Deck Construction: Joist, Beam, & Floor Framing Spans & Tables

FRAMING TABLES, SPANS - Framing span tables for decks, porches, other common building floor structures
- Deck beam span table
- Deck joist span table
- Deck joist rule of thumb
- Deck & Porch Construction & Structural Fasteners
- Deck & Porch Post & Beam Connectors: steel post cap connectors, plywood post to beam cleats, other connectors
- Deck & Porch Railings, Code Requirements, Safety
- Deck framing tables, codes, specifications
DECK & PORCH CONSTRUCTION - home
DECK CONSTRUCTION BEST PRACTICES - separate article
DECK DESIGN & BUILD - article series home
FRAMING TRIANGLES & CALCULATIONS - separate article
STAIR RISE & RUN CALCULATIONS - separate article
Questions & Answers about allowable spans for deck, floor, or porch framing.
References

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Recommended or allowable joist & beam spans: this article explains typical spans for deck joists, deck beams, and deck flooring, giving both standard span tables and a quick "rule of thumb" that works pretty well. Our page top photo shows a hybrid deck structure that encompasses a boat. No fasteners were found securing the boat to the deck however. This article explains deck framing. Basic building framing information is found at FRAMING SIZE & Spacing, Age, Types. Also see Deck Nails, Screws, Hidden Fasteners and Deck & Porch Connections: Ledger Boards. And see Preservative-Treated Framing Lumber. See Rot-Resistant Deck Lumber & Flooring for a discussion of lumber and flooring alternatives to preservative-treated wood.

Deck Joist & Beam Sizing Tables & A Quick Rule of Thumb for Sizing Joists

As explained in Best Practices Guide to Residential Construction, Chapter Four, Best Construction Guide for Building Decks and Porches

Spans, sizes and spacings for deck joists and deck beams are shown in Table 4-7 and Table 4-8 (shown below in this article) as well as in most carpentry texts and framing guides. Here we give a rough "rule of thumb" that will provide a reasonable guess at allowable deck joist spans for most lumber species and grades:

A Quick & Easy Rule of Thumb for Estimating Allowable Deck Joist Spans

While it is by no means a substitute for a proper table of spans and sizes of framing lumber, home inspectors often use a quick and dirty "rule of thumb" to guess whether or not deck floor framing has been over-spanned when joists are spaced 16" on center.

[(Depth of the Framing Member) - 2 ] x 2 = rough deck joist span limit for Southern Yellow Pine.

Example:

If you see a deck framed with 2x8 pressure treated lumber (typically Southern Yellow Pine or SYP), spaced 16" o.c.,

(8" -2) x 2 = 12' = maximum allowable span for a generic "deck floor joist"

A look at an actual span table will show that depending on the wood species, the allowable spans for a 2x8 floor joists with 40 pound live load with deflection limit of span/360, ranges from 10'5" (Western red cedar) to 12'9"
(Doug fir-larch).

Table of Maximum Beam Spans for Exterior Decks

Table 4-7: Maximum Beam Spans in Feet for Exterior Decks (C) J Wiley, S Bliss

[Click any image or table to see an enlarged, more detailed version.]

Table of Maximum Joist Spans for Exterior Decks

Table 4-8: Maximum Beam Spans in Feet for Deck Joists (C) J Wiley, S Bliss

-- Adapted with permission from Best Practices Guide to Residential Construction.

Details about selecting the proper fasteners for constructing decks and porches and how they are installed can be read at Deck Nails, Screws, Hidden Fasteners.

Also see DECK COLLAPSE Case Study (collapse of a new code-approved deck) and DECK FLASHING LEAKS, ROT Case Study for an example of an older deck with rot and collapse due to improper construction and missing building flashing.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
Manual for the Inspection of Residential Wood Decks and Balconies, by Cheryl Anderson, Frank Woeste (Forest Products Society), & Joseph Loferski, October 2003, ISBN-13: 978-1892529343, $39.00 at Amazon.com or at the InspectAPediaBookstore
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