Editor’s note: The extreme temperatures and moisture levels of this past year may cause cracks in building foundations, but that can be prevented, according to M.J. Hensley, civil engineer and member of the Pea Ridge Planning Commission. He said: “I’m dedicated to making life easier through the workings of engineering and the materials God gave us. A lot of people don’t understand that.”

When buildings, pavements or any other structures are constructed, one of the factors to consider in the design is the environmental conditions that will prevail during the design life, which is often 50 years or more. Houses are no exception to this procedure. Houses or any other building have a foundation, sometimes referred to as the footing, which ultimately carries the load.

The environmental factorconsists of two categories: temperature and moisture.

The coldest expected range of temperature is considered for the optimum depth of the footing.

The common term for the minimum safe depth is referred to as the frost line or penetration depth. This information is printed on area maps of the country using isogonic lines to represent the various frost depths.

According to published information, the frost depth is about 18 inches on the average in Pea Ridge.

The second factor of moisture is how the prevailing soil will react to the moisture content of the soils throughout the life of the structure. Foundation soils are compacted to optimum moisture prior to placing the footing. The various types of soil present can react differently to the moisture and temperature for any given area.

Sometimes this condition can change in a very short distance. In-pace soil moisture contents can vary froma low of 2 or 3 percent to over 30 percent. The low range represents the sandy or loam type soils while the higher would represent the clay type soils. Soils containing a high amount of clay or red type dirt can have as much as 30 to 40 percent volume change with a change in the moisture content. This could be swelling or shrinkage depending on which cycle is occurring. Placing the foundation to the appropriate depth will help provide a constant moisture content and prevent any freeze damage.

The past years’ weather has been anything but usual for the Pea Ridge area.

The temperatures were much colder and lasted much longer than normal.

These conditions cause the underlying soil to swell about 20 percent. Typically, anything that freezes expands. By the freezing being more severe than normal, the depth of frost goes deeper and lasts longer, which is basically an icelens. Typically, the frost begins to thaw in late March or early April and water can be seen oozing out of soils or stone base material during this period. This is called spring thaw and soils are the weakest and least capable of carrying the design loads during this period. As the materials thaw, voids are formed in the soil because of the expanded condition of the material.

Typically, the spring rains begin about the same time as the thaw occurs.

The voids are then filled up with water, creating a saturated condition of the soil. The saturation condition makes the soil even weaker than the frozen condition. More swelling is experienced. These are all cyclic conditions and are expected to happen annually.

The problem is the extreme, which is what the recent drought condition brought. Structural damage can be caused from too much cold weather or too much dry weather.

As previously mentioned, clay soils can change volume by as much as 30 to 40 percent. Prolonged dry weather can produce foundation cracks due to the shrinkage of the foundation soils. These cracks will appear as stair steps in masonry foundation walls of block or brick. The steps will be diagonally upward and generally around the third or end points of the structure. The cracks will appear at first as hair-line size, but will grow with time and open to a half an inch or more. Once the foundation is cracked, the cracks are live, that is they continue to work annually and will grow much wider.

Many of these type cracks never amount to much of a problem. In severe cases, the interior wall plaster or sheetrock will crack under the stress. As the foundation begins to shift with the movement, doors won’t open or close well, windows won’t raise because everything is out of square. Corrective measures for this type home damage is extremely expensive.

Everyone is encouraged to walk around house and inspect it for these type cracks on the walls and around the doors and window openings. Watering around the foundation can help prevent damage. The process is ongoing; watering the foundation is not a cure for the problem but it’s prevention.

In the current weather pattern in the area, concrete sidewalks will buckle and concrete pavements will simply blow-up. This is all related to the previous wet spring and the current drought conditions.

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Editor’s note: M.J. Hensley is a retired civil engineer, was Arkansas engineer of the year in 1970, and is a member of the Pea Ridge Planning Commission. He has assisted city employees with drainage and street projects, offering them the value of his engineering expertise.

News, Pages 7 on 08/17/2011