Interior Foundation Maintenance

Approximately every six months, the maintainer should make a reconnaissance-type survey of the interior of the structure for evidence of new or reoccurring problems affecting the foundation performance. If any new phenomena have developed, do not repair them without first having an engineer investigate the cause of the distress. Additionally, testing the sewer line under the slab is critical to do once every two years. If there are leaks, do not repair them until necessary leveling is done or the foundation is properly inspected.

Foundation Types

The foundation’s primary function is to provide a stable support for the superstructure, keeping superstructure distress to a minimum. A description of the types of foundations commonly used in the Southeast Texas area follows:

Slab-on-Grade: This foundation type is the most commonly used and consists of cast-in-place concrete slabs stiffened with grade beams and supported by the surface soils (includes both post-tensioned and conventionally reinforced foundations).

Pier-and-Beam: The first floor framing system for this type of foundation is built well above the ground, creating what is commonly called a “crawl space”. Typically, there is no concrete slab in this system, and the first floor is framed with wood. The “beam” is part of the framed first floor and spans from pier to pier. The “pier” in this case is an aboveground support, typically cast-in-place concrete or reinforced masonry columns.

The above ground piers are in turn typically supported on drilled cast-in-place concrete piers or cast-in-place concrete spread footings.

Following are some variations of Pier-and-Beam:

1) Perimeter Beam (Continuous Beam): This foundation system consists of a framed first floor supported on framed walls, which are supported on cast-in-place concrete grade beams.

Site Drainage

It is extremely important, particularly in areas of expansive soils, which water drains away from the foundation and not be allowed to pond against or near the foundation. The soil around the foundation should be graded to an obvious slope (two to five percent). Fill in any low spots with select fill (sandy clay) and level off any high spots.

DEFINITIONS:

Foundation is defined as a composite of soil, concrete, steel, wood, plastic, and other materials that are designed to work together to provide a stable base that supports a superstructure.

Superstructure is defined as the building components above the foundation such as the structural framing and the architectural coverings for the floor, walls, ceilings, and roof.

Foundation Design Engineer is defined as a licensed professional engineer that designs foundations (also called Engineer of Record).

Maintainer is defined as the person or group responsible for monitoring and maintaining the condition of the foundation, usually the owner or tenant.

Sand is defined as soil particles that are at least 0.06 millimeters but less than 2.0 millimeters in diameter. (Note: 1 millimeter = 0.039 inch)

Silt is defined as soil particles that are at least 0.002 millimeters (2 microns) but less than 0.06 millimeters in diameter.

Clay is defined as microscopic soil particles measuring less than 0.002 millimeters (2 microns) in diameter.

Non-Expansive is defined as a property of soil, indicating the soil particles have little potential to swell when moisture is absorbed by them and little potential to shrink when moisture is extracted from them.

Expansive is defined as a property of soil, usually clay, indicating the soil particles have a potential to swell when moisture is absorbed by them and to shrink when moisture is extracted from them. The shrink-swell movements can be in all six directions but the directions of most concern in this guide are the vertical upward (heave) and the vertical downward (subsidence) movements, as defined below.

Settlement is defined as downward movement of underlying supporting soils under load, taking with it the foundation and superstructure, and is due to the immediate elastic compression and distortion of granular or clay soil particles, and the long-term consolidation resulting from gradual expulsion of pore water from voids between saturated clay soil particles. Settlement may occur in all types of soils.

Subsidence is defined as downward movement of underlying supporting expansive soils, taking with it the foundation and superstructure, and is due to the extraction of moisture from the expansive soil particles, and consequently, shrinkage of the expansive soil particles.