Quick answer
Results vary with roof pitch, shade, tree cover and local weather. Many treated roofs stay noticeably cleaner for several years, but shaded north-facing slopes may see regrowth sooner.
What you need to know
Biocide slows regrowth rather than preventing it permanently.
Annual visual checks help you plan maintenance before moss becomes heavy again.
Light retreatment or localised cleaning may be enough on subsequent visits.
How David White can help
We assess each property individually before recommending work. For how long does biocide treatment last, that means checking access, roof or gutter condition, and any risks to neighbouring properties.
You can send your postcode and photos for a remote quote in many cases. If the job needs a closer look, we will say so upfront rather than guessing on site.
What to expect on the day
Our team works safely from ladders, towers or MEWPs depending on the building. We protect gardens, paths and driveways where moss or debris may fall, and we clear up when the job is done.
We will confirm timing, access and parking before we arrive so the visit runs smoothly for you and your neighbours.
Next steps
Call 0330 056 7751 or use the contact form with your postcode, photos and a short description of the issue. We cover roof cleaning and gutter work across London, Surrey, Sussex and Kent.