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Materials & Specificationsaka: PT lumberaka: treated woodaka: CCA lumberaka: ACQ lumber

Pressure Treated Lumber

In Plain English

Wood chemically treated to resist rot and insects, required where wood contacts the ground or moisture.

Definition

Pressure treated lumber is wood that has been impregnated with chemical preservatives under pressure to protect against decay, insects, and moisture. It is required by code for wood in contact with or near ground, concrete, or masonry. Modern preservative treatments use copper-based compounds (ACQ, CA) that are safer than older arsenic-based (CCA) treatments.

Why It Matters in Bidding

Code dictates where pressure treated lumber is mandatory—sill plates on concrete, ground-contact framing, and similar locations—so estimators must distinguish treated from untreated material in the takeoff to price each correctly. Treated stock carries a premium and uses corrosion-resistant fasteners and connectors, an easy-to-miss cost that adds up across a framing package. Specifying the wrong retention level or fasteners invites callbacks and rejected inspections that hurt margin.

Example

Taking off a deck and the building's mudsills, the estimator carries pressure treated lumber for the ground-contact posts and sill plates plus hot-dip galvanized hangers and fasteners, separating that line from the standard SPF used for the upper framing.

Related Terms

Dimensional LumberTreated LumberSoftwoodFastener

Frequently Asked Questions

Codes generally require treated wood wherever lumber contacts or sits near the ground, concrete, or masonry—sill and mudsill plates, posts in or near soil, and framing exposed to persistent moisture. Estimators should scan the drawings for these conditions during takeoff and price treated material separately, since it costs more than standard untreated framing lumber.
Modern copper-based preservatives like ACQ and CA are more corrosive to steel than older treatments, so codes and manufacturers call for hot-dip galvanized or stainless fasteners and connectors. Using standard fasteners leads to premature corrosion and connection failure. Estimators should add the upgraded hardware cost whenever treated lumber appears in the scope.
Treated lumber comes in retention levels matched to exposure. Above-ground material has lower preservative retention for elevated, well-drained uses, while ground-contact has higher retention for posts and members in or near soil. Specifying the correct level matters for both durability and cost, so estimators should match the retention to the application shown on the drawings.

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