When it comes to roof cleaning, there’s a lot of confusion between pressure washing and soft washing — and choosing the wrong method can cause more harm than good.
At Metro Water Blasting, we’ve cleaned thousands of roofs across Auckland, and we can tell you with confidence:
📌 Soft washing is the safest, most effective method for cleaning New Zealand roofs.
Here’s why it matters — and how to avoid damage from the wrong technique.
👉 Learn more about our roof cleaning services
What Is Pressure Washing?
Pressure washing (also called water blasting) uses high-pressure water jets — often 1500–4000 PSI — to blast away surface grime.
While great for concrete and driveways, this method is too aggressive for most roofing surfaces, especially:
- Colorsteel
- Decramastic (chip-coated metal)
- Painted or aged metal roofing
- Concrete tiles
- Membrane or rubber roofs
What Is Soft Washing?
Soft washing uses a low-pressure rinse system combined with a biodegradable chemical treatment that:
- Kills moss, mould, and lichen at the root
- Loosens debris without scraping or blasting
- Rinses gently to preserve roof coatings and tiles
- Prevents regrowth longer than pressure washing alone
👉 Book a soft wash roof treatment here
Why Soft Wash Is Better for Roofs
| Factor | Pressure Wash | Soft Wash |
|---|---|---|
| Pressure level | 1500–4000 PSI | < 300 PSI |
| Moss/lichen removal | Surface only | Kills at the root |
| Paint/coating damage | High risk | No damage |
| Long-term result | Regrowth in months | 12–24 month control |
| Risk of leaks | High on old roofs | None |
Pressure washing strips, cracks, and weakens roofing materials.
Soft washing cleans and preserves.
Roof Types That Should Never Be Pressure Washed
- Decramastic (chip-coated) – Pressure removes protective stone layer
- Colorsteel / Painted metal – High pressure can strip paint and expose metal
- Concrete tiles – May crack under pressure or shift, causing leaks
- Flat membrane roofing – Can puncture or delaminate
Soft wash is recommended by roofing manufacturers for safe moss treatment and general roof cleaning.
The Science Behind Soft Wash Treatments
We use a biocide-based treatment that:
- Breaks down moss, mould, and lichen spores
- Soaks into the surface without forcing water under tiles
- Reactivates with rainfall to extend effectiveness
- Is fully biodegradable and safe when dry
Results improve over time — growth dies off naturally within 2–12 weeks.
👉 Explore moss & lichen removal options
Where in Auckland Is This Most Needed?
Soft wash is ideal in suburbs where moss and lichen grow fast, including:
- North Shore – Albany, Glenfield, Torbay
- West Auckland – Titirangi, Swanson, Massey
- South Auckland – Papakura, Manurewa, Takanini
- East Auckland – Howick, Flat Bush, Botany
- Central – Mount Eden, Sandringham, Epsom
FAQs
Does soft washing leave the moss behind?
➔ Initially yes — it dies off and breaks down naturally over time. No damage, no scraping required.
How long do results last?
➔ 12–24 months depending on shade, roof type, and tree cover.
Can I combine this with gutter or house washing?
➔ ✅ Yes — we offer bundled pricing for full exterior maintenance.
Book Safe, Professional Roof Cleaning in Auckland
Metro Water Blasting uses soft wash treatments on thousands of Auckland roofs — protecting homes, preventing damage, and keeping warranties intact.
✅ Residential & commercial
✅ All roof types
✅ No pressure damage
✅ Fully insured