There are many types of foundations, but in each case the foundation’s
purpose is to provide a stable, rigid base to support the home.
It supports the frame and structure as well as protecting them from
moisture and contact with the soil.
The foundation must rest on firm ground and be protected from water and
excessive moisture. Foundations are not uniform and generally conform to the structural
standards of the time when they were built.
Whether a raised foundation or a cement slab, it is rare to find a
foundation without small cracks or some deterioration.
In most cases, the cracks are nothing to worry about and were caused by
the normal curing process or settling.
However, some cracks may be more structurally significant and warrant
additional scrutiny. Basement & Crawlspace Foundations -Because frost causes soil to shift as it freezes and thaws, the foundation
must extend below the frost line.
This may be up to four feet deep in some northern climates.
For this reason, the basement or crawlspace foundation is popular in
our area. The foundation walls rest on a footer that supports the weight of the
home.
Most modern basement foundation walls are constructed with poured concrete
or concrete block walls, although foundation walls in older homes may be
made of stone, brick, or other materials. Poured concrete walls have several advantages over foundation walls made
of concrete block in that the poured concrete is structurally superior
and not porous.
Concrete block walls are more vulnerable to the lateral pressures caused
by the soil outside reacting to moisture and temperature changes.
In addition, they are more likely to allow surface water to pass through
them and penetrate into the basement or crawlspace. Slab On Grade Foundations -Another type of foundation is a poured concrete slab.
This type of foundation is often found where the water table is high
or in warmer climates, although they may be found anywhere as a slab
foundation reduces construction costs. Generally these slabs are reinforced with steel, providing additional
rigidity and strength to the slab.
Often, plumbing, heating, and utility lines are set directly into the
slab. Slab foundations must be protected from changes in soil supporting the
slab to prevent heaving and cracking.
Excessive water can cause the soil to swell and dryness can cause the
soil to shrink, either of which can cause potential problems. Other types of Foundations -In areas where the soil conditions will not support a basement or slab
on grade foundation, there are alternative ways to provide the house with
the support it requires. Known by many different names, such as a pier, caisson, or pile foundation,
the technique is basically the same.
Vertical posts are set in the ground down to firm soil or rock.
These posts are generally constructed of reinforced concrete and are
used to support beams that become the base of the house. These types of foundations are most often found where the soil is soft
but can also be found where houses are built on hillsides or
shorelines. Your NAHIPA Member Home Inspector is familiar with each of these types of
foundations. In accordance with the NAHI Standards of Practice, we
will look for and report on any evidence of structural
deficiencies. | 
