Understanding IRC Deck Beam Span Charts
The International Residential Code (IRC) provides crucial guidelines for residential construction, including the design and sizing of deck beams. One of the most useful tools in this context is the IRC deck beam span chart. This chart simplifies the process of determining the appropriate beam size based on the span and spacing of the joists. Let's delve into the intricacies of IRC deck beam span charts, their importance, and how to use them.
Why Use IRC Deck Beam Span Charts?
IRC deck beam span charts are invaluable for several reasons. Firstly, they ensure compliance with building codes, preventing potential issues during inspections. Secondly, they promote safety by providing guidelines for structural integrity. Lastly, they save time and effort by offering a straightforward method to determine beam sizes, eliminating the need for complex calculations.
Understanding the IRC Deck Beam Span Chart
The IRC deck beam span chart is a table that outlines the maximum allowable spans for deck beams based on the spacing of the joists they support. The chart considers the load that the beam will bear, including the weight of the decking material, any loads from snow or rain, and live loads (like people or furniture).

Key Factors in the Chart
- Beam Span: The distance between supports, typically measured in feet.
- Joist Spacing: The distance between adjacent joists, usually expressed in inches.
- Beam Size: The dimensions of the beam, typically given in inches.
How to Use the IRC Deck Beam Span Chart
Using the chart is straightforward. First, determine the span of your deck beam. Then, find the corresponding joist spacing in the chart. The intersecting cell will provide the minimum beam size required to support the given span and spacing. Here's a simple example:
| Beam Span (ft) | Joist Spacing (in) | Beam Size (in) |
|---|---|---|
| 8 | 12 | 2x8 |
In this example, for a beam span of 8 feet with 12-inch joist spacing, you would need a 2x8 beam.
Factors Affecting Beam Size
While the chart provides a starting point, several factors can influence the beam size. These include the type of decking material, the load the deck will bear, and any additional loads like snow or rain. Always consult with a structural engineer for complex or unique projects.

Conclusion
IRC deck beam span charts are powerful tools that simplify the process of determining beam sizes for residential decks. They promote safety, ensure compliance with building codes, and save time and effort. Understanding and using these charts is a crucial step in designing and building safe, durable decks.
More Details
FIGURE 6-18 Typical deck joist span and supports. TABLE 6-5 Deck beam spans (feet - inches). Species. Size. Deck joist span (ft.) 8. 10. 12. 14. 16. Southern ...

Maximum allowable spans for wood deck joists, as shown in Figure R507.6, shall be in accor- dance with Table R507.6. The maximum joist spacing shall be limited ...

In this ar- ticle, I'll focus on how to read the new maximum deck beam span tables in the. 2021 IRC, and explain how to use the code's new “joist span factors” ...

Maximum allowable spans for wood deck beams, as shown in Figure R507.5, shall be in accordance with Table R507.5. Beam plies shall be fastened with two rows of ...

NOTE: R507.5 Beam plies shall be fastened with two rows of 10d nails 16” OC along each edge. Deck Beam Span Chart.

International Residential Code (IRC). BEAM. BEAM. POST. POST. TABLE R507.6. DECK BEAM SPAN LENGTHSa, b (ft. - in.) SPECIESc. SIZEd. DECK JOIST SPAN LESS THAN OR ...

02.02.2018 ... On multiple spans the end beams pick up 1/2 of the load for the span and the mid span beams pick up the entire span load. Using ...

Beam size is based on IRC; Table R507.5, for a 40 psf live load, utilizing ... Deck Joist Span Less Than or Equal to (feet):. Page 5. DECK JOISTS. Maximum ...

03.01.2005 ... Size your deck beams and headers with our easy-to-use span table, which allows you to cross reference the post spacing and joist length to ...

5, shall be in accordance with. Table R507.5. Deck joists shall be permitted to cantilever not greater than one-fourth of the actual, adjacent joist span. R507 ...

Beam Span. Page 8. 8. PRESCRIPTIVE RESIDENTIAL WOOD DECK CONSTRUCTION GUIDE. American Wood Council ... Wood Deck Construction Guide. DCA 6 – 2012 IRC Version.

08.05.2024 ... I walk through how to determine the maximum span for beams between posts for a deck to make sure that you are IRC compliant.

29.01.2025 ... This table tells you the proper beam size based on how far your deck joists span and what type of lumber you're using.

ICC Digital Codes is the largest provider of model codes, custom codes and standards used worldwide to construct safe, sustainable, affordable and resilient ...

Span charts for deck joists and beams in a variety of framing materials, including wood and steel.

13.09.2022 ... 2018 International Residential Code, Country Club Hill, Ill. Table R507.5 Deck Beam Span Lengths. 39. Source: International Code Council (ICC) ...

TABLE R507.5. DECK BEAM SPAN LENGTHSa, b, g (ft. - in.) SPECIESc. SIZEd. DECK JOIST SPAN LESS ...

22.05.2025 ... *All construction shall be in accordance with 2021 IRC Section 507; Decks ... TABLE 3: Deck Beam Span Lengths a,b (ft. - in.) May 22, 2025. Page 7 ...

... deck, have a look at this guide.) IRC Table R50706 Deck Beam Span Lengths. The beam spans are based on the span of the deck joists, which are listed in 2 ft.

28.03.2021 ... The most important thing to know about this beam span table is it assumes every joist is cantilevered beyond the beam by 1/4 the span. All that ...
