I have done the calculations for footing size based on the tributary area, concrete volume and soil bearing capacity. I need a 14 x 14 inch footing.
I’d planned on using a plastic form with sonotube. The smallest Big Foot form is 20″ and they don’t seem to be available. There is a 22″ SquareFoot form available. The SquareFoot with flange is 23.5″ so even with a 24″ auger there is not much play for positioning.
I could auger a 12″ hole and try to bell out the bottom. But at 48″ depth not sure how well I could remove soil. or how well I could even bell it given the depth and diameter.
Could also auger oversize hole to pour footing, put tube in later, backfill and pour the pier but then it’s a cold joint. Doing it all at once seems sketchy.
Are there smaller forms I’m not finding in my search? Other advice?
Thank you.
ps Are the cheap penetrometers worth it? I f I had a little more bearing capacity I could just drill a 12″ hole and call it a day.
Replies
I cant speak to the penetrometers but I recently had a similar situation with the bigfoot forms. I had a 29.5" bell at the bottom of a 12" sonotube. I dug my holes wide enough to clear the 29.5" bell, then positioned the tube on top of it and secured it to the form with screws (make sure you cut off the excess rings if you are using the largest tube. I made wooden forms to keep the top of the tube braced so it wouldn't move and backfilled the hole with the tube and form in place. I was about 50" below ground. Of course when you are backfilling do not throw large stones at the form as it could break it. Poured my concrete with rebar bracing and that was it. Big foot has recommendations on the proper steps to use when backfilling a below grade application. Hope this helps.
You can use helical piles. Fast and easy. I got a quote for 4 piles about two years ago that was $200 each.
Good on you for doing the calculation instead of just winging it. Is any AHJ requiring that you have an actual formed footing that is larger than the pier diameter to prevent uplift? What state are you in?
Do you have rocky soil or sandy soil? If sandy soil, belling out one or two inches and taking it out with a post hole digger will be no big deal. If you have rocky soil it would be tough and I would not recommend it.
What type of equipment are you using to auger the hole?
If you auger oversize to 14", why even worry about installing a sonotube and backfilling around it? Just earthen-form and pour the entire pier at 14". I've always found that it is tough to compact that 2 inches around the sonotube. What usually happens is it doesn't get adequately compacted and your piers settle out of plumb.
Lastly, if whatever plan you choose introduces a cold joint between the footing and the pier, you can easily remedy this issue by putting upright pieces of rebar in the footing pour; such that they stick out vertically into the future location of the poured pier. The portion of these rebars that are embedded in the footing should be L-shaped, to help limit any chanced of uplift separating your foundation assembly at the cold joint.
@eust2023
Considered helicals. Only found one in my area. But he would only do it as part of the deck contract. They are, by all accounts quick, easy, and cheap. And come with a capacity certificate apparently.
@DemetriV- Thanks for detailed reply.
I'm in NE Ohio. No requirement for footing larger than pier that I'm aware of. I'll ask that specifically.
Generally the soil here is silt. I expect natural grade was built up some with basement excavation. I'd planned on renting a mini skidsteer which I believe I can use up to an 18 inch auger.
The only reason for the tube with spread footing is less concrete, I guess. Maybe less visual impact too.
"piers can go out of plum"
I'm glad you told me that.
"belling out a couple inches is relatively easy"
I see that now. With a 12" hole I think I can bell out 4". Use a bit of tube to bring pier above grade, earth form below, Two or three 1/2" rebar. inside.
As you may have guessed I am an amateur. Thank you for helping me think this thru.
I'm in central Connecticut so roughly the same longitude as you. I went 48" down with my 12" deck piers and did not bell-out the bottom for a spread footing. The town approved the design. Frost line here is 42" and the soil is rocky/granular sand.
Skid steer with auger is a great idea. Make sure you get a digging bar that has a tamper on one end to compact the bottom of the hole.
Your plan of using a small section of tube to make the exposed portion of the pier look better is an excellent idea. Nailing a tic-tac-toe frame around it (made out of 2x4's) will keep it in place and at the right elevation.
Everyone is an amateur until they're not. Fake it 'til you make it!
Deck footings are the structural elements that support the weight of a deck and transfer it to the ground. They are usually made of concrete and act as the base upon which the deck's posts or piers rest. Properly installed footings are crucial to ensuring the stability and safety of the deck.
Here are some key points to consider regarding deck footings:
Size and Depth: The size and depth of the footings depend on the size of the deck, the type of soil, local building codes, and the weight the deck needs to support. Larger decks or decks with heavier loads will require more substantial footings. Commonly, deck footings are 12 to 24 inches in diameter and extend below the frost line in colder climates to prevent frost heave.
Types of Footings: There are different types of footings used for decks: