Deck Footings.

[You]

Very Sandy soil. Trex or similar. 14" deck board on house (with the mindset I can come off of it with 14"rs or any smaller size). Heavy deck. 20'x26' overall (minus a 6'x12' notch in one corner where a breakfast nook juts out).

what diameter sonotube? How deep of footings? How many? Start first row of footings how far off of house?

any help is greatly appreciated!!

 

[Sub_Elect]

I am not sure what you need for # of pillars to support, but i do know that you want the footings to be 1/3 as deep as the height.

 

[You]

thanks for the reply! the deck is only 2' off the ground, i'm guessing a min of 4' in the ground?

 

[PrairieGhost]

I always put footings below frost line. Sometimes my building is overkill, but thats like guys who think a magnum is to big for deer. Do it right the first time and you never have to redo it. I don't have that much energy. I overbuild maybe, but it's because I'm lazy and don't like doing things twice.

 

[SupressYourself]

You definitely want the footings below the frost line. Over here in the east, that's 54 inches. You don't want that thing to move. Other stuff... don't know.

 

[espringers]

i've never put them below the frost line. they make those concrete blocks that accept 4 X 4 deck posts for a reason and its not because they expect you to put them 4+ feet in the ground. no codes that i know of require deck posts to be below the frost line. think about that for a minute. if the frost line is 48 inches deep, that means you actually need the the bottom of the post to be at 72 inches and then concrete for the next 2 feet. putting every 4 X 4 deck post 72 inches into the ground is completely unnecessary and is overkill. we dig in the concrete blocks a few inches and that's it. never had a problem.

 

[You]

thanks for the replies. im thinking 5' sonotubes now and letting them be a few inches above ground

anybody know how far to have the first row of footings from the house?

 

[espringers]

one thing... if you do decide to bury them in the ground, you must get them below the frost line. burying them and having them above the frost line is way worse than not burying them at all.

 

[PrairieGhost]

It's best to have s fee inches above ground just to keep your posts fr rotting over many years. Like the old cliche "do you want a fast job ot do you want a good job. I have seen deck supports go in five yesrd and some that were put in 20 years ago and still very good.

 

[NDwalleyes]

thanks for the replies. im thinking 5' sonotubes now and letting them be a few inches above ground

anybody know how far to have the first row of footings from the house?

The answer to this depends on a couple things. First is length of overall span and second is width of joists (8" vs. 10" vs. 12"). Go to the City of Bismarck community development website, they have several nice documents you can download, including a chart that will help you in determining footing placement based on deck size and joist width.

 

[eyexer]

If it's attached to the house you need to have them 4' deep. And you'll need a permit if it's in a city that has a building dept. And they usually inspect the holes before you pour the concrete to ensure the depth. I'd use 8" sauno tubes. 12" is better. Leave them a few inches above the ground and then use the post anchors you can drop in as soon as you pour. This will keep the post off the concrete and give you a great anchor. But you need to have things set up so you can string line where the anchors go so you can do that right after you pour to get anchors lined up.

 

[guywhofishes]

http://www.structuretech1.com/2013/06/frost-heave-and-deck-footings/

 

[sl1000794]

i've never put them below the frost line. they make those concrete blocks that accept 4 X 4 deck posts for a reason and its not because they expect you to put them 4+ feet in the ground. no codes that i know of require deck posts to be below the frost line. think about that for a minute. if the frost line is 48 inches deep, that means you actually need the the bottom of the post to be at 72 inches and then concrete for the next 2 feet. putting every 4 X 4 deck post 72 inches into the ground is completely unnecessary and is overkill. we dig in the concrete blocks a few inches and that's it. never had a problem.

I'd go with what sprinters said. We live in a 25x30 foot summer cabin on Lake Metigoshe that was built in 1961 and is supported in concrete blocks. Blow out the water lines in the fall, put antifreeze in the traps and turn off the power. Fifty plus years later all the doors close, all the windows open, etc. Just like supporting a house trailer.

 

[espringers]

Whatever u do, dont just go to 48 inches. Footings may be better than none. But footings that aren't deep enough have the potential to be much worse than none.

 

[PrairieGhost]

At the very least remove the high organic soil because they naturally collapse as the organics decompose. I had to go down 10 inches before laying a brick patio 18 years ago. It has not moved 1/4 inch.

 

[Captain Ahab]

i've never put them below the frost line. they make those concrete blocks that accept 4 X 4 deck posts for a reason and its not because they expect you to put them 4+ feet in the ground. no codes that i know of require deck posts to be below the frost line. think about that for a minute. if the frost line is 48 inches deep, that means you actually need the the bottom of the post to be at 72 inches and then concrete for the next 2 feet. putting every 4 X 4 deck post 72 inches into the ground is completely unnecessary and is overkill. we dig in the concrete blocks a few inches and that's it. never had a problem.

That is what I would do as well. Very easy to adjust if you are not perfectly centered too.

 

[deleted_account]

If it's attached to the house you need to have them 4' deep. And you'll need a permit if it's in a city that has a building dept. And they usually inspect the holes before you pour the concrete to ensure the depth. I'd use 8" sauno tubes. 12" is better. Leave them a few inches above the ground and then use the post anchors you can drop in as soon as you pour. This will keep the post off the concrete and give you a great anchor. But you need to have things set up so you can string line where the anchors go so you can do that right after you pour to get anchors lined up.

This