With the approach of the dry summer weather, cracks are going to appear in and around the house, on driveways, exterior walls, and patio slabs etc. What are the cause of these cracks and what can be done to prevent these cracks?

There are different reasons for the cracks occurring in the exterior of the house or building then those in the interior of the house. For a newly constructed building usually cracks inside the house occur due to thermal expansion and contraction of the materials, these cracks are considered as "cosmetics". As the house gets older other cracks start to appear which can be due to the movement of the soil underneath the house and/or landslide if your house is on a hillside.

Exterior cracks are easily noticeable if the building exterior is brick, rock or stucco. If the wall is long a crack will occur due to thermal expansion and contraction. Thermal cracks are typically vertical in nature and follow the mortar line between bricks and rocks. Thermal cracks are usually about the same width from top to bottom.

Settlement and shrink/heave cracks are visible on the exterior wall finish of the building. Settlement cracks, which often occur due to the poor sub grade soil, are termed as "stair step" cracks; this name results from the crack "stair stepping" from one course of bricks to the next through the mortar joints.

If your house is built on clay soil it is unlikely that your home will experience some hairline cracks in the walls, slabs or driveways then a home built on sandy soil. If the width of the cracks changes with the change in season the cracks are due to the shrink/heave of the soil.

Shrink/heave soils are also called "expansive" soils. Expansive soil is fine-grained clay, which is found in almost all of Hamilton County. You can find if your house is build on expansive soil from the Soil Survey book of Hamilton County, Ohio, which is available at Hamilton County Soil and Water Conservation District.

The shrink/heave potential of the soils in Hamilton County are categorized as high, moderate and low. If your house is located in the high potential area care should be taken to minimize the effect of soil movement on foundation and slabs.

Expansive soils are subject to swelling and shrinkage of the soil, varying in proportion to the amount of moisture present in the soil. As water is initially introduced into the soil (by rainfall or watering), an expansion takes place. If dried out, the soil will contract, often leaving small fissures or cracks. Slight movement of the house founded on these soils is inevitable as a result of seasonal changes in the moisture content. Normally the whole house is affected and the homeowner is unaware that a movement is taking place. Greater movements may occur during long periods of dry weather, leading to sticking doors, windows or cracking of brick and concrete. Excessive wetting and drying causes damage due to differential settlement within buildings and other improvements.

Severe movements of the expansive soils are usually associated with trees (or, occasionally large shrubs) whose roots extracts moisture from soil. Conversely, removing a tree causes heave as moisture gradually returns to the soil. Large broad leaf trees are notorious for causing damages.

You can, however, protect your house from major damage due to movement of the expansive soil, and minimize minor cracking by taking a few precautions to ensure that the soil underneath the foundation and concrete slabs does not become either saturated or completely dry. The following guidelines are intended to assist you in that regard.

1. Install rain gutters with downspouts that drain to the street via non-erodible surfaces.

2. Planter and Yard Drainage – All areas should drain to the street. Even puddles are potential problems.

3. Concrete and Asphalt area – These also should drain to the street. Where possible water from concrete and asphalt should flow to a yard or a planter area.

4. Subsurface Drainage – Install drains if necessary to eliminate ponding. Maintain all lines clean and free flowing.

5. Landscaping- Plan carefully. Trees, even small ones, can draw huge amounts of moisture from nearby soils. Trees tend to extract moisture from soil causing shrinkage. As a rule of thumb trees should be planted at least as far away from a building as the mature height of the tree (Table 1).

6. Watering- Year round watering should be planned to avoid too much moisture in the rainy season and too little in the dry season.

7. Water should not be allowed to be ponded in flowerbeds adjacent to the foundation.