since your in ca, and your winters are mild unless your in the mountains , you really don't need to go deep. 2' is probably sufficent. amount of concrete is determined by the size of your post. here in the north east we typically have 4x4 pt posts sitting in 8 to 10 holes up to 4' deep. set the post, then fill with concrete.
how deep is the frost line? if your setting deck posts move up in the spring then settle back down as the weather warms, then you have a bad case of frost heave-osis. so how deep is the frost line? in the winter, the ground freezes from the top of the soil downward. the depth of frost
and this is, when building a deck, how deep do you dig the post holes? well, i'm going to start off by explaining a frost-thaw cycle. what happens is, the ground contains moisture, when it freezes
up vote 2 down vote favorite. i am building a deck. how about setting 6x6 p.t. posts down on a concrete footing at 4 feet deep the frost line here and fill with gravel and soil, and then let the posts run high for the railings? this is instead of doing concrete piers and setting posts on them above ground.
one is to put 12x4 round footers at the bottom of a 42' hole and set the post on that and bury it. some will put the post on the soil, hammer a few nails in the side of the post and pour cement around it. the requirement to bury 42' below grade is because of the frost that would heave the posts and deck if it were on top of grade.
how deep to dig in posts. dig posts or footings to local code requirements or at least six inches below the frost line. always backfill under posts or footings with gravel for proper drainage. in warmer climates you can use premade footings. check with your local code enforcement agency for specifics. wood vs. steel and other footing options
in the past, many decks were built with 4x4 support posts also called structural posts . but these can bow seriously, even if a deck is only 3 feet off the ground. for that reason, we strongly recommend that you use 6x6s instead, even if your building department does not demand them. and if a deck is over 10 feet tall, you should install bracing.
if you have time, start the holes one day, fill them with water and come back to remove the much softened soil the next day. measure and mark the location of each fence post. post hole diggers have a maximum effective depth of about 3/4 of their handle length, so a five foot pair will dig about 3 1/2 half deep.
the deck post must be connected to a concrete pier if possible using metal connectors and fasteners. how much do decks weigh? the average deck can weigh several tons or over 4,000 pounds.
it's just about impossible to dig deep deck construction post holes without a clamshell digger - maybe i have just forgotten what life was like without one. this tool is basically like two shovels facing each other and connected together, it's easy to work by digging the blades in and then seperating the handles to bring the shovel heads together.
depth considerations. if your post is 6-feet tall, you will dig down at least 2 feet. for the width, you need to make the hole three times the width of the post you intend to use. you need to dig a 12-inch wide hole for a 4-foot wood post. gates require a hole with a depth of 36 to 40 inches in the ground and with a diameter of at least 12 inches.
the deck posts connect to the concrete piers using similar metal connection post bases. there are several types of metal post bases, but they all connect to the concrete pier and to the wood post. once again, youll size the metal post base to the wood post that youre using.