Rot-Resistant Wood: Species Ranked by Decay Resistance

Which woods resist rot? The US Forest Products Laboratory groups the heartwood of common woods into four classes, from very resistant to nonresistant, based on service records and laboratory tests (Wood Handbook Table 14-1). The short version: very resistant woods such as black locust, ipe, greenheart and jarrah can be used in contact with the ground; resistant woods such as the cedars, old-growth redwood, white oak, black walnut and genuine mahogany are good above ground; everything else, including most framing lumber, needs a preservative treatment where it stays damp. And in every species the pale sapwood has little or no resistance, so a board is only as durable as the heartwood in it.

What each decay class means in use

Very resistant woods

Resistant woods

Moderately resistant woods

Old growth and young growth

Decay resistance comes from extractives the tree deposits in its heartwood, and fast-grown second-growth trees often deposit less. The Handbook rates several woods differently by origin:

• Baldcypress: resistant (old growth); moderately resistant (young growth)
• Eastern white pine: moderately resistant (old growth only); otherwise slightly or nonresistant
• Longleaf pine: moderately resistant (old growth only); otherwise slightly or nonresistant
• Slash pine: moderately resistant (old growth only); otherwise slightly or nonresistant
• Teak: very resistant (old growth); moderately resistant (young growth)

That is why young-growth redwood and plantation teak sold today usually last less well outdoors than the old-growth timber those woods earned their reputation on. Resistance also varies a great deal from tree to tree within the more resistant species, the Handbook notes, much more than it does among non-resistant woods.

Choosing wood by use

Pressure-treated lumber

For most outdoor building, preservative-treated lumber (usually southern pine, which takes treatment well) is the practical answer. Treated wood is sold by use category, the system of the American Wood Protection Association printed on the end tag: UC1 and UC2 for interior use, UC3A and UC3B for exterior wood above ground, UC4A, UC4B and UC4C for ground contact from general to extreme duty, and UC5 for salt water. Buy wood labelled for ground contact (UC4A or higher) for posts and anything buried or set in concrete; AWPA guidance also calls for ground-contact wood close to the ground and in other places where it cannot dry, so above-ground wood is only for parts that drain and dry. Since the end of 2003, wood treated with chromated copper arsenate (CCA) has not been made for residential uses such as decks and play equipment in the US; current residential treatments are copper-based or other non-arsenical preservatives.

• Treat cut ends and drilled holes in treated lumber with a brush-on preservative: the treatment does not always reach the centre of the piece.
• Use fasteners and connectors rated for treated wood (hot-dip galvanized or stainless steel); copper-based treatments corrode plain steel.
• Design for drying: slope horizontal surfaces, keep end grain off the ground and leave gaps between boards. Wood that dries out rarely rots.

Frequently asked questions

What is the most rot-resistant wood?

Among woods in the Wood Handbook’s “very resistant” group: black locust (the only North American one in that group in our data), and imported ipe, greenheart, jarrah, lignum vitae, purpleheart, goncalo alves, angelique and azobe.

Is cedar rot resistant?

The heartwood of western redcedar, northern white-cedar, eastern redcedar, incense cedar, Port-Orford cedar, Alaska yellow-cedar and Atlantic white cedar is rated resistant: good above ground, not for burying. Cedar sapwood is not resistant.

Is pressure-treated wood better than cedar?

For posts and anything in the ground, yes: treated lumber labelled for ground contact outlasts untreated cedar. Above ground, cedar heartwood and treated lumber both do well if the wood can dry out.

Is oak rot resistant?

White oak heartwood is rated resistant; northern and southern red oak heartwood is rated slightly or nonresistant (Wood Handbook Table 14-1).

What wood is best for raised garden beds?

Resistant heartwood such as cedar, redwood or white oak, or lumber treated for ground contact. Avoid untreated pine, spruce and fir, which are not rot resistant.

Sources

1. USDA Forest Products Laboratory, Wood Handbook FPL-GTR-190 (2010): Table 14-1 (heartwood decay resistance), chapter 14 (use of resistant heartwood, variability, sapwood), chapter 15 (preservative treatment and use categories). A US Government work.
2. American Wood Protection Association use category system (UC1 to UC5), names as printed on treated-lumber end tags.
3. US Environmental Protection Agency: voluntary cancellation of CCA for most residential uses, effective December 31, 2003.

Last reviewed: 25 October 2026. Related: wood species database (sort by decay class), cedar vs redwood, ipe vs teak, fence post depth guide. Spotted an error? Please let us know.