Tannin Bleed: What It Is and How to Avoid It

You've just finished a beautiful new deck or timber facade. Then it rains, and brown streaks run down the wall or across the paving. That's tannin bleed. It's natural, it's temporary, and with a bit of planning it's easy to manage.

WHAT ARE TANNINS?

Tannins are natural extractives found in most timbers. They help protect the wood from decay and insects. They're also water-soluble, so when new timber gets wet, they wash out as a brown, tea-coloured run-off.

WHICH TIMBERS BLEED THE MOST?

Most Australian hardwoods bleed when new, including Spotted Gum, Ironbark and Blackbutt. Darker, denser timbers and green (unseasoned) timber tend to bleed the most. Western Red Cedar also has natural extractives that can mark light surfaces.

WHAT GETS STAINED?

Light-coloured and porous surfaces cop it the worst: concrete, pavers, natural stone, render and block walls. Decks over concrete and battens above a rendered wall are the usual trouble spots.

HOW LONG DOES TANNIN BLEED LAST?

The heaviest bleed happens in the first few rains, and it normally settles down within about 3 months. Some timbers can keep releasing a little tannin for up to 12 months.

HOW TO AVOID TANNIN BLEED STAINS

• Seal or cover nearby surfaces before the timber goes up. A concrete or stone sealer, or plastic sheeting, makes a big difference.

• Plan where the water goes. Use flashings, gutters or a garden bed to catch the run-off before it reaches paving or render.

• Pre-oil your timber. Pre-oiling with Cutek CD50 helps reduce tannin bleed, although it won't stop it completely. Cutek is a deep-penetrating oil, not a plastic film that sits on top. It soaks into the timber and repels water from the inside, while still letting the wood breathe and move naturally. Less water soaking in means fewer tannins get flushed out to the surface. We can pre-oil your boards before delivery, on all four sides. Once boards are cut to length on site, seal the cut ends with a tin of Cutek CD50. End grain soaks up the most water, so it's where a lot of the bleed comes from.

• Store timber undercover and off the ground before it goes up.

• Clean up early. Fresh marks are much easier to remove than old ones.

HOW TO REMOVE TANNIN STAINS

Our Grey Deck Cleaner is an oxalic acid cleaner. It removes tannin marks from timber and brings back its natural colour. Oxalic acid can also be used on concrete and stone, and diluted household bleach is another option. Always test a small area first and follow the product instructions.

If you're oiling tannin-rich timber yourself, give it a good clean with Grey Deck Cleaner first, otherwise the oil can soak in unevenly and look patchy.

NEED ADVICE?

Give us a call on 0450 404 639 or email sales@adelaidetimbercladding.com.au and we'll talk you through it.