 to 3 months. Moss and lichen can take up to 12 months to clear. Heavy black mould can take up to 18 months. Every roof responds differently
A single treatment is generally suitable for a roof with light moss, mould or lichen.
Heavy lichen, black mould or more established growth usually needs a dual treatment. This means the roof, or the heavily affected parts of it, receives a second application during the same visit.
If a roof has extremely heavy lichen or black mould, we may also recommend a gel treatment during the same visit. The gel remains on heavily affected areas for longer.
Not every part of a roof is affected equally. The main roof surface may have light growth while the ridges have heavy lichen. In that situation, the lightly affected areas may need one application while the ridges receive two.
Our technicians inspect the roof before beginning. If its condition is different from what was expected when the quote was prepared, we will discuss the recommended treatment with you before proceeding
No. The product used is only one part of a successful roof treatment.
The result also depends on:
Whether the solution is mixed at the correct strength
Whether enough treatment is applied
The type and severity of the moss, mould or lichen
Whether heavily affected areas need a second application during the same visit
The roofing material and its condition
The experience of the person assessing and treating the roof
A strong product can still produce a poor result if it is over-diluted or applied too lightly. A roof with heavy lichen or black mould also needs a different approach from one with only light growth.
Before starting, we assess the roof’s condition. We then select the treatment strength needed for the type and severity of growth
We usually recommend a roof wash when:
The roof is being prepared for painting
The property is going on the market soon and needs an immediate visual improvement
The customer does not want to wait for a roof treatment to work gradually
Heavy black mould or lichen needs to be removed immediately
The washing method depends on the roofing material, pitch, age and condition. After the roof has been washed, we apply an included follow-up treatment. Washing removes visible growth. The treatment helps deal with remaining spores and slows regrowth
There is no single timeframe that applies to every roof. Regrowth depends on the environment surrounding the property.
A roof may need attention more often if it:
Is shaded by trees or nearby buildings
Has a south-facing area that receives less sun
Has a low pitch and stays damp for longer
Collects leaves, pollen, bird droppings or residue from nearby trees
Is made from a porous or textured roofing material
Is exposed to coastal salt or airborne pollution
Some roofs need a treatment every year or two. Others may remain clear for three years or longer. We can recommend a maintenance interval after seeing the roof and its surroundings
Mould produces microscopic spores that travel through the air. These spores can settle on other damp or shaded surfaces around the property.
If the house roof has mould or lichen, it is sensible to check nearby garages, sleepouts, sheds and other buildings. Airborne spores may already have settled on those roof surfaces.
We also regularly see mould and lichen on the roofs of caravans, campervans and motorhomes parked near affected buildings. These roofs are worth checking when the permanent buildings on the property are assessed
If your roof supplies a drinking-water tank, the downpipes must be disconnected before treatment. They must remain disconnected until the roof has received at least 30 mm of rainfall.
If you need help disconnecting the tank, please tell us before the visit. Where disconnection is not practical, we can quote to install a manual downpipe diverter
The safest approach depends on the roofing material and its condition. We generally recommend treatment instead of washing for clay, slate and concrete tiles. Tiles may be loose or brittle. Pressed-metal tiles can also dent if walked on incorrectly.
Long-run metal, Colorsteel and painted roofs are assessed for age, coating condition, corrosion and fixings before work begins. Older or fragile clear roofing can hold staining within the material, so a perfect result is not always possible
Roof cleaning involves working at height and on surfaces that may be slippery. Our technicians use the access and fall-protection equipment required for the roof and site. Blast Away Guys has held SiteWise safety accreditation for seven years, including five consecutive years at Gold level
The price depends on the roof area, pitch, height, access, roofing material and amount of growth. A roof wash costs more than a treatment because it normally requires more time, water, labour and safety equipment.
Send us the property address and clear photographs if you have them. We will recommend the option that suits the roof and your end goal
Blast Away Guys has cleaned 9,339+ jobs across Northland and Auckland. Our work ranges from family homes and sheds to schools and very large commercial buildings. We provide clear advice before work begins and realistic expectations about how long a treatment may take
One commercial property owner had been paying $7,217 each year to have a large roof washed. We showed the owner examples of other large and small commercial roofs we had maintained with treatment rather than repeated washing.
Treating that roof cost $2,362.81.
That was a saving of $4,854.19 in one year.
It also used much less water and placed less strain on the roofing surface. We do not recommend treatment simply because it is cheaper.
We recommend it because, for routine maintenance, it is often the gentler and more practical option.
A roof wash still has an important place when a customer needs an immediate visual result or the roof is being prepared for painting. The end goal should decide the method, not the assumption that every dirty roof needs washing.
Request a quote and tell us whether you want a gradual, cost-effective treatment or an immediate roof wash. If you are unsure, send us the address and photographs. We will help you choose
If your roof has severe black mould or thick lichen growth, washing is the only way to get an immediate improvement. Treatment alone won’t break it down fast enough. In these cases, we recommend a roof wash followed by our treatment to both clean and protect.
With the added treatment, most roofs stay looking fresh for 12 months or more. The exact timing depends on location, shade, and roof type. The treatment we apply after the wash continues working for months, helping to slow down the return of moss and mould.
A wash removes the visible growth, but it doesn’t kill the spores buried deeper in the surface. That’s why we always apply a follow-up roof treatment after every wash. This helps prevent moss and mould from coming back quickly and gives you longer-lasting results from your investment.
No. We use a low-pressure soft washing method never high-pressure blasting to safely clean your roof without cracking tiles or stripping protective coatings. It's safe for most roofing types including concrete tiles, longrun metal, and Colorsteel. Our technicians are trained to adjust their approach depending on the surface and condition of your roof.
A roof wash gives you instant results. It removes visible moss, mould, grime, and lichen right away using a soft wash system. A roof treatment, on the other hand, is sprayed on and works gradually with the sun and rain over time. The roof wash delivers a dramatic visual improvement on the day, while the follow-up treatment we include helps prevent regrowth.
Yes. If you're selling your home, we can provide a Completion of Works Certificate confirming the treatment has been applied. It’s a great document to pass on to your real estate agent or potential buyers for peace of mind.
Yes. Our treatment is biodegradable, non-corrosive, and free from harsh acids or salts. We apply it carefully using professional Venturi systems for even coverage and optimal penetration. No runoff into your garden, no damage to tiles, flashings, or fixings.
We recommend our dual-treatment option. It includes two coats applied in one visit. The first to open up the spores, the second to penetrate deeper and kill more thoroughly. It’s only 20% more than the standard quote and well worth it for heavily affected roofs.
We apply a biodegradable treatment that works with the weather over time. It’s absorbed into moss, mould, and lichen, and then gradually breaks them down through sunlight and rain. No water blasting, no scrubbing, no risk of damage just science and patience doing their job.
In most cases, no especially with modern windows and weather-tight joinery. But if your home has old wooden windows or perished seals, some water seepage can happen. In those cases, we recommend placing old towels or rags along the inside sills as a precaution. We always work with the grain of the house and avoid forcing water into gaps, but we can’t 100% guarantee a watertight outcome in vulnerable spots. If we notice anything concerning before we start, we’ll let you know.
9 times out of 10, we do not require scaffolding. Our guys will use a fall arrest system with harnesses and strops to wash the roof. They are fully trained at Working at Heights and using the fall rest systems. Here is some information about roof washes.
As a general rule, we don’t recommend water blasting tiles as they are often loose and water blasting can blow them off the roof which breaks them. The gentlest and cheapest option to get your roof clean is a roof treatment. If for some reason you really need to wash we will come and take a look at it and assess whether or not it is an ok candidate for a wash
If you are on tank water you will need to disconnect the tanks prior to us arriving. They will need to stay disconnected until there has been 30 mm of rainfall. If you need help disconnecting the tanks please let us know.
The treatment product we use is 100% water-soluble. This means that the rain will wash it away even on a porous surface. To be really safe we recommend that water tanks stay disconnected until there has been 30 mm of rainfall.
A roof treatment involves spraying a product onto the roof surface which kills lichen, moss and mould. The product we use works by killing off the growth and spores and then the rain and sun gradually break down and remove the dead lichen, moss and mould. This process can take up to 12 months or in some cases where there is a thick covering of black mould up to 18 months. Generally, results can usually be seen in the first 2 to 3 months with the moss and lichen changing colour.
Some roofs will remain free of growth for up to 3 or four years and others will need to have an annual or biannual treatment it just depends on the roofing material and the environmental factors that surround the roof. For example, if there are large trees nearby this can cause moss and mould to grow more quickly. Commercial roofs generally need treating every year as they often do not have much of a pitch and so moulds and lichens tend to attach its self and grow better.
Choose house washing, roof treatments, bug treatments, chimney sweeping and more, all in one visit.
Most customers save 10-15% by bundling services and off peak savings can reach 30-35%.
See bundle pricing and packages.
