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STRUCTURAL INSPECTIONS & DEFECTS
AGE of a BUILDING - how to determine
BRICK FOUNDATIONS & WALLS
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLD POUR JOINTS, CONCRETE
COLUMNS & POSTS, DEFECTS
DISASTER BUILDING INSPECTION & REPAIR
EARTHQUAKE DAMAGED FOUNDATIONS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOD DAMAGE TO FOUNDATIONS
FOOTING & FOUNDATION DRAINS
FOOTINGS EXPOSED, Repair Methods
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CONSTRUCTION TYPES
FOUNDATION CONTRACTORS, ENGINEERS
FOUNDATION CRACKS & DAMAGE GUIDE
FRAMING DAMAGE, INSPECTION, REPAIR
GRADING, DRAINAGE & SITE WORK
GUTTERS & DOWNSPOUTS
INSECT INFESTATION / DAMAGE
MOBILE HOMES, DOUBLEWIDES, TRAILERS
MODULAR HOME CONSTRUCTION
MOISTURE CONTROL in BUILDINGS
RETAINING WALL DESIGNS, TYPES, DAMAGE
RETAINING WALL GUARD RAILINGS
STRAW BALE CONSTRUCTION
STRUCTURAL DAMAGE PROBING
STRUCTURAL WOOD ASSESSMENT
THERMAL EXPANSION of MATERIALS
TIMBER FRAMING, ROT
WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
Complex foundation movement & cracking: 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.
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This article series 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.
Also see FOUNDATION CRACK EVALUATION for a discussion of the diagnosis of specific crack patterns in masonry foundations, and see FOUNDATION BULGE or LEAN MEASUREMENTS which explains a simple method for determining how much bulge or lean is present in a foundation or wall, then see FOUNDATION MOVEMENT ACTIVE vs. STATIC which helps determine if the foundation movement is ongoing, and see FOUNDATION DAMAGE SEVERITY for a discussion of just how much foundation movement is likely to be a concern.
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.
Step cracks may also be present in bulged, leaning, or horizontally pushed foundation walls if they were constructed of brick or masonry block, or possibly (though less common) of stone.
In fact since the building foundation corners are stronger than the center portions of the foundation wall (the opposing wall at right angle resists movement of the wall being pushed), wall bulges, leans, and cracks tend to occur towards the center of the wall, resulting in step-cracking closer to the ends of the same wall.
In the photograph above, frost push has bulged the center of the foundation wall inwards; as the forces of wet earth and or frost pushing on the upper 1/3 of this foundation wall were applied at the center of the wall, the wall bulged inwards and cracked horizontally at the point of most pressure.
As the same forces causing this wall to bend were exerted closer to the building corners, the wall cracked in the step-crack pattern clearly marked in this picture by the "repairs" which have been done by filling the cracked joints. If the total amount of wall movement was minor and if the outside source of pressure (water and frost) has been corrected, further repair or reinforcement may not be needed.
In this collapsing foundation illustration, the masonry block wall has bulged inwards, portions are leaning inwards, and some of the courses of masonry blocks have slid horizontally to extend over their neighbors. All three movements are present, and of course this wall needs to be re-built.
If you think of a concrete block wall as a stack of "shoe boxes" that you're holding between your hands, and if your friend begins to push inwards on the middle shoe box, you can keep the stack of boxes intact for a while.
But eventually your accomplice applies enough horizontal pressure to the center box that the stack begins to bend. When the bending stack of boxes (or concrete blocks) bends inwards far enough to pass a critical point, the whole stack simply pops inwards and collapses.
This is how a concrete block wall can collapse suddenly when pressure on it builds past a critical point. (The same wall, if reconstructed with the addition of vertical steel reinforcing rods and concrete will be much stiffer against the same forces.)
Flood damaged building foundation walls: just as earth pressure or the increased pressure from wet earth can lead to foundation damage or even collapse, flooding around buildings can lead to foundation damage or collapse from a combination of pressure on foundation walls and perhaps loosening of supporting soils.
In flood prone areas local building codes may call for the installation of flood ports on building foundation walls to reduce the risk of building collapse. The principle of the flood vent is simple: in response to high water surrounding a building the flood vent opens to permit water to enter the building basement or crawl space, thus equalizing pressure on both sides of the foundation and reducing the chances of foundation collapse.
See Flood Damage to Foundations for details about and photographs of flood-damaged building foundation walls.
Other step cracks will of course also occur in building masonry block foundation walls and in brick masonry walls that are not leaning or bulging particularly, where frost or settlement have been causing an "up and down" movement in the foundation or footing.
We will also encounter step cracks where earth pressure or frost have pushed such a wall horizontally, breaking the masonry courses near a corner or wall-end in a stair-step pattern such as we see in this little example of water and frost damage to a brick retaining wall.
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