Protect Paving and Brick from Oak Tannins

If you’ve recently added a green oak pergola, gazebo, or timber frame, you may have noticed dark brown stains on your paving or brickwork. These marks are caused by oak tannins – a natural compound in fresh oak that leaches out when wet. Although harmless to the wood, tannins can leave unsightly stains on porous paving, stone, or brick. The problem is strongest in the first year after installation.

The photos show how tannins from the oak structure have leached out and stained the new paving. Rainwater washed tannins from the timber onto the surface, leaving dark marks on the paving and streaks on the wood. The client hadn’t checked our cover list with recommendations, where we advised covering the whole area with foil for a few weeks to prevent this issue while the oak settled.

Why Oak Stains Paving

• Rainwater washes tannins out of the oak.
• Tannin-rich water runs onto paving or brick.
• Porous surfaces absorb the tannins, leaving stains that are hard to remove.

How to Protect Paving and Brick from Oak Tannins

• Seal the oak with a breathable wood sealer or oil to reduce tannin leaching.
• Seal the paving or brickwork with a quality stone or brick sealer to prevent absorption.
• Improve drainage with drip edges, gutters, or channels to stop tannin-rich water pooling.
• Cover paving temporarily during the first months, especially in heavy rain.
• Clean stains quickly with mild detergent or a tannin remover before they set.

Will Tannin Staining Stop Over Time?

Yes – tannin release reduces naturally as the oak weathers, usually after 12–24 months, meaning stains become less of an issue.