GK Decking Cleaner 5LTR

Product Description

Why Decking Needs a Dedicated Cleaner: Not Just a Pressure Wash

Decking is one of the most demanding outdoor surfaces to maintain in the UK climate. Unlike stone or concrete, timber is a biological material, meaning it has its own natural chemistry that makes it behave differently from hard mineral surfaces when exposed to moisture, biological growth, and the repeated wet-dry cycles of British weather. These properties make decking particularly susceptible to the kinds of contamination that create real problems beyond surface appearance.

The primary enemy of decking is not dirt, it is biofilm. Biofilm is a thin, slimy layer of living bacteria, algae, and microbial matter that establishes on any consistently damp surface. On decking, it develops within weeks of wet weather and is the direct cause of the slippery, hazardous surface conditions that make decking genuinely dangerous underfoot in rain or frost. Pressure washing removes biofilm temporarily, making the surface clean, visibly bright, and safe immediately after washing. Within weeks, in damp conditions, the biofilm re-establishes from surviving cells and the decking is hazardous again.

GK Decking Cleaner's biocidal chemistry kills biofilm at a cellular level rather than physically removing it. This is why treated decking surfaces remain slip-resistant for significantly longer than pressure-washed surfaces. The biological cause of the slip hazard has been eliminated, not just displaced.

Beyond biofilm, decking is vulnerable to algae, mould, and lichen, which not only stain and discolour the wood but accelerate the biological degradation of timber fibres, shortening the lifespan of the decking if left untreated. Regular treatment with GK Decking Cleaner removes active biological growth and inhibits re-establishment, protecting the timber and extending the maintenance interval between more intensive restoration treatments.

Decking Cleaner and Reviver: The Two-Stage Approach

For decking that is simply in need of an annual clean to remove biofilm, algae, and surface growth present, but the underlying timber still in sound condition, GK Decking Cleaner is the complete solution. Apply, allow to work, and the biological contamination is addressed.

For decking that has been neglected for longer periods, or that shows significant greying, discolouration, or weathering of the timber fibres themselves, GK Decking Cleaner is the first stage of a two-step restoration approach:

Stage 1 - Clean: Apply GK Decking Cleaner to kill and remove all biological growth from the surface. Allow the product to work naturally, with weather cycles progressively clearing dead biological matter from the surface.

Stage 2 - Revive: Once the surface is biologically clean, apply GK Wood Restorer to reverse the UV-induced greying of the timber and restore the wood's natural warm colour and character. GK Wood Restorer reactivates the lignin in weathered surface fibres, returning the decking to close to its original appearance before any protective treatment is applied.

This clean-then-revive sequence is what the market understands as a "decking cleaner and reviver", two distinct products working in sequence to achieve both a biologically clean surface and a restored timber appearance. Both GK Decking Cleaner and GK Wood Restorer are available from the GK Decking Cleaner category. For customers who want to go further, a protective decking oil or sealer applied after restoration locks in the result and provides ongoing moisture and UV protection.

Bleach-Free: The Right Choice for Timber

Bleach-based decking cleaners are common, cheap, and produce immediately visible results. They are also the wrong product for timber. Bleach oxidises the surface fibres of wood, breaking down the natural lignin structure and accelerating the greying and weathering process. Over time, repeated bleach application makes the greying problem worse, not better. The timber's own chemistry is being degraded by the cleaning product that's supposed to maintain it.

GK Decking Cleaner contains no bleach, no acids, no ammonia, and no solvents. It is non-oxidising, which means it acts only on the living biological cells causing the problem such as algae, mould, lichen, and bacteria, and has no interaction with the timber's own cellular structure. Treated timber is cleaned without being chemically degraded, which means the natural appearance of the wood is preserved and the surface remains in better condition for subsequent treatment with oil, stain, or sealer.

The virtually neutral pH of 6 also means this product is safe on composite decking, hardwood decking, and softwood decking equally, without the surface discolouration or bleaching that acid or bleach chemistry can cause on treated or coloured composite boards.

What GK Decking Cleaner Treats on Timber

The product is formulated specifically for timber and composite decking but extends across all outdoor timber structures:

• Softwood decking: pine, spruce, larch, and pressure-treated decking boards, the most common domestic decking type and the most susceptible to green algae and biofilm in UK conditions.
• Hardwood decking: teak, oak, iroko, and other hardwood decking that develops surface algae and mould despite its natural density.
• Composite decking: safe on composite and PVC-capped composite boards, removes green algae and surface biological growth without discolouring or affecting the composite surface.
• Decking steps, handrails, and frame timbers: full treatment of all decking components, not just the boards.
• Garden fencing and timber structures: the same formula treats fencing panels, pergolas, garden furniture, shed cladding, and any other outdoor timber where biological growth is present, with the added biocidal benefit of inhibiting wood-rotting organisms.
• Window frames and exterior joinery: safe on painted and unpainted timber joinery.

How GK Decking Cleaner Works: Kill, Dwell, Weather

GK Decking Cleaner is a natural surfactant biocidal cleaner. On application, it foams vigorously, providing a practical visual indicator which confirms complete surface coverage. Any area that hasn't foamed hasn't received adequate product. For decking applications where it's easy to miss sections between boards, around posts, and at step edges, this foaming behaviour makes thorough coverage straightforward to verify.

The active DDAC biocidal chemistry kills biological growth on contact. The product then works in conjunction with natural weather cycles: UV and dry periods desiccate dead biological matter; rainfall progressively removes it from the surface. For mild algae and biofilm, improvement is visible within a few days.

For heavier biological loading such as established lichen or thick green mould between decking boards, meaningful results develop over two to three months. Subsequent maintenance applications work significantly faster as baseline biological loading reduces with each treatment cycle.

Apply the diluted solution to a dry decking surface in dry conditions. Do not rinse immediately. Instead, allow the product to dry naturally and work with the weather. If access to the decking is needed urgently, wait at least one hour before rinsing with clean water, though natural drying produces the best and most durable results.

One 5-litre bottle of GK Decking Cleaner makes up to 25 litres of ready-to-use solution, treating approximately 100 square metres:

• Heavy soiling (thick algae, established lichen, heavily contaminated decking): dilute 1 part product to 2 parts water.
• Light to medium soiling (general biological growth, routine annual maintenance): dilute 1 part product to 4 parts water.

No specialist equipment is required. A garden pump sprayer handles a full decking area efficiently. The product can also be brush-applied, which is particularly useful for working the product between decking boards where sprayer coverage may be uneven.