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Excavation is required to create trenches where concrete grade beams can be built.  A concrete grade beam, or continuous footing,  is a wide steel-reinforced concrete beam in the ground (usually the top is around 6-18″ below grade) that transfers the vertical loads of the building to the soil.  To prevent the building from compressing the soil, and therefore sinking, the beams are wide to distribute weight.  The beams for this house ranged in width from 18″-36″, and are about 24″ deep.  A geotechnical soils report is usually required in New Orleans (where the soil is expansive and pretty unreliable) to allow the engineer to have confidence in designing a foundation of this type, but luckily my engineer recently had a project in the area where he had a soils report done.  This allowed me to avoid using wood friction piles which would’ve been more expensive  (probably an additional $5,000 at least) , and potentially disruptive to my neighbors historic and fragile homes.  To mention, friction piles are commonly used (and usually required by code) in New Orleans for foundations.  They are basically treated telephone poles driven into the ground by a pile driver.  Because the bedrock is to far below the surface of the ground, “end bearing piles” cannot be used.  Friction piles bear the load of the building through the cumulative value of all the surface friction on each pile.  Based on the weight of the building, and the specific point loads, a grid of piles is driven, and grade beams are then poured onto the tops of the piles.  Anyways.

A lot of soil was removed.  Bricks from the previous structures foundation were buried throughout the site, but it wasn’t really an obstacle because the mortar had long since corroded and left most of the previous brickwork dismantled.  It should due mentioned that in New Orleans bricks were historically used for the foundation, and were commonly done as “spread footings.” Much like grade beams, spread footings distribute loads to the soil.

Broken bottles, a horseshoe, and an army recruiting coin were the notable discoveries buried within the soil.  Overall, nothing all that interesting.  At the completion of excavation, the dirt was in the way, so the contractor decided to have the dirt hauled off.  This, I believe, is turning out to be a mistake.  The site had a good topography before construction.  It had a gentle slope toward the street in both directions, leaving little possibility for ponding.   Stay tuned for the resolution of the site grading issue.

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