Tannin - Decking/Timber

Removing Tannin Stains from Decking & Timber Surfaces

Tannin stains are a common issue on outdoor timber, including decking, fences, pergolas, and other wooden structures exposed to the elements. These stains usually show up as brown, yellow, or dark patches, making the timber look weathered or uneven.

Though tannin stains may look like dirt or watermarks, they are caused by natural compounds in the wood or nearby plant matter. Thankfully, with the right product, tannin stains can be safely and effectively removed without damaging the timber.

What Causes Tannin Stains on Timber?

Tannins are organic compounds naturally found in wood and many plants. When moisture or rain contacts timber or plant debris, these tannins leach out and stain the surface.

Common causes include:

• New or untreated timber: Fresh decking or fencing often has high tannin levels, especially hardwoods like oak, cedar, and redwood.
• Fallen leaves and plant debris: Decaying leaves, twigs, and bark release tannins that stain timber, especially in damp conditions.
• Overhanging trees or vegetation: Rainwater running off leaves and branches carries tannins onto wood surfaces.
• Wood treatments or oils: Some oils or stains can cause tannins to leach out during or after application, resulting in dark patches.

Tannin stains are most visible on lighter woods but can affect all timber types if left untreated.

How to Remove Tannin Stains Safely

Use a specialist tannin remover formulated to lift stains without harming timber fibers or finishes. Avoid harsh cleaners, especially bleach or acidic products, which can dry out wood, cause cracking, or damage protective coatings.

A professional tannin remover will:

✔ Break down and remove tannin stains effectively without damaging the wood
✔ Be safe for treated and untreated timber, including decking, fences, and cladding
✔ Preserve the natural look and texture, avoiding discoloration or surface wear

Most tannin stains come out with one treatment, though older or heavier stains may need a second application for best results.

Preventing Tannin Stains on Timber

While tannin stains can be treated, good maintenance reduces recurrence:

✅ Seal or oil timber surfaces to limit tannin leaching and protect against external stains
✅ Keep decking and fencing clear of leaves and debris by sweeping regularly, especially after rain
✅ Rinse wood after storms or leaf fall to wash away plant matter before stains set

Tannin stains are natural but manageable on decking and timber. Using specialist tannin removers safely restores wood’s clean, natural look without damage.

With regular care and timber-safe products, your outdoor woodwork will stay fresh, vibrant, and free from stains and weathering effects.