depth for deck pillars?

[R_Ethug]

so i'm building my deck.. rented an auger tonight and went at it for my holes

i need 6 done.. 4 of them are almost 3 feet down and well into the clay
1 is 2' down and the clay is so tough i can't get past it with the auger
the 6th is only 1.75' down but is ontop of a rock that is wayyy bigger than the 8" hole

i'm going to try and hand dig after this and see how far i get them from that

but really there is no freaking way in hell i can go down 4 feet.. when we did our fence i think most post holes were 2-3 max! as airdrie is solid freaking rocks and clay under the builders top soil so its extremely hard ground

thoughts?

[Remedys]

Re: depth for deck pillars?

The depth depends on how tall the deck is going to be, if the deck was going to be 4 feet tall, then 2-3 feet deep is more than enough. I am not even going auger holes for mine, just use above ground mounts.

[Stonewall]

Re: depth for deck pillars?

How big of sonotubes are you using (if any)? How big are your posts? How high is your deck off the ground? Are you cementing the deck right into the ground or cementing in those braces on the ground and screwing into those?
City of calgary sais the following:
• A minimum depth of 1.2 m (4’-0”) below grade is
required for a foundation system.

Really all of this should have been discussed when you drew out your plans and got your permit. They are really helpful with homeowners I have found (well at least in Calgary).

Some more quick links I found for you:
http://www.hometime.com/Howto/projects/decks/deck_7.htm
http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf

[R_Ethug]

Re: depth for deck pillars?

brent deck height is max like 30" one corner and like 26" the other corner (thats to the top of the actual decking)

posts are going to go into post saddles that i'll set and level into the concrete once i get there

concrete is going into 8" sonotubes that i'll cut to length.. i may leave 1-2" sticking out of the ground too as you never know if the thing may sink down but i highly doubt it would

[Stonewall]

Re: depth for deck pillars?

Sounds like you are all good then, with saddles I don't think they need to be super deep but below the frost line would be a good idea to avoid shifting.

[R_Ethug]

Re: depth for deck pillars?

yea those saddles are funny HUGE like 8 or 10" rebar on the bottom you poke in.. then i'll level them and push them down a bit to sit in the concrete.. then i need to use my string layout and more strings to line them all up perfectly square or those beams will be sitting funny hahahah

one thing i love about totem and my deck size.. all the boards are the right size.. the only cutting i have to do is the posts and then midway blocking 2x8 into chunks between joists.. easy stuff

[Stonewall]

Re: depth for deck pillars?

So what did you decide for deck surface?

[R_Ethug]

Re: depth for deck pillars?

5/4x5 pressure treated rounded edged... good enough for me

[Al]

Re: depth for deck pillars?

you should make sure that it is 4' deep and also that it has a bigfoot at the bottom of the sono tube. You don't want to regret it when your deck starts lifting in the spring. I brought in a mini hoe to dig my holes and it cost me $70. Much easier than digging or augering.

[R_Ethug]

Re: depth for deck pillars?

yea i'll dig the sides out so it makes a foot at the bottom i'm not worried

al come see how hard the earth here is..

one hole last night the auger was just spinning in the clay.. i'd hose it down but it would just spin.. looked like polished concrete when i removed it.. the earth here is hard as hell.. plus the yard is settled now so i'm not too worried

[darkmanCANADA]

Re: depth for deck pillars?

My deck is 13'x26' and 36" off the ground. I used 5 piles that were between 4' and 5' deep with 8" Sonotubes. Overkill but it ain't moving. Oh yeah, no hand digging here. Used a guy with a Bobcat with a 12" auger.

BTW the guys at Totem told me I could get away with 3 piles 3' to 4' deep and 6" Sonotubes.

[Ur0Drivr]

Re: depth for deck pillars?

Yeah, the 4' frost coverage line is something that you should get below.

Here are a couple of general details for what happens normally at the deck foundation. The footings would, as a general rule, be 30"x30"x8".

[cdnalpina]

Re: depth for deck pillars?

I have a deck and fence construction company and I have seen the effects first hand of people not putting the piles down deep enough (warped decks, posts listing sideways BADLY). Not getting them below the frost line means that they will heave and sink with the frost. The bigger your deck, the more pronounced this gets. I appreciate this is a huge pain but trust me, it will be worth the extra diligence to get them down there.

When you encounter tough clay, pour some water in the hole and let it sit for a bit and then pick at it with a prybar.shovel/etc. The water will soften up the clay and you will be able to bite into it much more easily with the auger/shovel. Where I live the ground is glacial till so it is clay and big rocks throughout. It took me a day to dig two holes but now it is peace of mind that the posts will be solid and secure.

What I usually do for customer's decks is get a bobcat guy in. My time versus the cost of a bobcat guy is a no brainer. They can knock those off in about 20 minutes.

When you go to do the piles, use Sauno tube for sure. They come in 8' lengths - just cut them in half with a saw and put them in the hole. Back fill and true them up at the same time and you will be set. I'd go 8" diameter.

[Ur0Drivr]

Re: depth for deck pillars?

^^Listen to the man.

[Al]

Re: depth for deck pillars?

It will be cheaper in the long run, it doesn't matter how hard the ground is, it still moves.