FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Plus Icon Close Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Main Menu
Subscribe

In every issue you'll find...

  • Expert insights on techniques and principles
  • Unbiased tool reviews
  • Step-by-step details to master the job
  • Field-tested advice and know-how
Subscribe Now!
Subscribe
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
  • Join
  • Log In
Main Menu Subscribe

Fine Homebuilding Project Guides

Decks

Guide Home
Chapter
  • Design & Planning
  • Tools & Materials
  • Footings & Foundations
  • Framing a Deck
  • Installing Decking
  • Installing Railings
  • Deck Stairs
  • Custom Details
  • Finishes and Maintenance
  • Complete Deck Builds
How-To

Complete Guide to Sizing Deck Footings

Use the charts and tables in this comprehensive guide to choose the right size beams and specify the appropriate concrete footings for your next deck project.

By Mike Guertin Issue 245 - Aug/Sept 2014
Article Image

Synopsis: Mike Guertin takes the guesswork out of deck loads in “Sizing Deck Footings.” With plenty of guides for determining beam configurations and footing size, style, load, and frequency, Guertin addresses the central concerns determining safe and accurate support.

Footings transfer the weight of a deck and its occupants to the ground. How many footings you need and how big to make them is specific to each deck. Doing the calculations takes only a few minutes, ensures that I’m following best building practices, and keeps me from digging more than necessary.

The size and spacing of footings tie directly to the maximum spacing between posts of the beam they support. A larger beam can span a greater distance, requiring fewer but larger footings. The American Wood Council publishes the Prescriptive Residential Wood Deck Construction Guide, which is based on the International Residential Code (IRC). Commonly referred to as DCA-6 (awc.org/Publications/DCA/ DCA6/DCA6-09.pdf), it contains tables for sizing deck beams. The DCA-6 assumes a 40-lb.-per-sq.-ft. (psf) live load and a 10-psf dead load. (Live load is the weight of occupants and furniture, while dead load is the weight of the structure.) Although the DCA-6 tables are valid in most jurisdictions, snow loads (found in the IRC) in northern New England or the Western mountains may exceed 40 psf, and you’ll need to substitute that for the live load. Some local building codes may also require designing to a greater live load. In either case, you may then require an engineer’s help.

Knowing the total load in psf, the size of the deck, and the number of footings, I can calculate what each footing has to support. The footing size is based on this load and the bearing capacity of the soil.

Choose a beam

Several factors determine which beam setup to use. Should it overhang the end posts or end flush with them? Is there a backhoe at hand so that digging a few large footings makes sense? Or is this deck on a house with established landscaping that calls for a greater number of smaller-diameter footings that can be dug by hand around obstructions? What is the joist span?

After answering those questions, I choose a beam configuration, such as a double 2×8, from the DCA-6 table and determine the number of footings needed based on the size of the deck. I prefer a double 2x beam because it can rest on notched 6×6 posts. The 2 1⁄2-in.-thick leg on the back of the notch bolts to the beam. Triple 2x beams sometimes make sense, but they require a structural connector to join to the post.

how to choose right size beams and footings for deck
This illustration shows some common ways to configure deck beams; view the PDF below to get more detailed information about acceptable deck beam and footing sizes.

The DCA-6 table allows joist overhangs (cantilevers) past the beam of up to one-quarter of the span between the beam and the ledger. The beams themselves can overhang the end posts by one-quarter of the post spacing. By cantilevering the end of the beam, you often can eliminate one footing.

 

For more photos, drawings, and details, click the View PDF button below:

 

 

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Sign Up
View PDF
X
X
Previous: Helical-Pile Deck Footings Next: How to Calculate Deck Footing Size

Guide

Decks

Chapter

Footings & Foundations

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Decks

Decks

Hundreds of articles and videos by top deck-building pros on how to design and build a beautiful, sturdy, and safe deck

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Decks Project Guide.

Start Free Trial

Design & Planning
  • Basic Design Options
  • Generating Plans
  • Calculating Deck Loads
  • Code Compliance
Tools & Materials
  • Deck Building Tools
  • Foundation and Framing Materials
  • Decking Materials
  • Fasteners and Hardware
Footings & Foundations
  • Choosing a Foundation
  • Sizing and Laying Out Footings
  • Excavation
  • Pouring the Foundation
Framing a Deck
  • Framing Overview
  • Installing the Ledger
  • Setting Posts and Beams
  • Installing Joists
Installing Decking
  • Decking Basics
  • Installation Process
  • Adding Fascia and Other Decorative Elements
Installing Railings
  • Installing Deck Railing Posts
  • Building Wood Rails and Balustrades
  • Non-Wood Railing Options
  • Installing Nonwood Balustrades
Deck Stairs
  • Deck Stairs Overview
  • Laying Out, Cutting, and Installing the Stringers
  • Installing Treads, Risers, and Stair Railings
Custom Details
  • Benches, Planters, and Privacy Features
  • Pergolas
  • Lighting
Finishes and Maintenance
  • Deck Finishes
  • Cleaning and Refinishing
  • Inspection and Repair
Complete Deck Builds
  • Grade-Level Decks
  • Raised Decks

Fine Homebuilding

Follow

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Manage Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Privacy Policy
  • Careers
  • Copyright
  • Terms of Use
  • Accessibility
  • CA Privacy Rights

© 2021 The Taunton Press, Inc. All rights reserved.

    Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House
  • Podcasts

  • FHB Podcast
  • ProTalk
  • Account

  • Log In
  • Join

    Podcasts

  • FHB Podcast
  • ProTalk
  • Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

    Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

    All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

    Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

    More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • Customer Support

    Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Follow

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 52%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in