Building A Deck
Deck building detail pages:
Framing Lumber - Beams, Bracing & Joists
Framing lumber is used for the deck's supporting structure. Beams, bracing and joists work together to provide a solid, stable deck platform that safely supports vertical loads and resists lateral (side-to-side) forces. See the Prescriptive Residential Wood Deck Construction Guide for general requirements, beam sizes and assembly details, beam span types and spans, joist sizes and spans including maximum overhang lengths, and diagonal bracing requirements. Joist spans are limited to a maximum of 18 feet. Bracing is required for any deck two feet or higher above grade. Beams are generally assembled with multiple 2x members, but may also be solid-sawn heavy dimension or timbers, glued-laminated timber or structural composite lumber.
Framing Lumber
|
Selection |
Beams |
No. 2 (2)2x6, (2)2x8, (2)2x10, (2)2x12 |
Beams |
No. 1 (3)2x6, (3)2x8, (3)2x10, (3)2x12
Glued-laminated timber or structural composite lumber to size. |
|
Bracing |
No. 2 2x4, 2x6 |
Bracing |
No. 1 2x4, 2x6 |
|
Joists |
No. 2 2x6, 2x8, 2x10, 2x12 |
Joists |
No. 1 2x8, 2x10, 2x12 |
|
Installation |
Space joists 24" on center maximum
Space joists 16" on center maximum if decking is diagonal |
Space joists 16" on center maximum
Space joists 16" on center maximum
if decking is diagonal
To improve fastener grip, double joists
where deck boards abut.
|
|
Durability |
Pressure treated for Above Ground Use |
Pressure treated for Above Ground Use |
|
Improper boring or notching can significantly weaken joists. See illustration for notching and boring limits. If a joist is bowed, install it with the crown up. Gravity and the weight of people and furniture will flatten it.
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