Home Building Articles
July 08, 2009
You may recall the story of the statue built with clay feet. Even though the head,
chest, and legs of the statue were made of strong metals, it only took a single
stone to bring the statue down. The same concept is true of new homes. All the best
practice building in the world won't make a home durable, comfortable, or safe if
the soil beneath it is unstable.
Poor quality soil is a real issue for builders today. If not recognized and addressed,
shifting or expansive soils, or soils rich in clay, can lead to structural compromises
within the home. Landscaping and the home's grading can also suffer, resulting in
pooling of irrigation waters and poor storm run-off. Before construction begins,
the best practice is to research and assess the soil quality for its ability to
bear the weight of the building.
In most cases it's a good idea to hire a soil engineer to inspect and evaluate the
soil conditions. A soil engineer can determine the depth to ground water, settlement
characteristics, and what is needed to bring the site up to code. But before calling
in the engineer, it can be easy for the builder to inspect the site and make some
early determinations on soil quality of their own if they know what they're looking
There are two main factors to consider when assessing soil quality, type and substance.
"Virgin" and "fill" are the two main types of soil. Virgin soil has never been disturbed
and may be easier to work with than fill areas. In general virgin soil will be more
compact and more consistent throughout the building site. Land that has had fill
brought in may need to be compacted. Because you can't be sure of the quality of
fill used in the area, a soil engineer can be very helpful in areas with extensive
When trying to determine the substance of the soil or what the ground consists of,
here are a few tips:
Walk around the site and if the soil is soft try driving a stake into the soil.
If the stake drives easily with only two or three hits from a hammer, chances are
the soil contains fill and will have to be compacted.
During excavation take a small handful of damp soil and roll it into a ball between
If the soil crumbles and won't retain its shape it means the soil should be well
draining and contains a sand and gravel mix.
If the soil sticks together in a ball shape it's probably silt.
If you are able to roll the ball into a pencil shape or if the ball stays together
when dropped from a few feet, the soil probably has clay in it. Soil containing
peat or expansive clays are the worst kinds to build on, and a soil engineer would
probably suggest you remove the soil from the site before building. Areas prone
to earthquakes and landslides are especially susceptible to poor soil quality, and
special care by the builder needs to be taken to help protect the homeowner for
catastrophic building failure. Unlike the sculptor of the statue with clay feet,
builders today have the technology and resources readily available to build a home
with a solid foundation.