How Buildings Work


Because we have gravity, we have a need for foundations. Whether you put a stool on the ground, or build a treehouse high in the treetops, where these objects meet the surface of the earth, you get a foundation. In the previous two cases, these would be the legs of said stool, and the tree and root system your structure is attached to, respectively.

We really like building things, and, most of the time, we really like it when those built things remain where we originally constructed them. Foundations do their best to fight gravity and weathering forces to keep a building in place. As humans, we realized the need for foundations shortly after figuring out the most basic of shelter. When rain softens the ground and your small twig lean-to sinks and falls over, it doesn’t take long to look back to the cave you used to inhabit, and try to mimic those properties elsewhere.

The easiest building blocks surrounding our ancestors were plants, most often trees, resulting in simple wooden structures often resting directly on the ground. As the dynamic world around these structures kept moving, so did these early wooden creations. Slowly realization set in that anchoring more of the wood into the earth would give you added stability. Simple post foundations were born, but were limited by how far down one could dig, as well as how sturdy the wood being used was. We still build this way a lot today; a short walk down your street would find at least one fence erected in this fashion.

So stone was a natural next step, and one that we’ve kept using right up to present day. Most stone foundations are what would be called a shallow foundation, often resulting in stones laid directly on the surface of the earth, or buried a minimal distance, like the posts above. Offering greater longevity and a reduced amount of movement in changing (hot/cold/wet/dry) environments, stone became widely adopted around the world.

We learned how to apply these techniques in a variety of situations, adapting them both to location and to the desired structure. Posts could let you build above swamps and water. A deeper foundation fared better in environments with frost, and if you made them large enough, could serve as storage. Cluttered basements were born. We also learned how to use and make other materials fulfill these needs; clay and concrete in all their forms. This worked, and still works, incredibly well for small to medium sized buildings in a majority of locales where one wants to place a building. But as conditions became more extreme, and builders ambitions grew, other solutions were sought after.

Some very large buildings can be made with these primitive shallow foundation techniques. Even the Eiffel Tower sits on a stone foundation, one that is only 7-8 feet deep! (It is actually a very light structure for how visually impressive it is, part of Gustav’s ingenuity) Look at medieval castles, ancient temples, churches and places of worship around the globe; the pyramids are huge. But as we sought even denser buildings to place into what were becoming growing communities that would become villages and cities, we needed a better solution.

Deep foundations were the answer, evolving from the simpler wooden structures anchored with timber going into the earth. It was realized that the further down the pole was driven, the more rigid it became. These wooden timbers would now be referred to as piles, and grouping them together can provide support to vast structures, or supply a surprisingly solid foundation in locations with less than ideal soil conditions.

The piles rely on friction between the length of the pile and the earth surrounding it. This surface friction is incredibly strong, even against very smooth surfaces. To try at home, find a tall, non-tapered, glass, fill it with rice, and then plunge a long knife into the rice. Pulling back up on the handle will find the glass held in place by nothing but friction. This is important since early piles were smoothed down logs driven down using brute force. Reducing surface defects allowed for easier driving, and the friction was still strong enough to keep the structure from moving.

Deep foundations have grown in scale and complexity to cope with ever growing demands placed, quite literally, on top of them. We’ve employed steel and concrete, we’ve adjust shapes and sizes, and we’ve gone deeper and at innovative new angles, all in the name of building bigger structures in places that would otherwise see them topple. One hundred and ninety two piles, each five feet wide and one hundred and fifty feet long seems pretty extreme. But when you realize that supports a structure stick half a mile into the sky, on ground that is nothing but sand, foundations seem pretty impressive.