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DISASTER BUILDING INSPECTION & REPAIR
EARTHQUAKE DAMAGED FOUNDATIONS
FIRE DAMAGE vs MOLD DAMAGE
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
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FOUNDATION CRACKS & DAMAGE GUIDE
FRAMING DAMAGE, INSPECTION, REPAIR
GRADING, DRAINAGE & SITE WORK
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PORCH CONSTRUCTION & SCREENING
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RETAINING WALL DESIGNS, TYPES, DAMAGE
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SINKHOLES, WARNING SIGNS
STAIRS, RAILINGS, LANDINGS, RAMPS
STRAW BALE CONSTRUCTION
STRESS SKIN INSULATED PANELS
STRUCTURAL WOOD ASSESSMENT
TIMBER FRAMING, ROT
TRUSSES, Floor & Roof
WATER ENTRY in BUILDINGS
WOOD STRUCTURE ASSESSMENT
Determine active vs. old building foundation or structural movement: This article explains the difference between active & static foundation movement: how to detect & diagnose active movement or movement cracks in a building foundation.
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. Types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history, and other evidence of building movement and damage are described to assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from those likely to be important and potentially costly to repair.
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MOVEMENT ACTIVE/STATIC - Foundation Movement: Determining Active or Dynamic (ongoing movement) vs. Static (no ongoing movement)
The photo at the top of this page shows a bowed masonry block foundation wall with horizontal cracking that occurred due to earth loading at the time of construction, probably by vehicles driving too close to the foundation wall shortly after it was constructed. At this website we explain how it is sometimes possible to be confident about the cause of foundation damage which in turn helps assess the risk presented to the building.
Photographs of types of foundation cracks and other foundation damage: we have a large library of photographs which we're in process of adding these photographs to this website. Pending completion of that work, contact the author if assistance is required.
How to evaluate the extent and importance of building foundation movement
How to determine the age of foundation cracksLook for clues indicating old vs. new cracks and active vs. static cracks. For example, evidence of repeated repairs (patched, re-cracked, re-patched) is clear indication of recurrent movement. Evidence that a crack occurred at time of construction (in an older house, such as wavy mortar which "bent" in the mortar joints as a wall was loaded) is clear indication of an old condition which may or may not be accompanied by other evidence of later movement.
How to look for evidence of horizontal foundation movement or wall displacement
Horizontal wall movement: Look for evidence of horizontal wall displacement, lateral displacement such as frost push of a masonry block wall. The bottom block course, held in place by the floor slab, may be in the original location while the first course above or higher courses may have been pushed horizontally inwards.
How to evaluate foundation wall leaning, tipping, or bulging
Wall tipping or leaning: Look for evidence of wall tipping or leaning - the entire wall has remained flat but leans inwards at the top.
Wall bulging: Look for evidence of wall bulging, locate the center of the most bulged-in section and note its height above the bottom of the wall and its relative position to the top of grade outside.
How to measure the amount of lean or bulge in a foundation wall
Measuring foundation wall tip, lean, or bulge: is simple: drop a plumb line near the most-bulged area (usually the center) of the wall, perhaps fastening it to
a nail in a floor joist overhead, about 4" in from the wall. Measure from the string in to the wall at various heights up the wall.
Details: a plumb line, that is a string suspended by a weight, gives a perfectly vertical line from which to measure back to the wall surface. We don't care about the absolute value of the various measurements, we care about the difference between these measurements. Usually the very bottom of a building wall will not have moved inwards, particularly if a concrete floor has been poured against the foundation.
The entire building floor slab is acting as an "anchor" to hold the bottom of the foundation wall in place. So we take the distance between the foundation wall and the string at the bottom of the wall as our "home base" or point of assumed "zero movement".
We compare this measured value with the other measurements between the wall and the string. If the foundation wall or any part of it higher than the floor has moved, tipped, or bulged inwards, those measurements from wall-to-string will be less than the distance, wall-to-string measured just above the floor level. That's because the wall has moved inwards, towards the string.
An example of measuring the amount of foundation wall bulge inwards
How to distinguish between a "bulged" foundation wall and a "leaning" foundation wall, and why we care
Characteristics of a leaning foundation wall
If all of our measurements of inwards movements in the foundation wall increase in distance (wall to string), from floor up towards the top of the wall, the wall is leaning inwards. In this case we'd expect to not see horizontal cracks (if the wall is masonry block, for example).
Characteristics of a bulging foundation wall
If our measurements anywhere between the floor and the top of the wall is greater than the distance measured (wall to string) at the floor bottom and at the wall top then the wall is "bulged" inwards at that point. If the wall is masonry block in construction we'd expect to see horizontal cracks in one or mortar joints in the bulged area, with the widest horizontal crack at or close to the point of greatest inward bulge.
Even a concrete wall which is bulged is going to be cracked horizontally, though perhaps not in such a straight line. But a bulged reinforced concrete wall would be very rare unless perhaps the concrete wall bulged, or its forms bulged, during the time that the concrete was being poured and was still wet.
Other cases of leaning or moved foundation walls may produce different measurements
Horizontal foundation wall movement, creep, non-leaning lateral shift
On less frequent occasions we've found that an entire masonry block wall (or portions of it) were pushed horizontally inwards by some outside force, without causing the wall to lean or bulge. In a pure example of such a case, all of the differential movement measured (wall to string) between the wall bottom point (held in place by the floor slab) and the inwards-pushed wall section, will be a horizontal movement of that portion of the wall, and if it's masonry block, you'll see that the inwards-moved blocks are "hanging over" or projecting past the surface of the masonry blocks that did not move.
Combinations of foundation wall movement
You may encounter a foundation wall which has moved inwards in a combination of forms, both bulging at its most-pushed-in point (with horizontal cracks in the foundation wall) and the wall may have also been pushed inwards sliding some of the masonry blocks inwards past others which have remained in place.
In this case you'll see both that some masonry wall blocks will overhang or protrude past others in the wall (usually upper inwards pushed blocks hang over lower more stable blocks closer to the floor), and there may be bulging and cracking at another elevation of the wall.
Step cracks in building foundations 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.
Other step cracks will of course also occur in building masonry block foundation 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.
Other vertical cracks can occur in a masonry block or concrete or brick or stone foundation wall without leaning or bulging if the wall is moving due to footing settlement or frost.
When we find visual or measured evidence of cracking and movement in a masonry foundation wall of any type, there are some diagnostic questions we can ask that help assess the cause of the problem and the urgency of repair actions:
NOTE: without historical data these causes can be difficult to confirm without monitoring. Active movement requires at least monitoring; present or future repair steps likely.
Continue reading at FOUNDATION MOVEMENT COMBINATIONS or select a topic from the More Reading links shown below.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
NOTE: Journal of Light Construction articles are available on CD ROM from the Journal of Light Construction, www.bginet.com, 802-434-4747
Opinions herein are the responsibility of the author. Most of this material has been subject to ongoing peer review but is without any professional engineering analysis. Home inspections may include the discovery of defects involving life, safety, and significant costs. Home inspectors who are not both qualified and certain of the authoritative basis of their conclusions should obtain their own expert advice from qualified experts.
This work is also based on the author's construction & inspection experience, training, research, and survey of material from ASHI, and from N. Becker, R. Burgess, J. Bower, D. Breyer, A. Carson, J. Cox, A. Daniel, M. Lennon, R. Peterson, J. Prendergast, W. Ransom, D. Rathburn, E. Rawlins, E. Seaquist, and D. Wickersheimer. Some useful citations are at the end of this paper.