Foundation and wall cracks have been the subject of many an in- surance claim. The cause of the cracks and the time for crack
development are criterion for assessing
whether insurance coverage is extended
or denied. Cracks developing over time
may be considered wear and tear and are
usually not covered. The sudden onset of
cracks may be a result of a covered risk
such as mine subsidence, which may be
covered. The following case study illustrates a loss where very large cracks developed over a period of a few weeks.
Figure 1 shows cracks that suddenly
appeared in the wall on a more than
70-year-old home. Several other cracks
were found throughout the basement.
According to the insured owner, the
cracks appeared within a few weeks of
having initiated installation of a tile system in the basement.
Figure 2 is a view of the unfinished
installation of a drainage tile in the base-
ment. The basement wall is at the right
and a trench has been excavated to make
room for the black drainage tile shown
in the photo. The slab was cut next to
the foundation wall around the entire
basement to accommodate the drainage
tile that was then connected to a sump.
During this work, rapid crack development occurred throughout the home.
The building had been in the possession
of the insured for several years. There was
no history of subsidence in the area and
no weather-related influence that could
have initiated crack development.
Figure 3 is a drawing of a typical foundation wall design for a home. The foundation wall sits on a footing that distributes the load on the soil below to avoid
excessive settling. The drain tiles are
placed on either side of the foundation
wall. The basement floor slab plays little
role in supporting the building.
Figure 4 illustrates the foundation situation that is the subject of this loss. The
insured’s old home had a raft foundation
design where the foundation wall is located on top of the slab and relies on the
slab to distribute the load to the sub soil,
Figure 4A. The home did not have a drain-
age tile system and the basement floor
would often be covered with puddles from
heavy rains. This motivated the insured to
install a tile system. Figure 4B shows the
excavation performed by the insured. The
slab has been cut along the perimeter of
the floor slab to make room for the drain-
age tile. No building permit was obtained
for this work. The load-carrying capacity
of the slab has been removed and the much
reduced bearing area of the wall base has
caused additional pressure against the sub
soil. This was sufficient to cause rapid set-
tling of the foundation wall as illustrated
in Figure 4C. The insured had significant-
ly degraded the load-carrying capacity
of the foundation wall, resulting in rapid
settling and crack generation throughout
the building. This was not considered a
covered loss, in this case.
Charles C. Roberts, Jr., Ph.D., P.E., is president of C. Roberts Consulting Engineers,
Inc., which provides professional engineering services in accident reconstruction,
failure analysis, fire causation, explosion
analysis, and biomechanics. He may be
reached at email@example.com.
in Crack Growth