Using a stiff broom to scrub moss off your roof might seem like a quick fix, but it can actually damage your roofing material and puts you at serious risk of a fall. There are safer, more effective methods suited to New Zealand's damp climate — and knowing the difference could save your roof and your health.
Why Moss Is Such a Problem on NZ Roofs
New Zealand's humid, temperate climate — particularly in regions like the Waikato, West Coast, and Northland — creates ideal conditions for moss, lichen, and algae to take hold on roofs. Over time, moss retains moisture against your roofing surface, which can accelerate deterioration of concrete tiles, terracotta tiles, metal roofing, and asphalt shingles. Left untreated, it can lead to leaks and costly repairs.
Regular maintenance is important, and BRANZ recommends periodic roof inspections and cleaning as part of good building upkeep.
The Problem With a Stiff Broom
While it's tempting to grab a stiff broom and start scrubbing, this approach carries real risks:
- Tile and coating damage: Aggressive scrubbing can dislodge granules from coated tiles, crack aged concrete tiles, or scratch metal roofing, shortening the roof's lifespan.
- Spreading spores: Dry-scrubbing can scatter moss and lichen spores across your roof and into gutters, making regrowth worse.
- Fall hazard: Working on a roof is one of the leading causes of serious injury and death in New Zealand. WorkSafe NZ classifies roof work as high-risk, even for short tasks.
- Wet surfaces: Moss makes roofing extremely slippery. A broom gives you poor balance and little control.
If you do choose to do any roof work yourself, always use a properly secured ladder, wear non-slip footwear, and ideally use a roof ladder or crawl board to spread your weight. Never work alone.
Safer Methods for Removing Moss
1. Chemical Moss Treatment (Low-Risk Option)
The safest DIY approach is applying a moss and mould treatment from ground level or with minimal roof access. Products designed for roofs are widely available at Bunnings and Mitre 10. These treatments kill moss over several weeks, after which it dries out and can be rinsed or blown away naturally by rain.
Always follow the manufacturer's instructions and check that the product is suitable for your specific roof type (metal, tile, etc.). Be mindful of runoff into gardens or waterways — many products contain biocides.
2. Low-Pressure Washing
A low-pressure wash (not a high-pressure water blaster) can help loosen dead moss after chemical treatment. High-pressure water blasting is generally not recommended on tiled roofs as it can force water under tiles and damage coatings. If you're unsure, this is best left to a professional.
3. Soft Brush or Leaf Blower (After Treatment)
Once moss has been killed by a chemical treatment and has dried out, a soft-bristled brush or leaf blower can help clear the debris — but again, working safely at height is the priority. A long-handled soft brush used from a ladder (rather than walking on the roof) is preferable to a stiff broom used directly on the surface.
4. Preventive Zinc or Copper Strips
Fitting zinc or copper strips along the ridge of your roof is a well-established preventive measure. Rainwater washes trace amounts of metal down the roof, inhibiting moss and algae growth. This is a longer-term solution worth considering after a clean.
Roof Safety: What You Must Know
Under the Health and Safety at Work Act 2015, even homeowners have a duty of care to themselves and others. Falls from roofs are a leading cause of serious injury in NZ. Before going anywhere near your roof:
- Assess the pitch — anything steeper than about 15–20 degrees is significantly more dangerous.
- Check the condition of the roof surface (wet moss = extremely slippery).
- Use appropriate fall protection or restraint where possible.
- Tell someone you're working at height.
For most homeowners, the honest answer is: roof cleaning is best left to a professional who has the right equipment, training, and insurance.
Roof Coatings After Cleaning
Once your roof is clean, it's a good time to consider a roof paint or protective coating to extend its life and improve appearance. Quality roof paints from Resene or Dulux are formulated for NZ conditions and can include moss and mould inhibitors. A professional roof painter can advise on the right product for your roof type.
When to Call a Professional
Call a qualified roof painter or roof restoration specialist if:
- Your roof is steep, high, or difficult to access safely.
- The moss coverage is extensive or has been there for years.
- You notice cracked, broken, or slipping tiles during inspection.
- You want the roof cleaned and painted or recoated in one job.
- You're unsure what type of treatment is safe for your roofing material.
A professional will have the correct safety equipment, appropriate cleaning methods, and knowledge of which products suit your specific roof. You can find qualified local roof painters on tradedirectory.co.nz.
Master Painters NZ member
Licensed Building Practitioner (LBP)
Roofing Association of NZ (RANZ)
