Algae growth with limescale deposits outdoors

Outdoor terrace or facade where green algae grows alongside white calcium/mineral deposits from water runoff

Why order matters

When two problems appear together, the treatment order is critical. Using the wrong product first can spread stains, neutralise chemicals, or cause new damage. Follow these steps in order.

Treatment Steps

1. Step 1: Algae Moss

   Product: Lithofin ALGEX

   Why this order: Algae forms a biological layer that prevents limescale treatment from reaching the mineral deposits. Algae removal also uses alkaline chemistry which should come before acid.

   Method: Apply ALGEX diluted as directed. Leave 24 hours for maximum effect. Remove dead algae with stiff broom or pressure washer (max 80 bar, 30cm distance). Rinse thoroughly.

   Wait: Wait 2-3 days for surface to dry completely

2. Step 2: Limescale

   Product: Lithofin MN Builders' Clean (diluted) or CEMENT-AWAY

   Why this order: Mineral deposits are now exposed. Acidic treatment can work directly on calcium without being blocked by organic growth.

   Method: Pre-wet surface. Apply diluted product (1:5 to 1:10 depending on stone sensitivity). Leave 5-10 minutes. Scrub, rinse thoroughly.

   Wait: Apply protective treatment (Stain-Stop or Outdoor Sealer) after 48 hours

Warnings

• On calcareous stone (limestone, bluestone): use very diluted acid and test first
• Pressure washing alone does not kill algae roots - chemical treatment prevents regrowth
• Apply in dry weather, temperature above 5°C