Price Comparison
Let’s talk about costs
To clean a roof with high pressure is expensive
High-pressure roof cleaning in Sydney generally costs between $2300 and $3500+ for a standard residential 3xbedroom bungalow.
A mid-sized home averages between $2800-$4500. Prices usually range from $11 to $20 per square metre, depending on factors like roof pitch, height (single vs. double-storey), and the level of dirt or moss.
Key Pricing Factors in Sydney:
Size
Small homes (<100m²) are roughly $2280-$3150, while larger homes (>200m²) can exceed $3,500.
Accessibility & Pitch
Steep, two-storey roofs require safety gear (harnesses, edge protection), increasing costs. Add another $1500.
Cleaning Method
Extras
Gutter cleaning is often bundled for an extra $320-$500.
For an accurate price, consider:
- The number of storeys?
- How steep is the roof
- What is the condition of the roof with regard to growth,age,
- What is the roof material (tile, metal)?
- Does it have significant moss or grime buildup?
- Do you need gutters cleaned as well?
The one thing people neglect to remember, it is almost impossible to completely remove all of the spores on a roof that cause the infestation of the growths with high pressure only. This is because there are numerous nooks and crannies on a roof high pressure treatment will miss.
Spores are like seeds travelling on a breeze from trees which land on your roof. If the roof is slightly moist, the spores will attach and always prefer the shadier side of the house where moisture prevails.
After the high pressure clean the roof will look sparkling clean but within months because of the missed spores the growth will reappear again.
Which is better to use on roofs a chlorine base product or benzoalkonium chloride?
Comparison Table: Chlorine vs. Benzalkonium Chloride
| Feature | Chlorine (Bleach/Sodium Hypochlorite) | K4 Roof Treatment |
| Speed | Days to weeks | Slow (weeks/months) |
| Results | Removes dark stains immediately | Kills organic growth; washes away with rain over time |
| Residual Effect | Low (regrowth can start quickly) | High (remains on surface to stop regrowth) |
| Safety | Corrosive, harsh on plants/skin | Biodegradable, generally safer |
| Best For | Heavy, infestation | Maintenance and prevention to stay cleaner longer |
1. K4 (The “Safe & Lasting” Option)
This is a quaternary ammonium compound 28% concentration (often called “Quats”). It is the active ingredient.
- Pros: It kills moss, lichen, and algae by breaking down their cell membranes and leaves a residual barrier that prevents new growth for 6–12+ months.
- Cons: It takes time. You spray it and let the rain wash the dead grime away over several months.
- Best for: Tiled roofs (concrete/terracotta), solar panels, and painted surfaces where you want a “set and forget” solution.
2. Chlorine Based Products (The “Instant” Option)
Usually in the form of sodium hypochlorite (pool chlorine) diluted to roughly 1–3%.
- Pros: It breaks down organic material instantly.
- Cons: It can degrade metal roofs (Colorbond) if not used carefully. It is also highly toxic to surrounding plants and landscaping if not rinsed properly.
- Best for: Heavy, thick moss and algae buildup that needs to be removed immediately.
Recommendation Based on Roof Type & Goal
- If you want it clean today : Use a diluted Chlorine-based solution (soft wash method).
- If you want to stop it coming back long-term : Use K4
- For Colorbond/Metal Roofs: K4 is generally preferred because chlorine can accelerate degradation over time.
- Concentrations in many roof cleaners available are quite low(2%-10% . With K4 our concentration is between 28% The difference in application on a roof is its concentration and if you look carefully on labels you will see their REAL concentration