Deck Post Footings Size

Diameter center footing size and table b3 calls for a 16 in.

Deck post footings size.

Step 3 fill the bottom of the hole with 6 inches of gravel and compact the gravel with a 2x4 or wood post. This is between 3 and 14 in concrete. Footings typically must extend below the frost line to prevent shifting during freeze thaw cycles. 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. Unless the deck requires engineering i refer to a beam span table as i design the framing. 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. Deck footing size chart.

Typical post size is a pressure treated 4 4. The evolution compression post base will make any deck footing look fantastic because the connection mechanism is completely hidden deep. 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. 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.

Use added batter boards and string to mark rows of posts. A larger beam can span a greater distance requiring fewer but larger footings. Post spacing should be even. The american wood council publishes the prescriptive residential wood deck construction guide which is based on the international residential code irc.

Step 2 dig footing holes about 6 inches deeper than required. My calculations came up with 15 3 4 in. A good size for a common backyard deck is a 10 or 12 diameter for the sonotube and a 20 base diameter. A comparison of the footing sizes i calculated for the example deck resting on 1500 psf soil in the sizing deck footings article and dca 6 table b3 shows an almost identical result.

There is little material cost to a buried post footing. For aesthetic reasons most deck builders size them all based on the worst case loading. Of course you can get a 24 base size and it will spread weight over an even greater surface area. This is a permanent footing and is great for large or high decks that need very strong footings.

Post spacing is going to depend on your design local building codes the size and length of your beams and the size of your posts.