How much concrete for 4’x4′ posts for 19’x12′ deck?
I live in ontario, and I know i need to put my posts 4′ deep to get below the frost line, but wondering if i should pour a footing for the posts to sit on, or do i use a sonotube and fill it with conrete? how wide should the tube be? how much concrete will i need? Any help is appreciated!!
Replies
Pour concrete in the bottom of the hole, up to where the bottom of the post will be. This provides a bearing for the post (equal to the diameter of the hole, which should be sized for the expected load) without surrounding the post with rot-inducing concrete.
How high is the deck? If it's only a couple feet above ground level 6 inches in the bottom of the hole might do. If it's 8 feet you'll need a new plan. I'd also suggest going to 6" x 6" post instead of 4" X 4". Not much more in cost but huge dividends in strength and longevity.
Not enough information. Need to know the spacing between the posts to figure the loading and the footing size. It's all in the Decks and Outdoor Projects issue on the newsstands now.