§ Chapter 5 IRC 2021
Floors
10 entries from Chapter 5 of IRC 2021, organized by section number. Each entry covers what the code requires, why it exists, what inspectors look for, and common mistakes.
§ 01 Sections
All 10 entries.
Sorted by section number. Click any row for the full entry — answer, requirements, edition diff, related sections.
Section
Title
Question
R317.1
Wood in Contact With Concrete Often Needs Decay-Resistant or Treated Material
R317.1
When does wood touching concrete need to be pressure-treated?
When does wood touching concrete need to be pressure-treated?
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R502.3
Floor Joist Spans Depend on Size, Species, Spacing, and Load
R502.3
How far can floor joists span under the 2021 IRC?
How far can floor joists span under the 2021 IRC?
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R502.3.3
Floor Cantilevers Are Limited by Joist Size, Backspan, Load, and Bracing
R502.3.3
How far can floor joists cantilever past a beam or foundation?
How far can floor joists cantilever past a beam or foundation?
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R502.5
Floor Girders and Beams Must Be Sized for Tributary Load and Span
R502.5
How big does a girder or beam need to be under a floor?
How big does a girder or beam need to be under a floor?
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R502.6
Floor Joists, Beams, and Girders Need Minimum Bearing or Approved Hangers
R502.6
How much bearing do floor joists, beams, or girders need on wood, steel, masonry, or concrete?
How much bearing do floor joists, beams, or girders need on wood, steel, masonry, or concrete?
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R502.7
Floor Joists Need Restraint Against Rotation at Supports
R502.7
Do floor joists need blocking or bridging at supports?
Do floor joists need blocking or bridging at supports?
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R502.8
Floor Joist Holes and Notches Have Strict IRC Limits
R502.8
Can I notch or drill holes in floor joists for plumbing or wiring?
Can I notch or drill holes in floor joists for plumbing or wiring?
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R503.1
Floor Sheathing Thickness Must Match Joist Spacing and Panel Rating
R503.1
What thickness subfloor is required for floor joists spaced 16 or 24 inches on center?
What thickness subfloor is required for floor joists spaced 16 or 24 inches on center?
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R507.5
Deck Beams Must Bear on Posts or Approved Connectors
R507.5
What does the 2021 IRC require for deck beam bearing on posts?
What does the 2021 IRC require for deck beam bearing on posts?
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R507.9
Deck Joist Spans Must Follow R507 Tables and Deck Loading
R507.9
How far can deck joists span under the 2021 IRC?
How far can deck joists span under the 2021 IRC?
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