Please help, what is the correct term for:

  1. The bottom/foot part of building or structure which carries loads from the building/structure and transfers the loads to the soil/earth/ground beneath it?

  2. The soil massive to which said load from the structure is transferred.

In my native tongue, the two meanings have different terms, however, in dictionaries they are named both base and/or foundation. The question is to distinguish the part of structure from the soil.

  • $\begingroup$ @Wasabi Thank you for editing the question. $\endgroup$ Oct 31 '16 at 6:55
  • $\begingroup$ Part 2: base is the soil upon which the foundation rests. $\endgroup$
    – Rhodie
    Jun 27 '19 at 16:52

The part of the building that is in contact with the soil is the foundation:

  1. the lowest division of a building, wall, or the like, usually of masonry and partly or wholly below the surface of the ground.

As you'll see from the same link, that might also be used for the ground itself:

  1. the natural or prepared ground or base on which some structure rests.

However, I would suggest that definition 2 (referring to the ground as the foundation) is not in use as a technical engineering definition.

I would suggest using "foundation" or "base" for the part of the structure. I am struggling to think of a good term for the soil/found on which the foundation sits. You might need to stick to simple terms such as "supporting ground". Possibly "bearing strata" or "founding strata" might be better (though maybe not applicable in all situations).

  • $\begingroup$ I actually have a hard time thinking of problems with simply using "the soil". If you're talking about foundations, it is quite clear you're talking about the soil under or immediately around the structural foundation. $\endgroup$
    – Wasabi
    Oct 31 '16 at 17:48

As was said in the other answers, the part in contact with the soil is the "foundation", or perhaps "footing" (a specific type of foundation, but there are also piles, drilled shafts, rafts - all of these are foundations).

The soil under a footing will usually be called either the "bearing surface", or "bearing strata". However, this would not apply in the case of a deep foundation such as a pile foundation unless you are specifically talking about end-bearing piles.

Other terminology you may hear and find useful in different situations:

  • soil matrix, or soil profile

This refers to the layers of soils at some location, such as you will see in a boring log.

  • bearing capacity

This is a wildly variable term that very often means different things depending on who says it. When a structural engineer asks "What is the bearing capacity?", they are almost always asking for an ALLOWABLE bearing capacity based on some limitation for settlement (often "1 inch or less"). However, bearing capacity also means the amount of stress a soil can experience before undergoing some kind of shear failure. These are related, but totally different things. Always be sure you understand what is being talked about when people start throwing around "bearing capacity".


In USA the part of structure that is in contact with earth and transfers all the live and dead load of the super-structure to earth is called foundation. Foundation is responsible to support the design loads with design settlement parameters:

Normal loads.

Shear loads.

Moment loads.

Torsion loads

And the earth under this foundation or encasing it if the foundation is set of pylons or deep caissons is called soil.

Foundation engineer design foundation by coordinating input received from soils engineer and structural engineer.

Each site has to be studied by a geologist to determine its properties with respect to its location and type of underlying earth strata and its distance from known seismic faults or expected stresses and other large scale characteristics. The geologist will give his report to the soils engineer. Soils engineer will excavate a number of test pits to measure the properties and strength of soil and gives his recommendations to foundation or in some cases to structural engineer.

In small projects on areas that have competent known soil and are flat and not near any fault line or stress line the building departments publish simplified standards that replace the job if soils engineer and foundation engineer with prescribed tables of soils load bearing and foundation's details.


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