ROC Decks · Glossary

deck building and repair glossary

Plain-English definitions for the technical terms you'll see in quotes, proposals, and inspection reports. Bookmark this when you're comparing bids.

PT (pressure-treated) lumber

Wood infused with copper-based preservatives. Resists rot + insects. Standard for deck framing.

UC4A rating

Use Category 4A — ground contact + freshwater. Required for posts that touch soil. Higher than UC3 (above ground).

Composite decking

Wood-plastic + capped polymer board. Low maintenance, 25-30 year lifespan. Trex, TimberTech, Azek brands.

Joist hanger

A metal bracket that connects joists to a beam or ledger. Code-required; nailed in place with structural fasteners.

Ledger board

The deck's attachment to the house. Must be lag-bolted (not nailed) into the rim joist with flashing above.

Flashing

Sheet metal that diverts water from the ledger-to-house junction. Critical to prevent rot in the rim joist.

Footings

Concrete piers below frost line that support posts. In Monroe County: 42 inches minimum depth.

Span tables

Code tables specifying max joist span by lumber species + size. Determines whether 16" or 12" on-center spacing is required.

Stair stringer

The diagonal board that supports stair treads. Code requires specific rise/run ratios + ≥36" width.

Railing height

Code requires 36" on residential decks 30"+ above grade. Balusters ≤4" apart.