Several Factors Determine The Deck Post Size to Safely Support Your Deck

Deck post size is important. So build your deck the right way, from the ground and posts up.

That means that once you have the footings in place you need to install posts - which will support the beams - that in turn support the joists – that support the decking – and eventually you, your family and friends.

As you can see a lot is riding on the deck post size. But what size of post is right for your deck?

The Deck Post Size Table below will help you answer that question or learn more about loads for posts.

Understand Loads First

If you haven't already read the article on load capacity, read it now and then continue on here.

The dimensions in the following table are based on a total load of 50 psf for the particular species of wood. So it is irrelevant if you are building a deck designed to withstand 70 psf.

In that case you would have to refer to the building code or other engineering manuals usually found at your public library to determine incremental differences.

From our example, take the largest load area of 28 sf and refer to the chart to determine the maximum dimensions of post that you should use given the load area.

In other words, look at the wood species, post size and load area and you will see the maximum height of post you can safely use. In this example, 28 sf falls under the 36. If you chose to use cedar post, its maximum height would be 10 ft.

Load Area (sf) per Deck Post
Maximum Deck Post Height (ft)
Wood Species Size 36 48 60 72 84 96 108 120 132 144
W. cedar. Redwood 4x4 10 10 9 8 7 7 6 6 5 4
6x6 12 12 12 12 12 12 12
Hemlock 4x4 10 10 10 9 8 8 8 7 7 6
6x6 12 12 12 12 12 12 12 12 12 12
Douglas Fir, Pine 4x4 10 10 10 10 9 9 9 8 8 7
6x6 12 12 12 12 12 12 12 12 12 12

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