What happens if you leave it
Grey, dull fascia line
White UPVC oxidises and collects atmospheric grime. From the road it reads as 'old house' even when the rest of the property is well-kept.
Green algae on soffits
North-facing and shaded soffits go green with algae fast. The growth holds moisture against the plastic and the fixings behind it.
Ladder marks on render
DIY ladder cleaning leaves rubber scuffs and white scrape marks on render — and risks far worse if the ladder slips on guttering.
Damage from aggressive washing
Hot or high-pressure washing pits and dulls UPVC permanently. The plastic can't be 'un-dulled' once it's been etched.