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How to tell if wood is pressure-treated — and what to do with it

Green tint, incision marks, end tags, and where it was used: the four ways to spot pressure-treated lumber. Plus what to do with it — it can't go in a dumpster bag, and here's where it can go.

A treated post with incision marks next to bare lumber

Four ways to spot it

  1. Step 01: Green tint

    Fresh treated lumber has a green or olive cast from the copper-based preservative. It weathers to grey, but the tint usually stays visible on cut ends.

  2. Step 02: Incision marks

    Rows of small slits pressed into the surface so the preservative penetrates — common on thicker posts, beams, and landscape timbers.

  3. Step 03: End tags

    A stapled plastic tag or ink stamp on the end reading "Ground Contact", "ACQ", "CA", "MCA", or "Treated". No tag doesn’t mean untreated — check the other signs.

  4. Step 04: Where it was used

    Anything that touched soil or weather is usually treated: fence posts, deck framing and joists, sill plates, retaining walls, planter boxes, play structures.

The rule since 2021

The easiest way to spot treated wood is to look for incision marks in the lumber — rows of small slits pressed into the surface so the preservative penetrates. The wood is often identified by green or dark brown coloring and staple marks from the end tag.

Examples of treated wood waste include:

  • Fence posts
  • Sill plates
  • Landscape timbers
  • Pilings
  • Guardrails
  • Decking

Recycled wood waste is often used to produce wood chips that are marketed to fully permitted biomass facilities, where they are used to produce renewable energy. Treated wood is wood that has been treated with chemicals to protect and preserve it from insect attacks and fungal decay — and it cannot be accepted by biomass facilities.

Due to regulations in force since January 1, 2021, imposed by the Department of Toxic Substances Control, all treated wood waste is considered hazardous waste in California and must be recycled at special facilities. If the recycling facilities we use find treated wood in a bag, there is a $100 surcharge for the extra work of sorting it and disposing of it safely.

What to do with treated wood

California classifies all treated wood as hazardous waste. It goes to a licensed hazardous-waste facility or a designated treated-wood collection site — not a dumpster bag, and not the regular trash. Treated wood found in a Yellowsack is a $100 fine, because the whole load then has to be handled as hazardous.

Keep it separate from the start: stack it on its own, and check with your county’s household hazardous waste program for the nearest drop-off.

Bare wood goes in a Yellowsack

Untreated, unpainted lumber — nails and hinges fine — takes the clean-wood rate, one of our lowest, and recovers at 99.9%.

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