UPVC and Fascia Boards: Why They Go Grey and How to Fix It
Those grey and green streaks on your fascia aren't just dirt — they're algae and atmospheric pollution. Here's why bleach makes it worse and what actually works.
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The Direct Answer
Why do UPVC fascias go grey? The grey and green streaks are algae and dirt from the air, not normal dirt. Bleach is the worst thing to use — it slowly yellows the plastic. The right fix is low-pressure cleaning with a gentle biocide made for UPVC. That kills the algae and keeps the plastic safe. Clean fascias stay clean for 18–24 months in Essex.
What Causes Grey and Green Streaks on Fascias
The discolouration on your UPVC fascia boards isn't simple dirt. It's a combination of algae, polluted air, and environmental grime. In Essex, we're dealing with diesel particulates from traffic, lichen spores carried on coastal winds, and airborne pollution that settles on any exposed surface. Over time, this builds into visible streaks and patches that make your home look older than it is. The problem is worse on north-facing fascias because they stay damp longer and get less direct sunlight. Once algae gets a foothold, it spreads quickly.
Why Bleach Makes It Worse Over Time
The instinct is understandable — bleach kills algae fast. But it's the wrong choice for UPVC. Bleach oxidises the UPVC surface, causing it to yellow and become brittle. You kill the algae today, but tomorrow your fascia is weaker and more discoloured than before. Within a year, the boards start to warp, crack, or split. Homeowners in Harlow and Braintree have learned this the hard way — they've scrubbed with bleach, seen their fascias fade and soften, and ended up paying for replacement years earlier than needed.
What a Proper UPVC Specialist Does Differently
A proper UPVC cleaner doesn't use bleach or high pressure. We use low pressure with specialist UPVC-safe cleaning solutions that are pH-neutral and biocide-based — they kill algae and lichen at the root without damaging the plastic. The process takes longer than bleach, but the result is clean fascia that stays intact and maintains its colour for years, not months.
How Often Do Fascias Need Cleaning in Essex?
In Essex, we recommend professional UPVC cleaning every 18 to 24 months. The coastal damp and constant polluted air mean your fascias are under attack more than in inland areas. Southend-on-Sea and Colchester see more frequent regrowth because of salt spray and moisture. Heavily shaded fascias under trees may need cleaning every 12 months. In open, sunny areas, you might stretch to 24 months or beyond.
What Happens If You Ignore It
Algae and lichen are living things. They eat into the UPVC slowly, weakening it from the surface inward. UV damage compounds the problem — the sun breaks down the plastic further, making it more vulnerable to splitting and warping. After five or six years of neglect, your fascia boards are compromised enough that they start to crack or lift. Water gets behind them and damages the wooden backing boards and soffit underneath. In Billericay and Wickford, we've seen properties where owners ignored their fascias until they had to replace them entirely. Prevention is always cheaper.
Can You DIY Clean Your Fascias?
You can try, but it's risky. Pressure too high damages the plastic. Cleaning solutions designed for other surfaces can oxidise UPVC. Climbing a ladder to reach high fascias is hazardous. Most homeowners end up spending money and time and still don't get the results they expected. A specialist has the right equipment, the right products, and the insurance to do it safely.
FAQ: Will Cleaning Damage the Seal Between My Fascia and Gutter?
Not with our method. Low-pressure cleaning doesn't disturb the gutter seals or joints. In fact, cleaning regularly prevents algae from working into those joints and degrading the sealant, which is what causes leaks. We check the condition of the seals while we're there and flag anything that needs attention.
FAQ: Can yellowed UPVC be restored to white?
Mild yellowing from oxidation can be brought back much with specialist UPVC restorer products. Deep yellowing from years of bleach exposure is permanent — replacement is the only fix. Professional cleaning at the first sign of streaking prevents this entirely.
FAQ: How often should UPVC fascias be cleaned in Essex?
Every 18-24 months for most properties. Coastal Essex (Southend-on-Sea, Burnham-on-Crouch) sees faster regrowth and may need annual cleaning. North-facing or heavily shaded fascias also benefit from annual treatment.
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Written by our team
Owner, Essex Moss Removal · Essex
Our team has cleaned driveways, roofs, patios and gutters across Essex for years. Every job done personally — no subcontractors, no shortcuts. Fully insured and fully insured.
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