How to Soft Wash a Facade: A Step-by-Step Guide

Soft washing is the gold-standard for cleaning the outside of a home. Instead of blasting surfaces with 3,000+ PSI of water, soft washing uses low pressure combined with a biodegradable cleaning solution that kills mould, algae and lichen at the root. The result is a deeper clean that lasts four to six times longer than pressure washing alone — without etching render, splintering weatherboards or forcing water behind cladding.

When to soft wash instead of pressure wash

Soft washing is the right call any time the contaminant is biological (the green, black or grey film you see on shaded walls and eaves) or when the substrate is delicate. Use it on:

• Rendered and painted facades
• Weatherboard, fibre cement and Hardiplank cladding
• Brick veneer and besser block
• Colorbond and metal cladding
• Roof tiles (concrete and terracotta)
• Eaves, soffits and fascia boards

Save the pressure washer for hard horizontal surfaces — concrete driveways, paths and garage floors — where mechanical agitation is needed to lift oil and ground-in dirt.

What you'll need

• Soft wash pump or 12V system (or a downstream injector on your pressure washer)
• Sodium hypochlorite (12.5%) — the active ingredient
• A surfactant designed for soft washing (helps the solution cling to vertical surfaces)
• Garden hose with a good flow rate for pre- and post-rinsing
• Plastic sheeting or drop cloths to protect plants and pavers
• PPE: chemical-resistant gloves, eye protection and old clothes

Step-by-step: soft washing a facade

1. Prep the area

Move outdoor furniture, BBQs, kids' toys and door mats clear of the wall. Close all windows and doors. Cover power points, light fittings and any vents with plastic and tape. Pre-soak garden beds, lawn and pavers within 2 metres of the wall — wet foliage is far more resistant to runoff than dry foliage.

2. Mix the solution

A typical house mix is 2–4% sodium hypochlorite — that's roughly 1 part 12.5% bleach to 2–3 parts water — plus 30–60 mL of surfactant per 10 L of finished mix. Lighter staining gets the weaker mix; heavy mould on a shaded south wall gets the stronger one. Always test a small inconspicuous patch first.

3. Apply from the bottom up

Working in 2–3 m² sections, apply the solution at low pressure (under 200 PSI) from the bottom of the wall upwards. Starting at the bottom prevents 'tiger striping' where clean solution runs down a dirty wall and leaves streaks. Keep the surface uniformly wet for 5–15 minutes — you'll see the green and black contamination turn light or disappear.

4. Agitate stubborn spots

For heavy lichen or 30+ years of build-up, use a soft bristle brush on an extension pole to gently agitate after the dwell time. Never use a wire brush or stiff-bristle scrubber on render or paint.

5. Rinse thoroughly

Rinse the wall from the top down with plenty of fresh water at low pressure. Then re-rinse the surrounding plants, lawn and pavers — a good rule of thumb is 'if you wet it before, wet it again after'.

Common mistakes to avoid

1. Using too much pressure — anything over 500 PSI on vertical surfaces risks driving water behind cladding.
2. Letting the solution dry on the wall — always keep it wet during dwell time and rinse before it cures.
3. Skipping the pre-soak on plants — concentrated bleach on dry foliage will burn it overnight.
4. Working in direct hot sun — the solution flashes off too quickly and leaves residue.
5. Forgetting eaves and the underside of gutters — these are usually the dirtiest part of the facade and the easiest to miss.

How long will the result last?

A properly soft-washed facade in Melbourne typically stays visibly clean for 3–5 years on north-facing walls and 18–30 months on shaded south-facing walls under tree cover. Annual maintenance washes are quick, cheap and stop biological growth from ever taking hold again.