Decks glossary

Joist - horizontal framing under the decking. Span is measured face of support to face of support and does not include overhang. Beam - the member the joists bear on, carried by posts. Rim joist - the continuous joist attached across the ends of the other joists; guard posts often attach to it, which is why it must be at least 2x8 nominal.

Ledger board - the framing member fastened to the house that supports the deck's inner edge. Minimum nominal 2x8, must be flashed with approved corrosion-resistant material, and siding must come off before it's installed. Flashing - corrosion-resistant metal of minimum 0.019 inch nominal thickness (or approved non-metallic material) that keeps water out of the ledger connection.

Cantilever / overhang - joist length extending past the beam. Maximum allowable overhang cannot exceed one quarter of the actual main span. Post footing - the concrete pad under a post, bearing on undisturbed soil at least 12 inches below grade or below the frost line, whichever is deeper. Load path - the chain from decking to joist to beam to post to footing to soil; a deck fails at the weakest link in that chain.

Guard - the barrier required where the walking surface is more than 30 inches above grade, minimum 36 inches high, openings no larger than will pass a 4-inch sphere. Baluster - the vertical infill members of a guard. Rise and run - stair geometry; maximum riser 7 3/4 inches, minimum tread 10 inches, with variation between them limited to 3/8 inch. Stringer - the sloped board carrying the treads; must be minimum 2x12, with cut stringers limited to a 6-foot span and solid stringers to 13 feet 3 inches. Hidden fastener - a clip system that secures decking through the board edge instead of the face. Pressure treated - lumber treated with an approved preservative; all field cuts must be treated with an approved preservative such as copper naphthenate.