Roof Biocide: How It Works and Is It Safe for Pets, Plants and Ponds?

How a roof biocide works

A biocide kills living organisms on the surface it is applied to, in this case algae, moss, lichen and their spores on the tiles. It is applied at low pressure so it settles into the growth instead of running straight off.

Unlike scraping, which removes what you can see, the biocide reaches spores in the tile surface. That is why treated roofs stay clear longer than roofs that have only been scraped.

Pets

The simple rule is to keep pets indoors or away from the area below the roof while treatment is being applied and until it has dried. Dogs and cats are curious about anything new on the ground, and runoff can collect in puddles near downpipes.

Tell us about pets when you book so we can plan which side of the house to start on and when the garden will be clear again.

Plants and borders

Plants directly under the eaves can be affected if large amounts of runoff fall on them. Covering vulnerable plants, or watering them well beforehand so the soil is less absorbent, reduces the risk. Applying at low pressure and controlling the amount used matters far more than any single product.

Ponds, water butts and wildlife

Ponds and water butts that collect from the roof need particular care, because they take runoff directly. Water butts should be disconnected or diverted before treatment so the first rain after the job does not fill them with treated water.

Ponds under the eaves should be covered during application. Let us know about either when you ask for a quote so the job can be planned around them.

Neighbours and shared areas

On terraced and semi-detached homes, runoff and overspray need to stay on your roof. Working in suitable weather, on still days, and at low pressure keeps the treatment where it is meant to be. If a neighbour has a pond or water butt near the boundary, it is courteous to let them know too.

What a good contractor should ask you

Expect questions about pets, ponds, water butts, nearby plants and whether rainwater is harvested. A contractor who asks none of these is not thinking about where the treatment goes after it lands.

Why low pressure helps containment

Applying treatment at low pressure means it lands where it is aimed and settles into the growth rather than bouncing off as fine mist. That is better for the roof and for everything below it. High-pressure spraying creates drift that can carry onto cars, windows, plants and neighbouring property.

Cars, windows and outdoor furniture

Move cars away from the eaves on the day if you can, and bring in cushions and anything left on the patio below the roof. Windows should be closed while the side of the house next to them is treated. These are simple steps, and we will remind you of them when we confirm the job.

Telling neighbours

If the roof edge is close to a neighbour's garden, a quick word beforehand is courteous. They may want to move washing, garden furniture or a pet bowl for the day. We plan the work so treatment stays on your roof, but neighbours appreciate being told.

Treatment and rain

Treatment needs time to settle before heavy rain. We watch the forecast and avoid applying it when a downpour is due.

Get a quote with your garden in mind

Mention any pets, ponds or water butts when you contact us and we will plan the work around them. Quotes are free across Hampshire, Surrey and Sussex.