Building Foundation

This is how they install building foundations in southern Louisiana.
All of this area use to be water and over thousands of years it was filled in by Mississippi river silt.
So it is not the best building site. In fact if you dig just a few feet and leave the hole overnight it will be full of water when you return in the morning.

They start by hauling in river sand we pump out of the Mississippi to build the land up to the desired elevation. So yes that is Iowa or some other states dirt.




For big commercial sites they may even stack dirt on the site 10 to 15 feet high and use the weight of the dirt to compact the grade that will be used. They will also bring in a pile driver and put in 3 or 4 test piles to see how long the piles need to be. They count the blows needed to drive the pile 1 foot and once they reach the desired resistance they now know how long the piles need to be.
For a small commercial one story building like will go here or a house they just go on past experience for how long the piles need to be.

Once the dirt is compacted from it raining on it for several months they bring in a pile driver.



As you can see they have 2 different grades and lengths of piles for this job.
For a house they would just use the long piles in the foreground but they would be treated like the ones in the background.







For this commercial building; since there looks to be about half as many short high treated piles as the long ones; we can assume the will cut the short ones in half and stack the half on top of the long one.
They will use these connectors to hold the two piles on top of one another.




They can use to lesser treated piles for the bottom because there is no chance of them ever seeing oxygen again. While the upper piles will be under a slab there is still a chance of some oxygen getting to them due to ground settlement.
Without these piles the slab would settle and crack.
There are some neighborhoods where you can see under the edge of the slab because the whole yard has sunk and no fill has been added as upkeep.

I have been involved in a few jobs that piles were driven. On bridge abutments we drove to total refusal. As you said some specifications called out a specific downward distance per hammer drop. I did not know it was sop on residential and commercial construction in parts of La. Thanks for the tour, and by the way, all that Mississippi silt is not from Iowa. Plenty of states between Iowa and La. and most of them have soil of some kind washing away. gobble

Its common in the metro NYC area as well, depending on the site, these are 2 contractors I've been on sites with years ago.
Falco

Linde Griffith

that's from our farm where Granpa plowed these Ozark hillsides... bring it right back, I need it.

Very interesting John. Thanks for posting. I would have thought the wood would rot below the surface.

Pretty much the same on Long Island---many waterfront homes are elevated on treated piles to get the first floor above the 100 year flood plane--on bridges we use untreated timber piles where the tops are well below water--otherwise we use prestressed concrete piles----for bridges we use load tests on the piles to verify the length. The ENR pile driving formula for blow count can be very unreliable at times---especially in fine waterlogged soils

John in La,
So all your foundations have a PHD degree, Piled Higher and Deeper.

Interesting post.

I was in Florida and watched them build a boat dock in a canal using water injection. They put a treated post in the water, pumped water around post. The post sank in the mud until it hit bed rock. Now keep in mind a guy wearing waders was holding the post, another injecting water, a third watching out for gators.

When I lived in Anchorage back in the mid 80s I worked as a welder a couple of winters for a foundation company.
There because of the permafrost they use a pile driver to drive 6" drill pipe into bedrock.
Then we set I beams on top and welded them on for homes and townhomes.
All used pipe that was Highly magnetic.
Had to learn how to weld that stuff.
They worked most of the winter but their regular crew wanted to go south for the cold months. So I worked winters and did other stuff in summer.