Quick Definition

The foundation is where your home meets the earth. Foundations can be made of concrete, brick, stone, steel or wood.

Media

In Depth

Some types of foundations commonly found in residential designs are:

  • Slab foundation - This type of foundation is a standard concrete slab with footers that are poured on top of the grade. Slab foundations work well in cold climates. The concrete can also serve as a finished floor – great for homeowners on a budget or those who want an industrial look inside the home. Slab foundations are not recommended in areas prone to flooding. Building up an area with fill dirt to meet city elevation requirements is unaffordable for most homeowners.
  • Pier / pile foundation – Pier and pile foundations elevate homes, particularly in areas prone to flooding. Soil conditions are an important consideration when using these foundation types.
    • Piers on grade beams - This type of foundation relies on a three part foundation system: piles driven into the ground, standard concrete grade beam poured on top of piles and piers on top the concrete grade beam. Piers are often made of concrete  masonry units (CMUs), such as cinder blocks.
    • Columns on grade beams – This type of foundation is similar to piers on grade beams, but instead of piers, concrete columns are poured and tied into the grade beam.
    • Piles – This type of foundation is the simplest type, but only is used in areas that houses cannot be built on grade. It utilizes the piles driven into the ground as the main structure. Piles are driven a specified distance with a pile driver, and the remainder is left out the ground to which the floor foundation is attached.
  • Chain Wall - This type of foundation is typically made of either poured in place concrete, or concrete masonry units (CMU). It is a wall that sits on a grade beam or slab and is a continuous wall that holds up the floor structure. These types of walls are used to raise flooring above flood zones, or to act as grade walls in a basement. Make It Right currently does not use this foundation type in New Orleans due to cost restrictions.

Our Application

In New Orleans, where flooding is frequent, almost all homes require an elevated foundation. Because of this, our homes sit at a minimum 2’ above the required Base Flood ElevationLevel of floodwater expected to occur once in a hundred years. (BFE). Because of frequent hurricanes, our New Orleans homes must be able to withstand 130 MPH winds. We tie our houses to the ground by attaching structural members to our foundation piles, driven 40’ into the ground.

Lessons Learned

On the first houses we built in New Orleans, Make It Right used a five-step process for our foundations:

  • First we dug a trench about 3’ deep and 2’ wide around the perimeter of the where the home would be.
  • Second, we drove wooden piles 6’-12’ apart in the trench.
  • Third, we formed rebar in the trench for a ground formed grade beam, with rebar projecting vertically for future columns.
  • Fourth, we poured concrete into the trench to form the ground formed grade beam.
  • Lastly, we poured columns on top of the grade beam, to which our Floor Framing is attached.

Over time, we’ve used several different types of concrete columns, including plywood square forms, steel square forms and sonotubes.

The five-step process was over-structured and used too many materials. On subsequent houses, we employed more advanced engineering techniques, enabling us to reduce the number of piles by 50% and remove all concrete work.

Today we use a two-step process: We start by driving piles 40’ into the ground using a vibratory pile driver. The structural floor foundation is then attached directly to the piles. This method has significantly reduced the cost of labor and materials.