Reviewed and updated March 2026 by Nick Roth, Mould Remediation Specialist, AllAces Cleaning & Restoration
Pressure washing for mould works on hard, sealed outdoor surfaces like concrete, brick, pavers and some cladding. It is the wrong tool for anything porous or indoors, because it drives water into the material and spreads spores instead of removing them.
Used properly, it clears driveways, walls and pool surrounds fast, and a follow-up treatment slows regrowth.
Used on the wrong surface, it strips render, splinters timber, forces water behind cladding and creates the damp conditions mould needs. This guide covers where it helps, where it doesn’t, and how a professional job is done.
Key takeaways
- Outdoor, hard surfaces only. Concrete, brick, pavers, stone and sealed cladding.
- Never indoors. Water and spores end up in wall cavities and carpet.
- Pressure isn't everything. Soft washing with a treatment suits roofs, render and painted surfaces.
- Pre-treat, then wash. A mould treatment with dwell time does most of the work.
- Fix the water. Shade, drainage and leaking gutters bring it straight back.
- Safety matters. High-pressure jets cause injection injuries and fall risks on roofs.
Where pressure washing for mould helps, and where it doesn't
Short answer: the harder and better sealed the surface, the better pressure washing works.
| Surface | Pressure washing? | Better option |
|---|---|---|
| Concrete driveways and paths | Yes | Pre-treat, then wash |
| Brick and stone walls | Yes, at moderate pressure | Check mortar first |
| Pavers and pool surrounds | Yes | Re-sand joints afterwards |
| Painted weatherboards and render | Risky | Soft wash at low pressure |
| Roof tiles | Risky, and a fall hazard | Soft wash by a roof specialist |
| Timber decks | Low pressure only | Deck cleaner and a soft brush |
| Any indoor surface | No | HEPA vacuum, damp wipe, remediation |
How a professional job is done
- Inspect the surface. Check what it’s made of, its condition, and where the water is coming from.
- Protect the area. Cover plants, close windows and isolate outdoor power points.
- Pre-treat. Apply a mould and algae treatment and leave it to work for the label’s dwell time.
- Wash at the right pressure. Use a fan tip and keep a steady distance; match pressure to the surface.
- Rinse and manage runoff. Keep wash water and chemicals out of stormwater drains.
- Post-treat if needed. A residual treatment slows regrowth on shaded surfaces.
- Fix the cause. Clear gutters, improve drainage and cut back shade where possible.
Pressure washing for mould vs other methods
Short answer: pressure washing is one method among several, and only for exterior surfaces.
| Method | Best for | Limits |
|---|---|---|
| Pressure washing | Hard exterior surfaces | Damages soft materials; useless indoors |
| Soft washing | Roofs, render, painted surfaces | Slower; depends on treatment chemistry |
| HEPA vacuum and damp wipe | Indoor hard surfaces | Surface growth only |
| Removing affected material | Plasterboard, carpet, insulation | Needs containment and rebuilding |
| Dry ice blasting | Timber framing, roof spaces, commercial plant | Specialist equipment and cost |
For indoor and building-wide jobs, our guide to commercial mould cleaning methods compares the options, and cleaning mould from porous surfaces explains when material has to come out instead.
Benefits when it's the right fit
Fast on big areas
Driveways and walls take hours, not days.
Safer underfoot
Mould and algae on paths are a slip hazard.
Protects surfaces
Organic growth holds moisture against masonry and paint.
Shows the real problem
Once it's clean, you can see cracks, drainage faults and leaks.
Safety
Short answer: high-pressure water can cut skin and inject water and chemicals into the body. Treat it like a power tool.
- Never point the lance at anyone. Injection injuries can look minor and need urgent care.
- Stay off roofs. Wet tiles and a recoiling lance are a fall risk.
- Wear eye protection, gloves and a P2 mask. Spray carries spores and treatment chemicals.
- Keep power away from water. Use outdoor-rated leads and an RCD.
The NSW Health mould fact sheet explains who is most at risk from spores, and the IICRC S520 standard sets out how professional mould remediation is done.
FAQs
Does pressure washing kill mould?
Not on its own. It removes growth from hard surfaces, but a treatment applied first is what kills the remaining spores and slows regrowth.
Can I pressure wash mould off render or weatherboards?
Only at low pressure, if at all. Soft washing with a treatment is safer for render, paint and timber, because high pressure strips coatings and forces water behind the surface.
Should I pressure wash mould inside the house?
No. Indoors it spreads spores, soaks walls and carpet, and creates more damp. Indoor mould needs containment, HEPA vacuuming and cleaning or removal of affected material.
How often should outdoor surfaces be washed?
Shaded, damp areas often need it every year or two. Fixing drainage, gutters and shade stretches that out a lot.
The bottom line
Pressure washing is a good exterior tool, not a mould cure. Use it on hard, sealed outdoor surfaces, pre-treat first, and fix the water that let the mould grow.
If mould is showing up inside as well, that’s a different job. Our mould removal and remediation team finds the moisture source and deals with it properly.
About the author
Nick Roth, Mould Remediation Specialist, AllAces Cleaning & Restoration
Nick has been with AllAces for more than six years and is our most experienced mould remediation specialist. He completed Decon Systems’ Mould Remediation for Technicians course in August 2021. Technicians in every state we work in call on him for the hardest mould testing and remediation jobs, including work with specialised equipment such as Hydroxyl machines.
