Deck Footings for Dummies

Details of deck footing design

Ever asked someone a question and received an answer that sort of left you scratching your head? If you're like some of our staffers at the Antisocial Network, you start to wonder what it is that didn't make sense about some of the seemingly sensible posts they run across. Take, for instance, a little thing called "How to Calculate Deck Footings"¹ that repeat offender James Wiley penned for eHow.com (now at Hunker.com): while the young Spanish-"global studies" graduate with a yen to write television scripts appeared to know what he was talking about, a little digging exposed his ignorance.

James started out by – as far as he and his content editor (probably a J-school grad who'd never even seen a footing) could manage – defining footings:

"Deck footings are vital to the construction of a deck as they establish a solid foundation for building the deck. Deck footings typically are driven underground and encased in cement to provide extra stability. It is therefore imperative to make proper deck footings calculations..."

At least he got the first sentence right... but then he went totally wonky with that "driven underground and encased in cement" bull. James, you fool, the footing is the cement! Wiley goes on to blather about deck design, informing his readers that "...most standard rectangular decks are built with two footings with the weight evenly distributed between them..." ...which might be a surprise for anyone building a free-standing deck! We think you want a footing at each support post, but what do we know? (It's a rhetorical question: we know more than Wiley). Anyhow, you're supposed to calculate the area of the deck and divide it by the number of footings in your design, then calculate the load per footing (ft² per footing * 55 lbs/ft² average load). Once that's done, James says that you

"Consult the deck footing sizing chart and match the total load with the surface the footing will be buried in... The chart will tell you how long to make your footings."

Ummm, no James, it won't tell you "how long," the chart will tell you the required diameter of a footing – its length is controlled by such factors as the depth to the frost line and the substrate. With that claim, Wiley revealed that he had no idea what he was talking about. That, reader, is the main reason we hand out the Dumbass of the Day award – in James' case, for the third time.

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was   ehow.com/how_5961953_calculate-deck-footings.html

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