How to Detect, Diagnose, & Evaluate Earthquake Damage to Building Foundations InspectAPedia® -
How to Evaluate and Diagnose Complex Combinations of Foundation Movement Cracks, Bends, Leans, or Shifts in Foundation Walls
Different causes of foundation leaning, bulging, cracking, creeping, tilting, sliding, or other movements, what they look like, how to fix them.
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This chapter of the "Foundation Crack Bible" discusses in detail the recognition of different types and causes of complex or combined building foundation
movement and foundation damage. We distinguish among vertical movement, horizontal movement, leaning, tipping, bending, differential and
uniform settlement, earthquake and storm damage, and other foundation damage patterns.
Our "Foundation Crack Bible" document, of which this web page is a chapter, describes how to recognize and diagnose various types of foundation failure or damage, such as
foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.
To be used properly, this information must be combined with specific
on-site observations at the particular building in order to form a reliable opinion about the condition of that building's foundation. Anyone having
concern regarding the structural stability, safety, or damage of a building, foundation or other components, should consult a qualified expert.
Photographs of types of foundation cracks and other foundation damage: we have a large library of photographs which
we're in process of adding to this document. Pending completion of that work, contact the author if assistance is required.
Combinations of Building Foundation Movement due to Earthquake, Flood, or Storm Damage
Earthquakes shake building structures in different patterns, sometimes unique to a particular quake. The basic movements are side to side, up and down, or a combination of these. Depending on which forces are exerted, buildings shift and structural components fail in different patterns.
The photographs of earthquake-damaged building foundations and structures shown here are rather dramatic (and terrible as there were certainly fatalities in these buildings). More subtle is the detection of small movements, not immediately obvious, that break gas mains or cause other dangerous building conditions following an earthquake.
At the Northridge Earthquake a sideways shift was visible on many buildings. Force was sufficient to shift some entire buildings sideways in distances ranging from just an inch or so (broken gas mains, gas explosions, fire, burst water mains) to distances up to eight feet (where buildings were leveraged sideways as supporting columns failed).
In the photo just below, lateral movement caused the failure of supporting columns. Some building sections collapsed straigth down (photo below) while others were levered sideways by their supporting columns, moving sideways for a distance about equal to the height of the failing columns.
Our photo shows one of the bent, failed Lally columns. The building wall in the background of the photo was previously supported on top of this column.
Vertical movement due to earthquake: The Northridge Earthquake in Los Angeles, California in January 1994 caused extensive damage
as well as fatalities when buildings were shifted off of their foundations, leading to catastrophic collapse in some cases.
This photograph
taken by the author at Northridge Meadows, a site of some of the worst fatalities, shows a section of building that collapsed straight down, compressing
the first floor (and some occupants) to just a few inches.
The left portion of the photo shows a third floor balcony aligned with the
second floor balcony of a building segment that did not collapse.
Earthquake resistant construction has as a primary objective
to prevent just this sort of collapse, as an effort to reduce the number of injuries and fatalities from an earthquake.
In this photograph, taken from the rear of the building above, the movement caused by the Northridge Meadows earthquake is more clearly demonstrated. Notice that the bent Lally column top shows that the column was hollow?
Structural engineers and experts with more experience than the author have examined this catastrophe. But we thought it worth noticing that some of the Lally columns that failed were hollow steel posts while others that remained standing at the same building project were ones that had been filled with concrete to resist bending. We wondered if the schedule-pressure of original construction at Northridge Meadows contributed to use of columns that were not what was called for.
Horizontal movement due to earthquake damage: The Northridge Earthquake in January 1994 also caused extensive damage
when its lateral thrust caused some buildings buildings to be shifted off of their foundations.
This photograph shows an easy-to-determine
case of significant lateral movement of a wood frame structure. Often an improperly secured crawl space cripple wall simply leaned
over, levering the building to one side for a distance equal to the height of the collapsing (cripple wall).
In this case the collapse
was of a wood-framed supporting wall, not a masonry foundation.
Combination of movements due to earthquake damage is demonstrated by this photograph of an unreinforced stone masonry foundation and
wall home in California.
Unreinforced concrete structures are no longer permitted by California building codes for construction in areas of
earthquake risk.
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Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
"Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
Sal Alfano - Editor, Journal of Light Construction*
Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and some of the foundation inspection photographs cited in these articles
Terry Carson - ASHI
Mark Cramer - ASHI
JD Grewell, ASHI
Duncan Hannay - ASHI, P.E. *
Bob Klewitz, M.S.C.E., P.E. - ASHI
Ken Kruger, P.E., AIA - ASHI
Bob Peterson, Magnum Piering - 800-771-7437 - FL*
Arlene Puentes, ASHI, October Home Inspections - (845) 216-7833 - Kingston NY
Greg Robi, Magnum Piering - 800-822-7437 - National*
Dave Rathbun, P.E. - Geotech Engineering - 904-622-2424 FL*
Ed Seaquist, P.E., SIE Assoc. - 301-269-1450 - National
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