What happens when a joist has a notch or hole?

A notch or hole can weaken a joist if placed incorrectly. The allowed location and size depend on the joist type and the framing design.

Glossary

What Is a Joist?

A joist is a horizontal structural member that supports a deck surface, floor, or ceiling. Joists transfer weight to beams, ledgers, walls, or other supports. In deck construction, joists form the frame beneath the decking boards and must connect securely so the surface stays supported and properly aligned.

Local relevance: Snoqualmie’s wet winters make drainage and moisture control important around deck joists, supports, and connections.

Quick Facts About Joist

Key Takeaways About Joist

Joists run across a deck frame and support decking boards.
Spacing and connections affect the deck’s strength and surface alignment.
Joists are not the same as beams or deck boards.

How Joist Works

A person drills into a wooden frame while a monitor shows a joist diagram outdoors

A joist spans between supporting parts of a deck frame. Each joist carries the load above it and passes that load to a ledger, beam, or other support. The joist’s direction helps determine how decking boards will run across the frame.

Related glossary terms: Blocking, Deck Ledger, Framing.

Deck builders set joists in a consistent layout and secure them with approved framing connections. Blocking may be added between joists to reduce movement and support board ends. The frame must also account for drainage, edges, stairs, and openings. A deck ledger connects part of the frame to a building, while a beam supports joists from below.

Two men fasten a wooden beam with a power drill on a timber frame construction site

Expert Note

When we build a deck, we check each joist for straightness, sound connections, and proper bearing on its supports. We also review areas around stairs, rail posts, and openings because those locations can need extra framing.

Joist in Practice: A Real-World Example

For a raised deck, joists form the frame below the decking boards and rest on beams or other supports. The framing plan also accounts for the stair opening so the surrounding joists stay supported.