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How to Detect, Diagnose, & Evaluate Foundation Movement, Cracks, Damage StructAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com

• How to Evaluate and Diagnose Foundation Movement by Type & Location of Cracks, Bends, Leans, or Shift in Foundation Components
• How to distinguish foundation bulging from foundation leaning
• Different causes of foundation leaning, bulging, cracking
• How to recognize foundation impact damage
• How to recognize foundation creep or footing movement

This chapter of the "Foundation Crack Bible" discusses in detail the recognition of different types and causes of 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. 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. 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.

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FAILURES by FOUNDATION MOVEMENT TYPE
  VERTICAL MOVEMENT IN FOUNDATIONS
    Differential vs. Uniform Settlement Cracks
    Vertical Cracks
    Uniform Width vs. Tapered Foundation Cracks
    Diagonal Cracks in Concrete Foundations
    Diagonal Step Cracking in Masonry
    Leaning or Tipping Buildings
  HORIZONTAL MOVEMENT IN FOUNDATIONS
    Bulging, Leaning & Sliding Wall
    Impact Damage to Foundations
    Horizontal Foundation Creep
    Horizontal Movement & step cracks in brick
  COMBINATIONS OF FOUNDATION MOVEMENT
    Wall bulge & step cracks
    Foundation Movement During Collapse
    Foundation Movement due to Earthquake
    Other Foundation Step cracks
  BULGED vs. LEANING FOUNDATIONS
  Thermal Expansion Cracking in Brick

Vertical Movement in Foundations & Walls

Vertical movement in foundations, in the most general cases, is caused by downwards movement of the wall or wall footings such as when a wall footing sinks in soft soil, or by an up and down movement of the wall or wall footings such as when a wall is disturbed by frost in a freezing climate or by expansive clay soils which expand or shrink as their water content increases or decreases. Here are some classes of vertical foundation or building wall movement which we illustrate and discuss in more detail below:

• Differential foundation settlement: one portion of a building foundation or wall moves up or down separately from its neighbor.
• Uniform building settlement: an entire building moves up or down together, causing little or no foundation cracking or damage, though there could be important damage to mechanical connections to the building and even dangerous gas line leaks.
• Building tipping or leaning: an entire building tips or leans out of level.
• Eartquake or Storm Damage to Buildings: can cause complex building movement in multiple directions, as we illustrate below.

Differential Settlement vs. Uniform Settlement in a Foundation Wall

Differential settlement in a foundation or wall:: We use the term "differential settlement" to describe a condition in which one portion of a building foundation is moving down, (or up and down) at a different rate or in a different amount from other portions of the foundation or wall. Differential settlement will damage the foundation or wall by producing (usually vertical, possibly diagonal or stair stepped) cracks and other symptoms of wall movement. The large foundation crack in this poured concrete wall was caused by differential settlement in a new foundation wall. All of this movement occurred during the first 13 months after the home was built.

Differential settlement in a building slab or supporting piers can produce significant and recurrent cracks in the living area as drywall and trim are torn and dislocated during building movement. This photograph shows a significant crack in an upper floor interior wall which was bending as the center of this home settled downwards. The home had been built over the site of a previous stream bed. Its basement floor slab and supporting piers was settling downwards at its center. There was some additional movement in some of the building perimeter foundation walls, but the most significant settlement was at the center of the basement floor.

Uniform settlement in a foundation or wall: Some buildings may settle so uniformly that the entire building moves down without producing cracking in the building's foundation or walls. For example, while it has a few settlement cracks, the Empress Hotel in Victoria BC, a very large masonry structure built on pilings on what was originally a marsh, has settled rather uniformly down over many decades, so that now visitors enter the hotel's "lobby" on what was originally its second floor.

Vertical Crack Patterns Caused by Vertical Foundation Wall Movement

Vertical movement between different sections of a masonry foundation wall, whether it is constructed of concrete, concrete block, brick, or stone, tends to produce vertical cracks or a combination of vertical and step cracks through the wall, though there are definitely exceptions to this rule, as we will point out.

Other vertical or near vertical cracks in poured concrete can occur in a masonry block or concrete or brick or stone foundation wall without leaning or bulging if the entire wall is moving due to footing settlement or frost. In this photograph notice that the cracking is occurring at a building corner, probably at a garage door. The footings at garages are often not buried as deeply as other portions of a home (which has a basement much deeper below grade). There is greater risk that the builder didn't get the garage footers below the frost line or that in addition, the un-heated garage is more vulnerable to frost damage (only in freezing climates of course).

Uniform Width vs. Tapered Width Foundation Cracks

We like to look at variations in the width of a vertical crack to try to understand further what's happening to the foundation wall. In general we pose that if a crack is wider at its top than its bottom, differential settlement may be allowing one section of the wall to slope downwards away from its neighbor. Or in less common cases, for example a footing which was placed mostly on soft fill but which passes over a boulder, might break over the boulder and slope downwards on both sides of the boulder, producing a crack wider at its top than its bottom. If a vertical crack is fairly uniform in width we pose that it was produced either by a non-sloping vertical settlement of one section of the footing or foundation wall, or the crack was produced by shrinkage (in some wall materials like concrete) not by vertical movement at all.

But unfortunately this "rule" has exceptions. When a masonry wall is "shrinking" such as curing concrete (and some experts pose also drying concrete block), it is not held uniformly in place across its length. The top of a poured concrete wall is generally unrestrained during the first portion of it's initial 28 days of curing, since nothing has been built atop the wall, or even if someone has started floor framing, the floor framing system does not secure the top of the wall against shrinkage movement. On the other hand, the bottom of the wall is pinned (or should be) to its previously poured and cured footing. The bottom of the newly poured concrete wall is more secured against horizontal movment along its length than its top. This might therefore produce some vertical shrinkage cracks that are wider at top than bottom. Why don't we always see this in concrete walls? As a concrete wall shrinks, the stresses produced in the wall are not concentrated at one single point, say the center of the wall; rather, shrinkage cracks may appear in various locations in the wall, not just at its center. Shrinkage cracks may be distributed rather than concentrated. However shrinkage cracks do tend to appear at local stress points in a wall such as at discontinuities in its form caused by windows, doors, or holes left for mechanicals and pipes.

We discuss the types of crack or movement patterns produced by shrinkage, expansion, and settlement further at SHRINKAGE vs EXPANSION vs SETTLEMENT.

Diagonal Cracks in Poured Concrete Foundations

Concrete walls tend to display vertical cracks but settlement or frost heaving at a corner of a concrete wall can produce diagnoal cracksor breaks in that location. Steep diagonal cracks may also appear in concrete foundations due to unusual point loads that exceed the compressive strength of the concrete (maybe it was weak concrete not high loading), and we've seen steep diagonal cracks in poured concrete and other high-rise masonry buildings exposed to frost damage. But in this photograph of a diagonal crack in a poured concrete foundation, we may be looking at a large shrinkage crack. Notice that discontinuity in the crack pattern?

Diagonal Step Cracking in Concrete block or Brick Walls Caused by Vertical Movement

FoundatCollapse400DJFss.jpg Vertical movement in a concrete block or brick wall might appear as either vertical cracks but more often as step cracks in which the crack pattern follows the mortar joints between the masonry units in a stair stepping pattern. In this photograph, major vertical dislocation, foundation settlement, has caused large step-cracking in the concrete block foundation wall. In addition to diagnosing and correcting the reason for this settlement or foundation movement, this section of wall will probably have to be rebuilt. Where step cracks are present, if you draw an imaginary line at right angles (orthogonal) to the diagonal formed by the stairstepped cracking, the downwards direction of the line will generally point to the center of the point of downwards (or up and down) movement in the structure. But unfortunately even this "rule" has exceptions. In Florida we observed a concrete block home with step cracking high in some of its walls. The cracks were traced to settlement at the other end of the building which was responding to soil subsidence over a sinkhole.

Leaning or Tipping Buildings

Some buldings may settle so that the entire building becomes visibly tipped or leaned to one side. Most structural problems can be avoided by proper design and planning; but structural failures have been common for a long time, and sometimes are costly to handle properly. This photo of the leaning tower of Pisa is by Tom Smith. Smith points out that the problems with the Tower have been known for generations and were evident even during its construction. The upper level of the tower was constructed with an offset to try to re-balance the structure. Modern reinforcement has permitted removal of cables that used to be tied to the tower of Pisa.

We distinguish between a leaning building and a leaning foundation wall (discussed below under horizontal movement). Although a tipped or leaning building obviously has leaning walls, they are all moving more or less together. Perhps settlement or frost heaves or expansive clay soils under a building resting on a strongly reinforced monolithich slab might tip without any cracking occurring in the building or its walls.

For a detailed discussion of the diagnosis of specific crack patterns caused by wall bulging and leaning in masonry foundations, and see FOUNDATION BULGE or LEAN MEASUREMENTS

Horizontal Movement in Foundations & Masonry Building Walls

Horizontal movement in building foundations or walls is generally caused by an external lateral or "sideways" force applied to some portion of the wall. Depending on the construction materials used and the strength of a foundation wall, a force applied to the wall can cause it to move in any of several ways:

• Bulging foundation wall movement: the wall may bend or "bulge", tending to bulge away from the force (usually inwards into the building from earth, water, or frost pressure), with the greatest amount of inwards movement at or near the point of greatest pressure or force being applied. If the wall is constructed of concrete block, for example, it may bulge inwards and crack or break horizontally along its mortar joints high on the wall if the damage is due to pressure from a heavy vehicle driving close to the wall, or it may crack in the top 1/3 of the wall if the damage is due to pressure from frost. Heavy or heavy and wet soils may also produce inwards movement and crackng lower on a wall when pressure is primarily due to earth pressure rather than frost. Of course the height of such bending or cracking depends on the height of the entire wall, how much of the wall is below ground level, and where the force is being applied.
• Leaning foundation wall movement: the wall may lean away from the force being applied (usually into the building from the same forces listed above). A reinforced concrete wall or a vertically-reinforced concrete block wall may tend to lean rather than break in response to the same forces we've listed. When force is closer to the top of such a wall, the top will lean inwards. When the forces are closer to or greatest at the bottom of the wall, the bottom may tend to lean inwards and the top of the wall lean "outwards".
• Shifting or creeping foundation wall movement: a foundation wall, or portions of it, may remain close to vertical, without leaning or bulging, but forces applied to the wall may cause the entire wall (or a portin of it) to move horizontally. We see horizontal shift or creep occuring in several cases: The wall may be sliding off of its footing, or an entire footing and wall may be sliding downhill over rock or clay soils; in this case vertical cracks may appear where the moving wall is or was joined to its neighboring side walls. Forces applied to a wall may cause a portion of it to break and slide horizontally over another portion. For example a masonry wall may become pushed inwards from soil or frost, but where the first course of blocks is held in place by a concrete floor slab, that course may remain un-moving. Depending on where the wall breaks from outside forces, upper courses of the masonry block wall will slide horizontally over and "hang over" the lower course(s) of block.
• Complex foundation wall movement: most of the drawings we see at seminars on foundation damage or used by companies offering foundation repair products are clear and helpful for understanding the concept of foundation damage and movement, but often they do not describe what we actually find in the field. Very often the forces that are causing a building foundation to move will cause a combination of bulging, cracking, leaning, and shifting of foundation or wall components.

We illustrate horizontal foundation wall movement patterns below.

Bulging or Leaning and Sliding Horizontal Wall Movement - Masonry Block "Overhang"

Inspectors or building owners may also 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. This is a photograph of frost push and horizontal overhang or sliding between horizontal courses of a masonry block wall.

Impact Damage to Foundation Walls - horizontal movement

Impact damage from a vehicle or from unusual weather such as a hurricane which lifts and tosses large objects, can lead to severe foundation or masonry wall damage and may even render the wall unstable and unsafe. In the photograph shown here the cause of damage to the foundation wall is pretty obvious. Almost certainly a delivery truck has backed into this concrete block wall, perhaps even more than once. The damage to this wall was extensive, extending nearly to the top of the structure. The wall needs extensive repairs, probably reconstruction.

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 the photograph here we suspect that the cracks in this masonry block wall occurred as a defective wall footing began to creep down a steep hill behind the building. In a pure example of horizontal creep or movement without leaning in a masonry wall or foundation, 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. Other vertical or near vertical cracks in concrete block can occur in foundation wall without leaning or bulging if the entire wall is moving due to footing settlement or frost or, as we showed here, possible tipping or leaning of the footing itself. If the bottom of a wall is not pinned in place by a secure footing or a concrete slab, or if the entire footing itself begins to move, the entire wall, from top to bottom may move horizontally with no leaning and with no "overhang" of one portion of the wall over another. In this case we'd expect to see cracking or evidence of separation of this section of wall from its neighboring sides - as you can see in the upper vertical cracking at the left side of the masonry block wall in the photograph above.

Horizontal wall movement and step cracking in brick walls due to thermal expansion

Horizontal movement occurs in brick masonry walls due to thermal expansion, producing step cracking and potentially also verticl cracks through structural brick or brick veneer walls. If you are considering a brick masonry building, or a building carrying a brick veneer exterior, we discuss and illustrate thermal cracking in brick masonry in detail at Thermal Expansion Cracking of Brick Also see See SHRINKAGE vs EXPANSION vs SETTLEMENT for aid in distinguishing between these different conditions.

Combinations of Foundation Wall Movement, Horizontal & Vertical Crack Patterns Occuring Together

Wall bulge and step cracking

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.

Combinations of Foundation Wall Movement During Collapse

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.)

Combinations of Building Foundation Movement due to Earthquake, Flood, or Storm Damage

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 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./P>

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.

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.

Examples of other step cracks occurring in masonry walls or masonry foundations

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.

How to distinguish between a "bulged" foundation wall and a "leaning" foundation wall, and why we care

Why distinguish between leaning and bulging foundation walls?

We care about the distinction between leaning and bulging because understanding the location and pattern of foundation wall cracking or movement may help us diagnose its cause and thus may help us understand what actions are needed to stop further foundation movement or perhaps to decide on a course of repair or reinforcement of the wall. For example, recognizing that a foundation wall has bulged inwards at about the depth of the frost line at a building may tell us that the root cause of that particular foundation movement was frost pressure from spillage of roof runoff too close to and along the building wall.

The same forces produce different effects on poured concrete walls compared with masonry block, brick, or stone walls

Even a concrete wall which is bulged is likely 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. It's more likely that a reinforced concrete wall will be caused to lean or to shift horizontally while a masonry unit wall or stone wall is likely to be bulged and cracked by the same external forces.

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.

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). Watch out, in some cases a foundation wall may not lean in the direction you expect. For example a reinforced masonry block wall or poured concrete wall which has been pushed inwards by earth loading might move inwards at the bottom of the wall rather than at the top. The bottom of the wall will have been pushed in to the building basement or crawl space and the top may actually begin to lean out and may even become visible outside, protruding out past the building framed wall. (Earthquake damage which shifts a building off of its foundation can also produce something that looks like and can be mistaken for this condition.)

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Technical Content Reviewers

for Foundation Crack and Movement Damage Evaluation, Diagnosis, & Reporting

• Daniel Friedman - ASHI (1986-2006) - author of this website and article, building failures researcher.
• 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
• Dave Wickersheimer, P.E. R.A. - IL*
• *These reviewers have not returned comment 6/95

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