Decks/Deck Footers


My deck is old and recently I noticed that some footers are rotted at the ground level, and have to replace most of them since the deck started to sink in some spots. The posts used are 6x6 embedded in concrete at ground level. This may have been the code 25 years ago, but I want to do it the right way. I have two questions; 1) the deck is 5 ft high on one side and 3 feet on the opposite side. It is my understanding that 4x4 posts could have been used but I would like to use the same 6x6, and the question is can I use a 12" footer (sonotube) and pour concrete to below the freezing line which is 30" for where I live? or do I have to use a 16" dia footers or 14x14. The reason I ask is the space where the footers are currently may not allow for 16" dia (or a 14"x14" square). Maybe I can use a 12" dia and at the bottom of the hole where the concrete will be poured the last 6-12" depth I can flare the hole out to 16", but the top will be 12". The second question is 2) that in one spot I have two 6x6 footers side by side. One supporting one section of the deck and the other another. What would be the proper size footer to support both of these posts. To prevent the same rotting I am going to place all of my posts above ground level using the J anchoring system, this way the posts will not be in standing water. Any suggestions, opinions or other ways of completing this project will be greatly appreciated especially anything with less concrete. Thank you advance foe the assistance.

example of footers
example of footers  
Hello, I think that the 12" sonotube should be adequate. Using the anchors to attach the posts to the concrete is a good idea. Almost all footers need to be roughly 16 x16 however a tube will do, the main concern with footers is that they extend down to undisturbed earth, meaning hard ground. Maybe you can explore a way to use only one support where the two are close by utilizing a small beam or either a larger support, either way if your footer has about 8" of concrete on every side of the posts you should be ok, it is more how deep you go to solid ground than the actual size of the footer. I would extend them about 3-4" above the ground also. Hope this helped.


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Eugene Clayton


I would be happy to answer any question reguarding the construction of decks, composites verses natural materials, structure support systems,railing applications,stair design, how to figure stairs etc.. Pretty much anything that has to do with decks and or porches.


I have been in the construction industry for over 27 years including new home construction, custom deck and screen porches. Most of my expertise is from framing custom homes for over 20 years. I now own and opperate a very successful custom deck and screen porch company in Atlanta Ga.

High school graduate

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