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Articles by Real Estate Professionals
Home Inspections - Foundation Issues
In addition to their Articles dealing generally with the nature of their
services, the real estate professionals will discuss different specific "Topics"
of interest to buyers and sellers from time to time. These articles are indexed in
the Articles Library for your review.
Author, Edward Robinson is vice president of Professional Engineering
Inspections, Inc. He holds a degree in mechanical engineering from the University of
Houston and is a TREC licensed real estate inspector in the Houston area. You may contact
Professional Engineering Inspections's at (713) 664-1264.
Foundation Considerations
Arguably, the most significant component of the structure of a building is the
foundation. As a result of the importance of providing a quality foundation, it is often
the most expensive consideration in constructing a new home and is often the item of most
concern when one is buying or selling a home. The foundation of a home is intended to
provide a stable platform to support the components of the structure which rests on it.
Due to the expansive soils in the Houston area, providing a foundation which is strong
enough to support the structure of a home adequately while resisting damage caused by
seasonal movement in the soil and still being within a reasonable cost is no easy trick
and is one which consumes a significant amount of engineering consideration.
Consider the most prevalent types of foundations in the Houston area and what
their significant differences are. The four most common foundation types in the Houston
area are a concrete slab on grade foundation, a concrete slab on grade foundation having
piers for additional support, a pier and beam foundation, and a block and pad foundation.
The concrete slab on grade foundation supported by piers may be considered a hybridization
of a pier and beam foundation with a concrete slab on grade foundation.
A concrete slab on grade foundation consists of a slab of concrete poured into
a site built form which is partially submerged below the soil grade. It typically consists
of a relatively thin flat piece of concrete in the shape of the building which is
strengthened by grade beams cast into the foundation at regular intervals. This results in
a foundation that resembles a waffle if viewed from the underside. Reinforcing for this
type of foundation may vary significantly. The current, most popular method of reinforcing
is to install steel cables across the foundation in a grid pattern. These cables are
placed in tension after the concrete has had sufficient time to cure, placing the concrete
in compression and thus providing reinforcing to resist damage caused by bending. This
method of reinforcing is popular with tract builders who are seeking a cost effective
method of fabricating foundations and can be found in most of the tract homes built in the
last 20 years. Conventional reinforcing is used in most homes over 20 years old and in
custom homes. Conventional reinforcing consists of steel bars and wire mesh placed in the
foundation in a regular pattern to provide strength to the concrete in order to resist
damage caused by bending. Concrete slab on grade foundation are the most common foundation
type found in the Houston area due to the relatively low cost of fabrication.
Pier and beam foundations and block and pad foundations are very common in the
older parts of the Houston area, and pier and beam foundations are becoming more popular
in custom construction. Pier and beam foundations and block and pad foundations can be
similar in appearance but vary significantly in performance. The biggest similarity
between the two is that they are both foundation types that support the structure of the
building off the surface of the ground, normally resulting in some accessible crawlspace
below the foundation. The significant difference between the two is that a pier and beam
type foundation provides support for the structure on concrete or wood columns set in the
ground to a depth of 12 to 15 feet typically, depending on the soil in a given area; and
block and pad foundations support the structure on blocks of concrete resting on the first
few feet of soil at a maximum. The difference in the bearing depth of the supports results
in significantly less movement in the foundation of a pier and beam foundation because the
soil at greater depths is normally less rapidly affected by periods of wet and dry weather
which results in drying or wetting of the soil. Since soil in the Houston area expands and
contracts with changes in moisture content, this is a plus. The block and pad foundations
are sometimes used because they are much less expensive to build since drilling and
casting of concrete piers is quite expensive, and they can perform satisfactorily if
properly installed and maintained. A significant benefit of these two types of foundations
is the crawlspace they provide below the house. If there is sufficient crawlspace, it can
be used to route ductwork and to run wiring and plumbing lines. This allows for easy
changes during remodeling and, in the case of ductwork, can result in a more efficient air
conditioning system. As part of purchasing a home, many problems can exist in the
structure and mechanical/electrical systems at the crawlspace, creating a critical need
for this area to be inspected.
Each type of foundation has its benefits and its drawbacks. If possible, one
should consider these drawbacks and benefits against the cost of the house or
construction. Although some types of foundation have more trouble with differential
movement than others, most can be made to perform in an acceptable manner if properly
installed and maintained.
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