Killing moss on a driveway requires a treatment that attacks the plant at the root rather than simply knocking off the surface growth, which regrows quickly. Several effective products are available, ranging from household bleach to professional biocidal treatments.

Diluted Bleach

A solution of one part household bleach to five parts water applied to moss-covered areas and left to dwell for at least 30 minutes kills moss and algae effectively and inexpensively. The bleach disrupts the cellular structure of the moss and kills it at the base. Apply with a watering can or garden sprayer, ensuring thorough coverage, and then leave the solution to work before rinsing away or pressure washing. Bleach is effective and cheap but can lighten some surfaces and must be kept away from planted borders and drains due to its environmental impact on aquatic organisms.

Ferrous Sulphate

Ferrous sulphate, a mineral compound, is one of the most effective moss-killing chemicals and is sold in concentrated form for dilution before use. It kills moss by reacting with the chlorophyll in the plant, turning it black and dead within days. Ferrous sulphate is widely used on lawns and sports surfaces and is equally effective on hard surfaces. It can stain concrete and stone surfaces orange or brown at the application points, which is worth being aware of before treating light-coloured driveways.

Proprietary Driveway and Patio Cleaners

Commercial driveway and patio cleaners containing biocides such as benzalkonium chloride or didecyl dimethyl ammonium chloride are formulated specifically for hard surface moss, algae, and lichen treatment. These products provide a more targeted treatment than bleach or ferrous sulphate and typically include guidance on dwell times, application methods, and environmental precautions. They are available from garden centres and DIY stores and provide reliable results when used according to the instructions.

After Treatment

After the moss-killing treatment has done its work, the dead growth turns brown or black over the following days to weeks. Pressure washing removes the dead material and clears the surface. On block paving, re-sand the joints after pressure washing to restore joint stability. Applying a post-clean preventive biocide inhibits regrowth and reduces how frequently the treatment needs to be repeated.

Summary

Diluted bleach, ferrous sulphate, and proprietary biocidal cleaners all effectively kill driveway moss. Apply and allow to dwell before washing away. Bleach is cheap but can lighten surfaces. Ferrous sulphate can stain light-coloured surfaces. Proprietary biocides are the most targeted option. All treatments must be kept away from planted borders and drainage systems. A post-treatment preventive biocide slows regrowth.