Structural Physiology 101

physiology - the study of how molecules, cells and organs interact to form a whole being

Although the word physiology is most normally used to describe biological interactions, it has also been used in other interactions as well.  I will use it to describe some of the interactions within an occupied building structure and finally give rise to the question, “Why preventive maintenance?”

Every home is built on land that at one time was virgin ground and, as dictated by its location, climate, and thermodynamics, acclimated itself to its present pre-build state. Of course, that’s a simple description as geologists, meteorologists, and others smarter than I would have much to add.  I want to purposefully keep it simple (to within the 40 years of home building observation I have accumulated).   To do so, let me share a story…

A developer buys 80 acres of land that has been used for the last 70 years to grow various crops.  At one time the land was pristine, but over the years the top soil became depleted.   Therefore, the farmer had to fertilize it.  First, he fertilized organically using manure and tilling crops over.  Eventually, that became too expensive and unrealistic for such a large area so he started using man-made fertilizers (chemicals). These slowly but steadily destroyed the top soil even more until the only way to grow anything was to fertilize it by spraying/spreading chemicals on it.  Finally, he couldn’t grow a darn thing on it and all the organic top soil was gone.

At this point, the farmer sells his land to the developer who decides to divide it into quarter-acre lots.  After roads, utility easements and such, homes are built which are 10-30 feet away from each other.  The land, which had acclimated itself over the years to drain and grow naturally, must be landscaped to drain properly. The houses are close together with angled roofs going towards each other on the side yards.  The result?  Less land to get rid of more water.

Water… the elixir of life.

In its various forms, water can be the main enemy of a home. I say this can be because a house relies on water to keep the ground moist to maintain friction against whatever it is set in or on. The soil needs a certain amount of moisture to cause the friction or “soil expansion” which keeps the home from settling further and further into the ground.  We call this static moisture.  The soil absorbs water and expands. When there is not enough water, the soil dries out and contracts.

When we pour a concrete foundation or set piers or a footing for a foundation, the ground is dug down to below the frost line. In New York, that frost line by code is four feet.  That is how deep, if not further, that most piers/foundations are placed in New York.

The house’s piers or foundation are relying on the area of concrete touching the soil (friction).  In spring, the snow melts and the ground swells up and pushes against the concrete.  Sometimes too much water can cause heave which will lift heavy objects like driveways, foundations, floors.  Then during the summer months the soil dries out causing the soil to contract and actually leave voids where the soil no longer provides friction. When there is not enough friction to hold the weight or area, we can get what is called settling.


Every house moves somewhat, unless it has piers drilled down to refusal or set upon rock.  Even then, it will move to a certain extent because everything contracts and expands reacting to heat, cold, water, or lack of water. The majority of folks’ homes are not built upon a rock so the questions arise:

  • How wet does my soil need to be?
  • What is too much water?
  • What is not enough water?
  • And what is the failure point for my foundation?

Most people don’t think of these questions as they’re sitting in their lazy boy and say, “Honey, have you cleaned the cobwebs out of the corners lately?”  If they don’t get cracked in the head, they walk over and see it’s not a spider web but a crack in the drywall, normally over a door or below a window, but it happens in the corners too.

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