Masonry structure crack types:

This chapter of the "Foundation Crack Bible" discusses in detail the process of distinguishing types foundation damage due to shrinkage, expansion, or settlement, for all types of masonry foundations: concrete, masonry block, wood, stone, pre-cast.

Foundation cracks and movement are discussed by type and location of foundation cracks, vertical foundation cracks, horizontal cracks, and diagonal foundation cracks, and shrinkage cracking.

Foundation cracks, which are signs of foundation damage, can mean very different things depending on the material from which a foundation is made, the location, size, and shape of the foundation crack, and other site observations.

Types of Masonry Cracks: Distinguish Shrinkage, Expansion, and Settlement

General Comments about foundation expansion or shrinkage

Our page top photo shows severe cracking in a newly set concrete foundation. Our reader-contributed photo shown here illustrates complex cracking, probably from frost heaves and settlement, in a foundation that uses a combination of dissimilar masonry materials: stone, concrete, and brick.

All three components are damaged.

[Click to enlarge any image]

Cracks will occur in masonry structures: Most solid materials may both expand and contract in response to temperature variations.

Solid materials may be cracked by pressure from loading.

Brick structures expand. In masonry foundations, bricks actually expand indefinitely, though probably at a decreasing rate. A long brick wall exposed to sunlight and cold weather and built without expansion joints will crack and fail.

Concrete block walls shrink but don't normally expand (below grade).

Masonry blocks may shrink and expand.

Poured concrete shrinks after pouring. Poured concrete shrinks during curing but may also expand or contract in response to moisture.

All of these materials respond to changes in moisture and temperature.

Determining when action is needed: All cracks need to be separated into those which are expected to require no further repair except possibly cosmetic (which can help future monitoring), those which merit ongoing monitoring for change and possibly signs of worsening conditions, and those which are so significant as to require repair.

Setting priority of action: Repair work needs to be identified with respect to urgency, ranging from immediate (risk of collapse or other unsafe conditions) and less urgent.

To the extent that the inspector can see the extent of movement and the potential for damage to a building, and to the extent that the inspector can make a reasonably confident guess about the cause of foundation damage or movement, s/he can estimate the chances of its continuance and thus help set a priority for further evaluation or repair, as well as setting the specifics of outside repairs to reduce further damage such as keeping water or vehicles away from the building.

Article Contents

• SHRINKAGE vs EXPANSION vs SETTLEMENT
  • FOUNDATION SHRINKAGE - evidence, crack patterns, other evidence
  • FOUNDATION EXPANSION - evidence, crack patterns, other signs
  • FOUNDATION SETTLEMENT - evidence, crack patterns, other indications

Evidence of Foundation Shrinkage

A variety of site conditions can lead to cracks in a concrete or other masonry foundation walls or floor slabs.

Speaking generally, foundations may be damaged and cracks may appear from innocent causes unlikely to affect the structure such as concrete shrinkage cracks, initial settlement, or from potentially more serious causes such as ongoing settlement, unusual pressures or loading, or from improper construction.

Identification of Shrinkage Cracks in Poured Concrete Foundations or Slabs

Shrinkage cracks in poured concrete are easily recognizable and can be distinguished from other types of cracks that occur later in the life of a foundation wall or floor slab.

Concrete shrinks as a natural process during its curing. You can see the shrinkage of even a perfect concrete floor slab with no visible cracks in its surface if it was poured inside of an existing foundation.

Notice the gap between the edges of the slab and the foundation wall? Notice the stains or concrete debris on the wall at the slab level? These indicate that at the time the slab was poured it was touching the wall. A poured concrete wall shrinks as well.

Concrete curing is a chemical reaction, not just "drying" or loss of water. But depending on the concrete mix, amount of water, portland, aggregate type, temperatures, humidity, groundwater, sun exposure, groundwater, and other conditions, the amount of shrinkage that will occur in concrete as it cures varies.

In any case, this concrete shrinkage process causes the concrete to develop internal stresses.

To relieve those stresses, unless control joints were included in the wall or floor slab design, the wall or floor is likely to crack in a classic "concrete shrinkage pattern" as the concrete cures.

Cracks in a poured concrete foundation which are diagonal or vertical and which are generally uniform in width, or which taper to an irregular hairline form and stop entirely, which are usually discontinuous in the crack's finest or hairline area (the crack "stops and starts" in the same area), are usually shrinkage cracks and should not be ongoing nor of structural significance, though they may invite water entry through the wall.

[See our article on POLYURETHANE FOAM INJECTION CRACK REPAIRS]

Shrinkage cracks in concrete range in length from a few inches to the entire height of the concrete wall, extending from wall top to bottom.

Concrete shrinkage cracks virtually always extend through the full thickness of the foundation wall, which means they can provide a ready path for water entry into the building.

Common areas for a shrinkage concrete crack to develop are under a basement window, above a doorway in the middle of a long wall or where the foundation "steps down." Shrinkage cracks also often occur near the middle of a large poured concrete wall [or floor] if no control joints were used. [Concrete control joints are very often omitted in residential construction.

Shrinkage cracks and how to recognize and diagnose them are discussed further

at

• CONCRETE SHRINKAGE CRACKS
• SETTLEMENT vs. SHRINKAGE CRACKS
• SHRINKAGE CRACKS at FOUNDATION WALLS

Evidence of Foundation Expansion

Brick, in particular, whether used in a foundation or as a building wall, expands over time and as moisture, temperature, and other conditions vary. Dave Wickersheimer, P.E. and R.A., who is a masonry failures expert from the SHC, informs us that brick "grows" or expands indefinitely.

However if we exclude heating effects of sun exposure (discussed below), most brick expansion from its internal chemistry probably occurs early in its life.

Thermal expansion of brick: Thermal expansion cracks in brick are often nearly vertical, maybe passing right through the bricks not just at the mortar joints, and tend to be near the building corners.

In any long brick wall, whether it's veneer or structural, if it's real brick, look for expansion cracks if the wall design did not include vertical expansion joints. Southern exposure, walls exposed to more sun, take more heat and may show more expansion due to the added thermal effects of sunshine.

Although it's natural state causes brick to expand or "grow" slowly in size continuously, more often, brick walls exposed above-grade are subject to more rapid and more significant heating gains from sunlight.

These brick walls may expand (when heated) and contract (when cooled) sufficiently to cause major damage if proper control joints are not used during construction. If you observe long expanses of brick masonry walls above grade and without expansion joints, look for expansion cracking. When caused by thermal expansion, brick walls may show most movement at the two ends of the wall most-exposed to sunlight.

The author, using a simple plumb line and measuring tape, has measured as much as 4" of expansion found at the top of a brick structure whose wall corners leaned out 4" over the wall bottom from this force over the height of a two story structural brick wall.

Brick masonry walls below-grade are of course not exposed to heating and expansion from sunlight, but instead are exposed to earth pressure (look for horizontal cracking), moisture gain, and in freezing climates, frost damage too.

Look for horizontal cracks in brick walls at or near the frost line, and look for stair-stepped cracks at corners of the building from frost heave or settlement.

We discuss and illustrate thermal expansion of brick walls in detail

at THERMAL EXPANSION CRACKS in BRICK.

Foundation Settlement: crack patterns, other evidence

The photograph shows a significant settlement crack in a poured concrete foundation of a new (modular) home. This crack appeared first as a fine hairline crack. The owner monitored the crack as it expanded to a significant width over the ensuing year.

A combination of poor site preparation of soils below the building footings (un compacted fill), portions of footings sitting on bedrock, and nearby blasting led to differential settlement that produced this damage. We suspected that also some reinforcing steel may have been omitted from construction of the foundation wall.

A settlement crack is more likely to be wider at top than its bottom as the foundation "bends" over a single point (oras one section of footing tips downward from its neighbor), allowing differential settlement; it is possible for a settlement crack to appear fairly uniform however if a foundation breaks vertically and then pursues differential settlement.

Settlement cracks need to be separated into initial settlement due to construction or site factors and ongoing settlement due to site factors.

Settlement cracks are usually wider at the top of the crack, usually continuous, and may occur multiple times in a wall

• Direction of downwards movement: If you draw an imaginary line orthogonal (at a right angle to) the line of a diagonal foundation crack, usually the line you've drawn points to the direction of downwards movement in the wall.
  
  However a diagonal crack may also indicate upwards wall-lift such as by frost or expansive clay soils which are more active under one portion of a foundation wall than another.
• Sink holes and foundation cracking: Settlement cracks may appear at the opposite end of a wall when a reinforced masonry foundation is settling due to presence of a sinkhole (for example in Florida).
  
  In this case the diagonal crack can fool the inspector if s/he looks for downwards movement at the corner closest to the crack. Instead, the main portion of the building can be sinking! This condition can be distinguished by observing or measuring the directions of floor or wall slope.
• Multiple settlement cracks in walls: Multiple cracks of either type (settlement or lifting) may occur in a given area.
  
  Usually settlement cracks are visible both outside and inside of the foundation wall if the wall material is exposed to view at all.

Watch out: 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. [The photograph shows severe foundation damage discovered during construction of a new home.]

Basic Research on Types of Foundation Cracks

Research on Types of Cracks in Masonry Structures: Shrinkage, Expansion, Concrete, Concrete Block, Brick, Stone Foundations, Walls, Shear Walls

• Also seeReferences or Citations below
• Matsumura, Akira. "SHEAR STRENGTH of REINFORCED MASONRY WALLS" [PDF] In Proc., 9th World Conf. on Earthquake Engineering, vol. 7, pp. 121-126. 1988.
• Minaie, E., M. Mota, F. L. Moon, and A. A. Hamid. "In-plane behavior of partially grouted reinforced concrete masonry shear walls." Journal of Structural Engineering 136, no. 9 (2010): 1089-1097.
• NCMA, CRACK CONTROL IN CONCRETE MASONRY WALLS [PDF] TEK 10-1A Movement Control (2005), National Concrete Masonry Association, 13750 Sunrise Valley Drive, Herndon, Virginia 20171-4662 USA Website: www.ncma.org
  source: AIA Continuing Education Series, http://alconcrete.org/wp-content/downloads/cworks-presentation-lee.pdf
  Excerpt:
  
  Cracks in buildings and building materials normally result from restrained movement.
  
  This movement may originate within the material, as with volume changes due to moisture loss or aquisition, temperature expansion or contraction, or may result from movements of adjacent or supporting materials, such as deflection of beams or slabs.
  
  In many cases, movement is inevitable and must be accommodated or controlled.
• NCMA, MAINTENANCE of CONCRETE MASONRY WALLS [PDF] (2004) TEK 8-1A National Concrete Masonry Association, 13750 Sunrise Valley Drive, Herndon, Virginia 20171-4662 USA Website: www.ncma.org retrieved 2018/08/06, original source: http://www.ncma-br.org/pdfs/5/TEK%2008-01A.pdf
  
  Excerpt: Once placed in a structure, concrete masonry units are subject to a variety of forces and stresses which, besides structural loads, include shrinkage stresses due to drying, temperature fluctuations, and carbonation (an irreversible reactionwith carbon dioxide in the atmosphere).
  
  Although the net resulting shrinkage in a finished structure can vary considerably (for example, temperature movements can vary greatly with exposure and unit color, while drying shrinkage can be expected to be higher for units having a higher cement content), the combined effect of these shrinkage components could be sufficient to cause large tensile cracks in the masonry if proper precautions are not taken. Shrinkage cracking and crack control strategies are covered in more detail in TEK 10-1A, TEK 10-2B, and TEK 10-3 (ref. 1, 2, and 3).
  
  The next leading cause of cracking in concrete masonry walls is differential settlement due to uneven support of the foundation. Due to the highly complicated and problematic nature of such cracks, the reader is encouraged to seek the aid of a qualified design professional for recommendation on corrective actions for differential settlement.
• NCMA CRACK CONTROL INCONCRETE MASONRY WALLS [PDF] TEK 10-1A (2005) https://www.coursehero.com/file/16714458/10-1A/
  
  Excerpt from Introduction:
  Cracks in buildings and building materials normally result from restrained movement. This movement may originate within the material, as with volume changes due to moisture loss or aquisition, temperature expansion or contraction, or may result from movements of adjacent or supporting materials, such as deflection of beams or slabs.
  
  In many cases, movement is inevitable and must be accommodated or controlled. Designing for effective crack control requires an understanding of the sources of stress which may cause cracking.
  
  The article describes the following types of masonry cracking and cracking forces:
  
  1. Shrinkage / restraint cracks
  
  2. Differential movement cracks
  
  3. Excssive deflection cracks (typically settlement)
  
  4. Structural overload (shear loads, step cracking, or horizontal load, buckling bending cracks)
  
  5. Differential settlement ( see shear loads as the step cracking patterns may look similar)
  
  These crack types may occur in response to the following forces:
  
  1. Drying shrinkage [or wetting expansion]
  
  2. Temperature changes
  
  3. Carbonation
  
  4. Restraint [In my DF opinion this is a force that must combine with other forces to produce cracking] in respose to movement: differential, deflection, structural overload, settlement
  
• NCMA CONTROL JOINTS FOR CONCRETE MASONRY WALLS - EMPIRICAL METHOD [PDF] TEK 10-2C (2010) http://www.ncma-br.org/pdfs/38/TEK%2010-02C1.pdf
• NCMA CONCRETE BRICK & OTHER MASONRY VENEER CRACK CONTROL [PDF] TEK 10-4 (2001) http://www.ncma-br.org/pdfs/5/TEK%2010-04.pdf
  
  This article notes important differences between traditional clay-based brick construction and concrete-brick construction.
• NCMA, JOINT REINFORCEMENT FOR CONCRETE MASONRY TEK 12-B [PDF] (2005) https://masonryinfo.org/wp-content/uploads/2016/05/joint-reinforcement-for-concrete-masonry.original.pdf
• Shedid, Marwan T., Robert G. Drysdale, and Wael W. El-Dakhakhni. "Behavior of fully grouted reinforced concrete masonry shear walls failing in flexure: Experimental results." Journal of structural engineering 134, no. 11 (2008): 1754-1767.
  
  Abstract: In this paper, the possibility of achieving a high level of ductility by flexural yielding in fully grouted reinforced concrete masonry shear walls is evaluated. Six full-scale walls were tested to failure under reversed cyclic lateral loading to investigate the effects of amount and distribution of vertical reinforcement and the level of axial compressive stress on the inelastic behavior and ductility.
  
  Results showed that yielding of the outermost vertical bars extended to a height equivalent to half the wall length. Also, the top wall displacement (drift) at the onset of yielding of the vertical reinforcement was highly dependent on the amount of reinforcement, but only minimally affected by the level of axial compressive load. However, at maximum loads, the displacements were less sensitive to either the amount of vertical reinforcement or the level of axial compression.
  
  Correspondingly, the displacement ductility was found to be very sensitive to the amount of vertical reinforcement, but was not dependent on the level of axial compression. In general, high levels of ductility and energy dissipation capabilities accompanied by relatively small strength degradation were observed for the test specimens.
  
  Excerpt: the outermost grout columns, which were almost intact except for some vertical cracks Fig … With increased displacement, spalling of the face shell and grout cracking became more significant at the … Widening of the vertical crack in the grout column coincided with initial buckling …

...

Continue reading at FOUNDATION DAMAGE SEVERITY or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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• FOUNDATION CRACKS & DAMAGE GUIDE - home
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• FOUNDATION REPAIR METHODS for our catalog of Foundation Repair Methods - Examples of Typical Foundation Repairs for various types of foundation cracks, leaks, settlement, movement, or other failures
• POLYURETHANE FOAM INJECTION CRACK REPAIRS for details of the procedure for using polyurethane foam to seal foundation cracks.
• SEAL CONCRETE CRACKS, HOW TO

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