Biocide Treatment
Cleaning removes what is on the surface today. A biocide kills the spores and root structure left behind, so the green does not come straight back the moment we drive away.
The part that makes the clean last
Ireland's climate is close to ideal for algae, moss and lichen: mild, wet and rarely bright for long. That is why a driveway can look green again within a year of being washed. Pressure removes the visible growth but leaves spores and root filaments in the pores of the surface, and they regrow from there.
A biocide is applied after cleaning, at low pressure, and left to dry rather than rinsed. It works into the surface and destroys the organic material that pressure could not reach. Nothing dramatic happens on the day — the effect is what does not happen over the following two to four years.
We use products approved for their intended surface and apply them at the labelled rate, with planting, drains and water features protected first. On roofs a biocide is often the main treatment rather than an add-on, because it is the only safe way to deal with heavy moss without pressure washing the tiles.
How the treatment is carried out
- Surface cleaned or scraped first — biocide is not a substitute for cleaning
- Planting, drains, ponds and water features covered and protected
- Product selected for the specific substrate and growth type
- Applied at low pressure at the labelled dilution rate
- Left to dry into the surface rather than rinsed off
- Weather checked so rain does not wash it off before it works
- Aftercare guidance and expected timeline explained
- Optional annual top-up visit at a reduced rate
Where it works best
- Tile and slate roofs with recurring moss
- Render, dash and painted walls with black spot
- North-facing and tree-shaded elevations
- Patios, paths and steps that turn green each winter
- Cobblelock driveways and block paving joints
- Timber decking, fencing and pergolas
- Monuments, headstones and stonework
- Commercial walkways where slip risk matters
What a biocide will and will not do
- Kills moss, algae, lichen and mould at the root
- Slows regrowth for roughly two to four years
- Works gradually — surfaces keep improving for weeks
- Does not remove oil, rust, paint or mineral staining
- Does not replace cleaning, it extends it
- Is not a sealer and does not change the surface finish
What it usually costs
| Job | Guide price |
|---|---|
| Added to any exterior clean, per m² | From €2.50 |
| Roof biocide, per m² | From €4 |
| Full house render treatment | From €280 |
| Driveway or patio treatment | From €120 |
| Decking and fencing treatment | From €90 |
| Annual maintenance visit | From €95 |
| Commercial / managed property | Quoted on site |
Biocide Treatment — recent jobs
Biocide Treatment near you
Local pages with the conditions, coverage and questions specific to each area.
Frequently asked
Is a biocide safe for pets, children and plants?
The products are approved for exterior use and are safe once dry, but they are still biocides and are handled accordingly. We cover planting, drains and any pond or water feature before applying, and we ask that pets and children stay off the treated area until it is fully dry — usually a few hours. Tell us in advance about vegetable beds, fish or sensitive planting.
How soon will I see a difference?
Not immediately, and that is normal. The product needs time to kill the growth and rain to wash the dead material away. Most surfaces improve visibly over two to eight weeks, and roofs continue to lighten for two to three months.
How long does it last?
Generally two to four years, depending on how much sun and airflow the surface gets. A south-facing driveway can stay clear for four years or more, while a north-facing wall under trees will need topping up sooner.
Can I just use a biocide instead of cleaning?
On a roof, often yes — that is the standard approach, because pressure washing tiles causes damage. On paving and render, no: a biocide kills the growth but does not remove years of accumulated dirt, so the surface will be dead-green rather than clean. The two work together.
Does it stain or change the surface?
No. It dries clear and does not alter the colour, texture or slip resistance of the surface. It is not a sealer, so it does not leave a film or a sheen.
Can it be applied on its own to a surface you did not clean?
Yes, we are happy to treat a surface someone else cleaned, or one you cleaned yourself. We will look at it first and tell you honestly whether a biocide alone will give you the result you want.
Get a fixed price before we start
Send a few photos or a short description and we will come back with a written, fixed-price quote. No call-out fee, no obligation.