Swiss winters, rain and shady spots take their toll on outdoor stone surfaces. After a few years, slabs turn greenish, joints get mossy and rust rings appear under flower pots. Working in the right order, you can deal with it yourself.
Step 1: Remove algae, moss and green growth
The green film is not only unsightly, it also makes slabs slippery. A pressure washer alone only removes the surface – the spores stay in the pores and the growth soon returns. Too much pressure can also wash out soft stone and joints.
Our AR 50 Algae and Moss Remover works deep down and removes algae, moss, dark discolouration and environmental deposits. It is suitable for natural stone, concrete, ceramics as well as façades and wooden fences. Repeat once a season if necessary.
Important: AR 50 is a strong product. Wear gloves and safety goggles, protect plants and do not let anything get into ponds or watercourses. Follow the safety data sheet.
Step 2: Treat stains specifically
| Stain | Product | Note |
|---|---|---|
| Rust stains (garden furniture, fertiliser, iron in the stone) | RE 76 Rust Remover | Only for acid-resistant stone, e.g. Ticino gneiss such as Serizzo, Cresciano, Calanca |
| Rust on marble or limestone | RM 70 Rust Remover for Marble | Specially for acid-sensitive stone and cast stone |
| White efflorescence, limescale, mortar residues | SF 79 Limescale and Efflorescence Remover | For acid-resistant stone, preferably outdoors |
| Cement haze after laying | ZE 77 Cement Haze Remover | Indoors and outdoors, acid-resistant surfaces |
| Barbecue and oil stains | OE 68 Oil and Stain Paste | Apply, let dry – the paste draws the stain out |
| Tar, bitumen, wax | FE 61 Stain Remover | Indoors and outdoors |
| Graffiti, paint | AP 63 Anti-Graffiti Paste or GE 60 Paint Stain Remover | Also for concrete, mortar and clinker; very effective combined with a pressure washer |
Step 3: Don't forget the joints
Dirty joints make the whole surface look old. Apply ZR 66 Cement Grout Cleaner generously, leave for 10–15 minutes, scrub with the RG 939 Grout Brush with Handle and rinse thoroughly with clean water.
Step 4: Protect it so it stays clean
Once the surface is clean and completely dry, protection is worthwhile. You can read how in our article “Sealing stone”. In short: SB 56 Water Repellent for paving, concrete slabs, clinker and porous natural stone, SB 55 Stone Protection for patios exposed to grease and oil.
Conclusion: first green growth, then stains, then joints – and finally sealing. That way your patio stays beautiful much longer. Large areas or delicate stone? Our team can also take care of the cleaning for you.
