Integrated Buildings & Structures

Hi, I am about to build a concrete footing for steel elevator but I have to excavate 1.5 m under the ground to reach the stable soil the thickness of the concrete footing is 0.5m now I am asking it is okay to let part of the steel elevator under the ground or I should build concrete columns to reach the ground level to fix the steel elevator on it???

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Abu Ahmed Aff.M.ASCE
Al Jazera State
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If the steel framing for the elevator is set on the footing with the top of footing below grade, and soil is to be placed around the columns from grade level to the top of the footing, the steel framing below grade can be coated with a layer of epoxy paint or bituminous coating and then a 3-inch (75 mm) minimum layer of concrete, built as a square or rectangular pier, can be cast around the steel framing.  Any slab-on-grade work at the grade level can be poured up against the concrete pier.

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Dennis Young P.E., M.ASCE
Owner/principle
Young Engineering, LLC
Omaha NE
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Look at the building architect's plans.

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Stacey Morris P.E., M.ASCE
ETI Corporation
West Memphis AR
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As Mr Young point out, burying steel is generally not a good idea and the protection he suggested works very well.  There are many variables to consider such as future access, clearances for machinery, and the steel details for the elevator.  Bringing the concrete up to grade to meet the elevator steel is also a good option.  The third option is to construct concrete walls around the footing to create an elevator pit the same way you would construct a basement.  The choice between the three options is based on the building details, cost, and future maintenance needs.  With the elevator pit or concrete to surface all of the steel is accessible for future maintenance or changes to the building.  Discuss the options with the building architect or owner to see how each option fits in with the building design and budget.

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Darin Gatti P.E., M.ASCE
Chief Engineer
Philadelphia PA
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Just build a concrete pedestal, is it a common practice?

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Qingsong Shi Ph.D., P.E., M.ASCE
Senior Structural Engineer
Richtech International Eng Inc.
Katy TX
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When I was young I devised a clever foundation and got some advise from the architect that has stuck with me.  "Dig big hole, pour concrete in it"  The labor to build the piers is probably more then the cost of pouring another meter of concrete in the hole.  Burying steel in the ground is never a good idea.  If labor is cheap and material very expensive, your solution may be viable.  I would consider using a grid of intersecting walls to form the column supports. This would provide much simpler rebar detailing over piers.

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Donald Lee M.ASCE
Struct Engr
Don Lee Engineering
Lakewood CA
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