What is a basement foundation?



Basement foundation is the load supporting and distributing system of a house or building.


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The foundation system or substructure consist of a foundation wall which provides lateral support against the forces of the earth, backfill and hydrostatic pressure.

A basement's foundation is useless without its footing.

A footing allows the force (weight) which travel from the upper level

  • floor assembly
  • roof structure
  • occupant of the building

through the foundation walls to be distributed to the earth without causing major settlement of the structure.

Both the basement foundation wall and footing provide mean of load transfer from the upper floor to the earth.

Types of foundation used in Residential and light commercial building.

In keeping this simple, there 3 types of substructure typically used in the construction a basement.


Basement

For the most part, in seasonal climates residential houses and light commercial buildings are constructed with full depth foundation system (substructure)which form the basement.

The depth of the basement will depend largely on it usage and regulated by local building codes to ensure minimum height requirement are implement.

This ensure that living spaces--example a basement apartment--in the case of a residential house can be usable.

A light commercial building depending on the usage, could be built with to full depth basement to accommodate parking etc.


Crawlspace

Another type of substructure is known as a crawl space. A crawl space isn't design to accommodate occupants but to allow easy installation and repair access to services (gas, water, ect.).

The crawl space of a home can be heated or unheated. Heated crawl space adds comfort for occupants.

Building codes set the minimum requirements for the height and resistance-value of a heated basement.


Slab-on-grade

Last of the three commonly used substructures is the slab-on-grade. This type of basement foundation is primarily on tool shed and dog houses in cold climates.

The reason for it limited usage is the depth to footing.

Slab-on-grade unlike basements and crawlspaces are consist of a perimeter footing which supports a slab-on-grade, hence the name.

This form of substructure is commonly used in warm climate because there is no need for freeze protection.

Freeze protection! What is it?

Seasonal climate presents a unique challenge, since during the fall and winter the earth freezes and spring and summer it proceeds to thaw.

As a result of this cycle settlement of the substructure can be amplified. This can be detrimental to the integrity and longevity of the entire building.

Freeze protection is paramount in cold climate for this reason.

Eliminating settlement casued by freeze - thaw cycle

In cold climate it recommend that all foundation footing be place below the frost line. The frost line is that point at which the earth below the surface.

The issue regarding depth of a footing should be addressed in the local building codes. If your situation is unique, seek advice for an accredited Engineer.

Interested in learning more about the detailing process of a basement foundation click here to gain information on how it correctly detail a foundation plan.

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