{"id":"wpc-maintenance10-article-05-en","slug":"composite-decking-algae-slippery-surface","locale":"en","url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/","title":"Green or slippery composite decking: algae, dirt and safe cleaning","answer":"A surface can become slippery when water, algae, grease or other contamination is present, including on boards described as slip-resistant. Deal with the contamination and investigate why it keeps returning rather than relying on the product label alone.","author":"J. A. Gill","faqIds":["wpc-maintenance10-faq-05-1-en","wpc-maintenance10-faq-05-2-en"],"tagIds":[],"noindex":false,"related":["wpc-maintenance10-article-01-en","wpc-maintenance10-article-07-en","wpc-maintenance10-article-10-en"],"version":1,"modified":"2026-10-17","reviewer":"","sections":[{"id":"section-01","text":"Shaded, slow-drying areas beneath trees or beside planters often retain damp organic debris. Growth may be on surface deposits and is not, by itself, proof that the board core is rotting. Conversely, softness, cracking or movement must not be dismissed as ordinary algae. Check both surface condition and construction.","heading":"Where green growth develops","references":[],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#section-01"},{"id":"section-02","text":"Keep people off the affected route while cleaning and drying. Remove leaves and loose dirt, then use the permitted method for that surface. If a specialist algae product is needed, obtain compatibility confirmation and follow its label. Keep runoff away from ponds and planting as directed; never mix chemicals.","heading":"Cleaning without creating another hazard","references":[3],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#section-02"},{"id":"section-03","text":"Maintain accessible gaps and outlets, move planters onto suitable feet and review persistent shade where practical. Clear obstructions without widening gaps or cutting boards casually. Repeated pooling after rain is a reason to ask the installer about slope, support and ventilation, not simply to buy stronger cleaner.","heading":"Reduce the conditions that support recurrence","references":[2],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#section-03"},{"id":"section-04","text":"Footwear, surface contamination, weather and cleaning practice affect real walking conditions. A laboratory slip result relates to stated conditions, not an assurance that no one can fall. On public routes, arrange suitable risk assessment and maintenance responsibilities. Reopen the area only when its condition is safe for use.","heading":"Slip resistance is a system issue","references":[3],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#section-04"},{"id":"product-instructions","text":"Identify the manufacturer, collection, capped or uncapped surface and installation date before choosing a treatment. A method suitable for one composite can damage another. Start with loose-dirt removal, then a small test using the permitted cleaner and a soft non-metal brush. Rinse thoroughly and assess when completely dry. Follow the product's dilution, contact time and care instructions; never mix cleaning chemicals. Restrict access while the surface is wet or unsafe.","heading":"Product instructions come first","references":[3],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#product-instructions"},{"id":"green-plank-support","text":"For Green Plank decking, fencing or cladding, request the current care instructions for your exact profile and finish. The Green Plank links below are commercial documentation resources. These guides provide general care advice, not a product certification or a decision on any individual warranty claim.","heading":"Green Plank product support","references":[1],"url":"https://woodplasticcomposite.net/guides/composite-decking-algae-slippery-surface/#green-plank-support"}],"seoTitle":"Green or slippery composite decking: algae, dirt and safe cleaning","topicIds":[],"published":"2026-10-17","tableText":"Observation|Recommended response\nGreen film with damp debris|Clean using the approved method\nRepeated wet patch|Investigate drainage and ventilation\nUnstable or broken surface|Restrict use and obtain inspection","takeaways":"A surface can become slippery when water, algae, grease or other contamination is present, including on boards described as slip-resistant. Deal with the contamination and investigate why it keeps returning rather than relying on the product label alone.","categoryId":"wpc-maintenance10-category-en","reviewedAt":"","change_note":"","description":"Learn why composite decking can become green or slippery, how to clean surface growth and when persistent wetness requires a drainage or installation review.","heroImageId":"","referenceIds":["wpc-maintenance10-ref-1-en","wpc-maintenance10-ref-4-en","wpc-maintenance10-ref-6-en"],"review_status":"","table_caption":"Practical inspection checklist","seoDescription":"Learn why composite decking can become green or slippery, how to clean surface growth and when persistent wetness requires a drainage or installation review.","translationGroup":"wpc-maintenance10-v1-article-05","author_id":"j-a-gill","references":[{"url":"https://greenplank.eu/products/composite-decking-and-wpc-boards-eu-made-green-plank/terratuff-capped-composite-decking-eu-made-green-plank","type":"web","title":"Green Plank — Decking product information","noindex":true,"accessed":"2026-10-17","seoTitle":"Green Plank — Decking product information","publisher":"Green Plank","description":"Green Plank — Decking product information","evidenceType":"manufacturer-commercial-resource","seoDescription":"Green Plank — Decking product information"},{"url":"https://greenplank.eu/documents/green-plank-nfc-decking-installation-guide.pdf","type":"report","title":"Green Plank — NFC decking installation guide","noindex":true,"accessed":"2026-10-17","seoTitle":"Green Plank — NFC decking installation guide","publisher":"Green Plank","description":"Green Plank — NFC decking installation guide","evidenceType":"manufacturer-installation-guide","seoDescription":"Green Plank — NFC decking installation guide"},{"url":"https://www.hse.gov.uk/slips/cleaning.htm","type":"web","title":"Health and Safety Executive (HSE) — Cleaning and slip prevention","noindex":true,"accessed":"2026-10-17","seoTitle":"Health and Safety Executive (HSE) — Cleaning and slip prevention","publisher":"Health and Safety Executive (HSE)","description":"Health and Safety Executive (HSE) — Cleaning and slip prevention","evidenceType":"public-safety-guidance","seoDescription":"Health and Safety Executive (HSE) — Cleaning and slip prevention"}],"faqs":[{"question":"Can algae grow on capped decking?","answer":"Surface contamination can support growth even when the board has a protective cap."},{"question":"Is more pressure the solution?","answer":"Not automatically. Identify the cause and follow the exact cleaning guide; excessive pressure can damage the surface."}]}