You must be in a very northern climate if code requires 4' deep footings. I'm in northern Illinois and 42" are required.

The round tubes are excellent. Just be certain they are plumb and level. I use pea gravel to fill space around the exterior when the hole is larger. Concrete should not cure too quickly (mostly a chemical process, not evaporation) - absolutely do not pour your footing in sections. Keep something damp atop the pour for several days afterward. Burlap is a good thing to use and re-dampen daily for a week.

Here's how I built mine. I punished myself and excavated with a clamshell digger. I dug a 12" diameter hole for the footings about 48" deep, placing about 6" of gravel at the base for drainage. At the surface, I framed a 12" square. 3 or 4 sections of rebar are tied together at the bottom and allowed to spread toward the surface. After filling with concrete (all the way, one pour) a 1/2" x 8" "L" bolt was embedded into the wet concrete for later attachment of a stand-off post base. Because I poured footings before building the patio, I used a transit to make certain the top of all footings were level.

From a few of the linked photos you can sort of see the footings. I went with 12" for the proportional look with 8" posts. My concrete is entirely covered in the final build.

Hopefully this will give you an idea, but check local codes too.

Here is a link that might be useful: Pergola

Our local code requires 2 feet deep; we went with 3. Our deck + pergola required diameters ranging from 12" to 36", and we used the appropriate tubes for each. Loosened the dirt with a tractor auger, then shoveled/post hole dug the dirt out by hand to size. Put the sonotubes in, shoveled some pea gravel into the bottom of each.

The only place we used rebar was when the pier overlapped the footing on the house. We drilled a hole in the footing and stuck some rebar in it to tie the two together.

Poured 5 yards of concrete all in one go. We opted not to put the anchor bolts into the wet crete; instead, we drilled holes and put them in the next day. Easy drilling, and that way if the pier wasn't precisely where it needed to be we had some wiggle room to move them over an inch or whatever.

The first 2 photos in the link below, showing our deck build, illustrate our process.

Here is a link that might be useful: Our garapa deck

That is an awesome build! Lot of info! :)

I need to learn how to make a cement. I think they call it 3-2-1 but am not sure if I should use that for the footings.

This thread is kind of near and dear to me because I also live in a climate that requires 48" deep footings. We *just* finished digging them last weekend and have set the sonotubes in place. This weekend we are mixing the crete and pouring it in.

Weedy - what kind of bolts and post anchors did you use?

We were originally planning on 6x6 post anchors with 5/8" diameter j-bolts but we have been completely unable to find j-bolts ANYWHERE. There goes the idea of setting them in the wet concrete. So now we're drilling them in.

v1rtu0s1ty - where do you live? Also, it's good to check and see if you have any kind of rock ledge, buried foundations, etc under your yard. We actually rented a bobcat w/auger attachment which should have made quick work of the hole-making - but kept hitting buried concrete slabs that had to be removed via other means.

funyellow,

Can you please guide me about how I should make my mix? What are the materials I need? Do I need gravel to mix with concrete or was it just plain concrete?

We don't any kind or rock ledge or buried foundation. I saw how our house was built. It's clay then pour another 2-3 ft of topsoil. Our community previously was grown with corn.

Well, I am making my concrete tonight. I just plan on mixing the contents of the bag with some water :-) We are renting a mixer - NOT doing it by hand.

Some people here have said they put some gravel at the bottom of the sonotube then fill with concrete.

When you say you are putting an 8" tube, do you mean an 8" diameter tube, or setting your tube so that it protrudes 8" above ground?

Do you live in the northeast? Just curious.

I'm in Huntley. The tube length is 4 ft with 8 inches diameter. So above ground, I might protrude it 2 inch above dirt(not lawn).

I have another question. Imagine this. Let's assume I was able to complete an 18ft x 10 ft pergola with 6 legs. Legs could be 6"x6". Let's also assume that I tightened all the screws securely including the ones in the 6 base. Since the legs are just standing/screwed to the metal plate we attached to the concrete footing, is it enough to withstand strong storm/winds?

Thanks!

I hope you guys digging below the frost line know how to set sonotobes properly. If you stick them all the way down to the bottom of the hole, it defeats the purpose of digging below the frost line. What you have created is a smooth cylinder that can slide up and down with the topsoil during the freeze/thaw cycle. Pull the sonotube at least one foot off the bottom of the hole so the concrete can flow out and bond with the earth. The footing should be shaped like an inverted mushroom, not a soda straw.

v1rtu0s1ty

Very important information given by aidan_m. That's why I just filled my hole and framed the top.

If you live in Huntley, IL, then I'm about 5 miles away. My pergola is anchored with nails into the 6 x 6 throught the holes in the stand-off base. It has never had a problem in the wind though I do not have a solid roof.

Glad you butted in aidan_m!!! You are a saver. :D I didn't know about that.

Also aidan, when the concrete footing is finally dried, do we remove the concrete tube?

I remove the part exposed. It's easy with a utility knife. Wait a few days so the concrete is pretty hard and you won't mark it up getting rid of the tube