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A post about posts (or a column about columns)

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Sometimes, you just have to say the same thing over and over. And we're going to do it again. (As one of our building inspectors says, "I love, admire and respect redundancy.")

Last week, we discovered a brand new deck built with (alas) 4x4 posts... now, any readers of these writings can probably guess what happened next.

The builder was instructed to remove those posts, and replace them with 5 1/2 square (known as 6x6) posts. This isn’t something we like to do at all. In fact, we dread having to tell someone they just built something that doesn’t meet Code, which is why we have posts like this on our website and social media feeds.

The picture here is a perfect example of a deck post done right: note the post is secured by a bracket set into the concrete.

Here’s the super-simple summary: decks attached to a building require nominal 6x6 posts supported by foundations (sonotubes, helical screw piles, frost wall).

Where can you use 4x4 posts on something attached to a building? For carports (not awnings over a deck) and fire escapes (not exit stairs! Questions? Call our office). That’s it.

The other worry we have: deck blocks. Please, please, do not use deck blocks for any structure attached to a deck: this leads to risk of structural weakness due to frost heaves. The only place you can use these is on small accessory structures (and this includes things like a small set of stairs NOT attached to a building.)

Since the Codes are now available online, we’ll cite the section of Code regarding posts, which are technically called columns:

Since the Codes are now available online, we’ll cite the section of Code regarding posts, which are technically called columns:

9.17.4.1. Column Sizes
1) The width or diameter of a wood column shall be not less than the width of the supported member.
2) Except as provided in Article 9.35.4.2., columns shall be not less than 184 mm for round columns and 140 mm by 140 mm (that’s 5 1/2 inches) for rectangular columns, unless calculations are provided to show that lesser sizes are adequate.

BTW: “unless calculations are provided” means “show us an engineer’s approval that this is good enough.” Without going into details, let’s just say that obtaining an engineer’s approval will cost a whole lot more than just using the right-size post the first time.