Render cleaning

Here in Aus exterior walls cop a fair beating from the elements:

• Green algae staining and mould growth: Loves damp, shady areas and poor lighting conditions
• Organic growths: Feed on damp, porous surfaces especially without regular cleaning
• Salt: If you’re coastal, salt deposits can cause water marks and surface discolouration
• Fertiliser and bore water: Cause black staining and stubborn stains, often around the base of walls
• Bird droppings: Cause deep stains and are a pain in the backside to remove

Add in windblown dust and surfaces on buildings being left for years without care and you’ve got a recipe for a filthy facade.

Step 1: What Type of Render

Every type of render reacts differently. Your approach depends on what you’re dealing with:

• Coloured render or acrylic? Avoid pressure washer units and stick to soft washing techniques
• Cement renders or lime-based? Mild pressure might be okay, but test a small vertical surface first

Not sure what type of render you have? Send us a pic. Window Cleaning Melbourne Crew can spot a sensitive surface from a mile away.

Step 2: Choose the Right Method

The right process matters more than brute force:

• Soft washing process: Low pressure and composite water to remove organic stains and mould spores
• Chemical solutions and suitable detergents: We use neutral pH and acting product blends for exterior cleaning — no harsh detergents or strong dilutions
• Soft-bristled brush: Perfect for gentle scrubbing of stubborn stains on acid-sensitive surfaces
• Residual biocide protection: Prevents regrowth of green algae and black moulds

*  Avoid harsh cleaners and abrasive brushes — they can damage the render and cause unnecessary damage.

Step 3: Application Techniques

• Cone spray or skilled spray methods: Even flow of chemical across the entire surface
• Topical application and subsequent applications may be needed for heavy staining or deep-set black stains
• Let the detergent sit for adequate dwell time, allowing the activation time to kick in

Step 4: Rinse and Dry

• Use clean water or suitable water to rinse off chemical residues
• Dry surface and adequate drying time before inspecting for any damage

If you want a showroom finish you’ll need to maintain it regularly. Here’s what we recommend:

• Coastal or humid areas: Every 12–18 months due to increased algae from walls and green algae staining
• Inland or dry climates: Every 2–3 years
• High-traffic or shaded spots: More frequent cleaning

*  Watch for black staining and mould growth — they’re your early warning signs that a clean is overdue.

You CAN:

• Use a garden sprayer to apply a gentle detergent
• Scrub gently with a soft brush on unsightly stains
• Stick to vertical surfaces and shaded times of day to avoid streaking

You SHOULDN’T:

• Use a pressure washer unless you’re keen on risking damage
• Rely on harsh chemicals or bleach (especially near delicate plants)
• Attempt cleaning with foul water or during hot conditions

Spring

• Good for removing winter grime and black mould
• Tackle pollen and organic stains on the exterior render

Summer

• Avoid midday cleans; heat dries out chemical solutions too quickly
• Great for applying residual biocide protection to reduce organic staining

Autumn

• Perfect for dealing with damp patches and green algae staining
• Prep your exterior surfaces before the wet rolls in

Winter

• Monitor shaded areas for lichen fungus or biological growth
• Clean periodically when surfaces are cool and damp

Hiring a pro? Here’s what to expect for soft washing render surfaces:

• Small entrance or feature wall: $180-$250
• Standard single-storey home: $350-$700
• Large two-storey or full wraparound: $800 – $1500+

Things that impact price:

• Type of staining
• Type of render
• Application methods required
• Access issues or use of specialist equipment

Render is a popular choice for modern homes but it needs to be cleaned regularly to stay looking sharp. From composite water flow to topical application of biocides, every step counts. Treat your exterior surfaces with care, use the right soft washing technique and don’t fall for gimmicks that promise a 5 minute miracle clean.

Looking to keep your exterior render looking its best? Or have soft washing questions? Contact Window Cleaning Melbourne Crew — we’ll help you protect your investment and get that finish back without causing damage.

Got a wall full of green algae or black staining? Drop us a line or send a pic. We’ll tell you how to fix it or do it for you with no fuss.