Deck Post Footings Size

A larger beam can span a greater distance requiring fewer but larger footings.

Deck post footings size.

Post spacing should be even. Step 2 dig footing holes about 6 inches deeper than required. The american wood council publishes the prescriptive residential wood deck construction guide which is based on the international residential code irc. Use added batter boards and string to mark rows of posts.

This is between 3 and 14 in concrete. In this case though i couldn t find a current source with a table that shows allowable tributary areas for various sizes and wood species of posts. Unless the deck requires engineering i refer to a beam span table as i design the framing. For aesthetic reasons most deck builders size them all based on the worst case loading.

Step 3 fill the bottom of the hole with 6 inches of gravel and compact the gravel with a 2x4 or wood post. In order to determine the proper size for your footings you will need to establish how much total weight they are going to have to support and what kind of soil they are covering. This is a permanent footing and is great for large or high decks that need very strong footings. To calculate the load you should use 40lbs per square foot for live loads these are variable loads that are dynamic such as the weight of.

Of course you can get a 24 base size and it will spread weight over an even greater surface area. The number of footings needed to support a deck beam is dictated by the beam s size. Depending on how heavy and high your deck is your concrete footing underground may take 1 4 bags of concrete. The size and spacing of footings tie directly to the maximum spacing between posts of the beam they support.

When the irc leaves us hanging we can often find an alternative rope to climb. The evolution compression post base will make any deck footing look fantastic because the connection mechanism is completely hidden deep. A good size for a common backyard deck is a 10 or 12 diameter for the sonotube and a 20 base diameter. Typical post size is a pressure treated 4 4.

My calculations came up with 15 3 4 in. Once you decide the distance measure from the house for the first row of boards. Deck footing size chart. There is little material cost to a buried post footing.

Footings typically must extend below the frost line to prevent shifting during freeze thaw cycles.