I need to pour 5 footings for support underneath a 3-season porch and a deck that reside 4 feet above grade. Footings will be ~10-12" wide and 4' in-ground. I plan on d-i-ying it and would like to know what do I need to know before starting to mix. This will be quite a number of bags by my calcs, so I plan on renting a mixer.

Is it ok to pour directly into the dirt hole or do I need one of those fancy forms?

I've read the contact material should be wet before putting the concrete in/on?

How long should it cure before applying load to it (i.e., building the deck)?

Should it be covered w/ plastic and moistened as it cures as I have read?

Any special type of concrete to use for this application or will cheap stuff work?

Other hints to make it easier or "what not to dos" would be helpful. Thanks in advance.

 

Have you consisered using sonotubes under the posts?

Sonotubes are heavy duty waxed tubes used as forms that stay in place unless you strip it off the concrete above grade.

With Sontubes, you use a post hole diigger/auger or a shovel to dig the hole. Set the tube in place with top at the desired elevation and then backfill. Pour in the concrete and insert a Simpson connector in the wet concrete.

Advantages are less excavation, less concrete with no extra for the over-excavation. Tubes are available in 2" increments from 8" to as much as 24" or more.

Dick

 

Thanks Dick. Yes, what you describe is exactly what I intend on using. Thought that would give a nice appearance to the 1' of concrete above the grade. The holes I have hand dug (didn't know for sure where electrical, septic, gas line were so didn't want to risk using the auger, and that turned out to be a good idea). Was originally going to put the tube in the hole which I have dug in a very nice circle for the most part. Got to thinking that if I could fill the hole without using the tube then I would not have to backfill around the tube which would be difficult if it was a tight fit at the top and "sloppy" at the bottom. And possibly this strategy would have less settling to worry about after the fact?? What I didn't know is if there were any reasons why concrete could not come into contact w/ the dirt in this situation or if there was a specific "kind" of concrete that would be better served here. Have done it before putting up clotheslines and basketball hoops, but that is far less serious than having a 12'x14' covered porch start leaking away from the house because of poor footings.

And check on the anchors too.

 

The Sonotubes a more professional appearane for the 6" to 12" above grade. They also require a lesser amount and more predictable amount of concrete. You would probably need an 8", 10" or 12" Sonotube it you use the Simpson brackets. The brakets ate to keep the wood posts out contact with the soil.

There is also a minor technical advantage. Because the slides are smooth the soil will not stick to the tubes. A rough surface (in some types of soil) can raise a rough surface as the frost goes down.

You do not have to compact the backfill soil around the if it is decent granular soil. Just fill well an mother nature will take care of it. - You really have little lateral load on a tube foundation.

You can pour any type of concrete (3"-4" slump) against the soil, but you just need to buy, haul and mix more.

 

What is the rule of thumb on curing? Covered or no? I presume at least a couple of days before I would want to attempt building onto the anchors?