Possible Problems With Different Deck Footing Sizes
by Beginner Builder
I recently started building a backyard deck and need a little help. I set the perimeter support posts in a hole and poured concrete only around them. If I set the interior supporting posts in concrete with a concrete footing am I going to have any problems with the deck sinking around the perimeter?
This is an interesting question and one that should be explained as it builds on some of the basic principles of deck footings discussed in this introductory article.
The part of the deck that has to support the largest loads is usually the middle areas of the deck. This is not an absolute but depends on the size of the tributary zones that are created when you establish your beam positions and the number and area or size of each footing.
As a general rule you need more footings or larger footings in the center of the deck to properly distribute the load to the soil below.
In your case you have used posts that are set into concrete without any footings along the perimeter of the deck and you used footings in the inner area of your deck.
This actually is technically congruent with the way loads are increased in the center of the deck rather than near the perimeter. So you may well be ok.
Where you would likely encounter real risks is if you had reversed the configuration you just described. That is to say if you had smaller footings in the center of the deck and larger footings around the perimeter.
But in future keep in mind that footings are always a great idea particulary bell shaped footings if you are in frost prone areas as they resist uplift more so than a vertical cylindrical hole with post embedded in concrete.