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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
Guide to evaluating foundation cracks in buildings: 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. If you don't see information you want, ask us for it using the comments box on this page. This foundation crack diagnosis and repair article serie3s discusses in detail the process of evaluating foundation cracks and signs of foundation damage by examining the crack size, shape, pattern, and location. 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.
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.
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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. The size, shape, pattern, location of foundation cracks on a building, along with correlation with other site and construction conditions helps distinguish among probable causes.
Strategy for Building Foundation or Floor or Slab Crack, Damage, or Movement Assessment
To understand the cause, effect, and remedy for all types of building foundation or masonry wall damage or movement we have categorized foundation damage into these broad categories:
General Suggestions for the Evaluation of Foundation Cracks
By knowing the probable cause and history of foundation cracking or movement one can distinguish between continuing movement (more likely to be a problem) and single events which may, depending on extent of damage, not require repair. This chapter elaborates types and patterns of foundation cracks to assist in that evaluation.
Look at shape, pattern, frequency of occurrence, relationship to wall discontinuities and angles, placement of wall penetrations, correlation with cracks in floors, and location in the wall (corners, center), as well as length, width, continuity, age of wall, relation to site conditions (depth of backfill, blasting, rock).
Shrinkage cracks are usually uniform in width or (less common) vee-shaped, wider at top and diminishing or stopping before reaching the bottom of the foundation wall (where attachment to footing may tend to hold foundation wall materials in place). A wall crack which continues into the floor is likely to involve the building footings and may be a settlement crack of more structural importance.
Concrete shrinks as it cures. In poured concrete, shrinkage cracks may be non-uniform if wall components are held by footings/framing; very often there are minor shrinkage cracks which are hairline, random, intermittent, multiple, and meandering in the concrete, forming discontinuous cracks in the wall. Shrinkage cracks occur as concrete cures, appearing more frequently and larger if the mix was improper and where control joints were omitted. Omission or pattern of placement of steel reinforcement may also be a factor in crack formation and location.
Poured concrete shrinkage cracks: usually shrinkage cracking is due to conditions at original construction: poor mix, rapid curing, possibly other conditions. Shrinkage cracks are less likely to require structural monitoring and repair in poured concrete as they would be expected to continue after initial curing.
Concrete block foundation walls shrink as they cure. They rarely expand much on exposure to moisture and temperature variations. In concrete block walls shrinkage cracks are likely to be uniform in width and usually occur towards the center of a concrete masonry unit (CMU) wall. The wall is stronger at the building corners.
Brick walls do not normally shrink, but rather, grow indefinitely. Bricks are not often used for below-grade foundations but were often used above-grade supporting the first floor of older buildings, and of course entire buildings may be constructed using structural brick walls (look for the bond courses). If you see a crack in a brick wall it's more likely due to movement in the structure, a support problem, or due to thermal expansion. Cracks in structural brick walls may be very serious if the bond courses are broken as there is then a risk of sudden catastrophic wall collapse. Cracks and especially bulged cracked brick walls need immediate expert investigation.
Stone foundation walls do not normally crack through individual stones, but the interlaced stone layout of the wall may be bulged and cracked due to damage from frost, loading from driving vehicles near the wall, or by the removal of stones to pass piping or make doorways. As with other cases of foundation movement, a diagnosis of the cause, amount of movement, and effects on structure are needed to decide what repair may be needed.
In the photos shown here, substantive cracks appeared and continued to increase in size in this poured concrete foundation used to support a modular home which had recently been completed. The cracks and foundation movement were probably due to a combination of: poorly prepared foundation footings, blasting on an adjacent building lot to prepare that site for new construction, and possibly omission of steel reinforcement in the poured wall.
The cracks in this building foundation wall were visible shortly after construction as vertical hairline openings (less than 1/16" wide) in the right hand foundation wall, above grade and inside in the basement. Within a year the owner reported several times that the cracks were becoming noticeably wider.
A careful inspection of the building interior suggested that the front foundation wall and portions of the right foundation wall were settling. There were no corresponding cracks in the finished surfaces of the structure, probably because this was very stiffly-framed modular construction. Notwithstanding the absence of damage upstairs, this was a problem that deserved further evaluation and repairs. The builder may have repaired the foundation by supporting it from below using one of the methods described at FOUNDATION REPAIR METHODS.
Additional photographs of types of foundation cracks and other foundation damage: we have an extensive library of photographs which will be added to this document. Pending completion of that work, contact the author if assistance is required with images.
Note: vertical foundation cracks often appear in multiples multiple cracks in one or more area.
While a vertical foundation crack could be serious depending on its cause and on the type of foundation in which it appears (stone, brick, masonry block, concrete), these are often the least threat to the building. If there is significant vertical dislocation or signs of ongoing movement, further investigation is more urgent. If the cause is shrinkage (concrete, masonry block) it is probably less of a concern than if due to settlement. A vertical crack due to earth loading or frost would be unusual.
Clues to help diagnose the probable cause of diagonal foundation cracks in buildings:
Note that often at these foundation failures cracks are visible both outside and inside, but outside they may be covered by backfill.
For detecting evidence of sink holes in an area by visual inspection see Sink Holes: Can X-Ray Vision [Advanced Building & Building Site Inspection Techniques] Warn of Sink Holes? in Florida or elsewhere
These notes presume that you are examining a wall which is entirely or nearly all below-grade level.
Horizontal Foundation Cracks Located High on a Foundation Wall
Horizontal foundation cracks located in the upper third of a concrete block wall (presuming most of the wall is below grade) are most likely to have been caused by vehicle loading or in freezing climates, by surface and subsurface water combined with frost. In northern climates if we see cracked mortar joints in the top third of a block wall, at about the same depth as the frost line in that area the damage is almost certainly due to frost. Often outside we'll find corroborating evidence such as drip lines below the building eaves confirming a history of roof spillage against the building, and back inside we may see that the foundation damage is occurring only at the building walls below roof eaves and not at the gable ends of the home.
Horizontal Foundation Cracks Located at Mid-wall Height on a Foundation
Masonry block or stone walls which are cracked and/or bulging inwards at mid height on the wall are likely to have been damaged by vehicle traffic or earth loading.
Horizontal Foundation Cracks Located Low on a Foundation Wall
The forces exerted by soils against a foundation wall increase geometrically as we move from surface level of the soil against the wall to the areas near the bottom of the wall. In other words, earth pressure is greatest at the bottom of the wall. This fact helps us distinguish between frost or water-related cracking and simple earth loading in some cases since a wall which has become dislocated laterally only at or near its bottom is likely to have been damaged by earth loading.
Horizontal Cracks in an Attached Garage Foundation
Construction methods for attached garages (as opposed to a garage located under a home and adjoining its basement) may create some special opportunities for foundation cracks:
Where are Horizontal Foundation Cracks Visible?
Horizontal foundation cracks are usually visible only from inside a basement or crawl area unless building is all masonry.
Lateral or horizontal movement of a masonry foundation wall inwards from earth pressure will often be seen at the first mortar joint above a basement or crawl space slab. Remember that the slab itself may be holding the very first course of masonry blocks or brick in place. This is a useful detail to keep in mind if you are using a plumb line and measuring tape to document the total amount and location of wall movement. The bottom course of concrete blocks or bricks, held in place by the floor slab, can usually be taken as a baseline of zero movement, from which other measurements to the plumb line are compared over the height of the wall.
SHRINKAGE vs EXPANSION vs SETTLEMENT - Distinguishing Among Shrinkage, Expansion, and Settlement Cracks
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. In masonry foundations, bricks actually expand indefinitely, though probably at a decreasing rate. Poured concrete shrinks after pouring. Masonry blocks may shrink and expand. All of these materials respond to changes in moisture and temperature. 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). Poured concrete shrinks during curing but may also expand or contract in response to moisture.
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.
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 Using Polyurethane Foam for Foundation 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 SHRINKAGE vs EXPANSION vs SETTLEMENT.
Suggestions for Repairing Foundation Shrinkage Cracks
Before repairing a foundation crack by sealing it against water entry, it is important to diagnose the cause of the crack and its effects on the building structure.
When it has been determined that there is an underlying ongoing problem such as one leading to foundation movement or damage to the structure, the underlying problem should be corrected as part of any foundation or slab repair.
Cracks in poured concrete walls that are larger than 1/4", cracks which are increasing in size, or cracks which are otherwise indicative of foundation movement should be evaluated by a professional. The diagnosis and evaluation of foundation cracks and structural foundation damage and repair methods are discussed at FOUNDATION REPAIR METHODS
What to do about shrinkage cracks in foundations
Once any concrete cracks it is possible for water to leak into the building through the crack. There are several ways to repair a basement crack leak. An easy, quick, and effective measure to stop basement or crawl space water entry through a foundation crack is to perform an injection of polyurethane foam into the basement crack. [Also be sure to find and fix the sources of water outside.]
Water entry leaks at foundation cracks: Polyurethane foam sealant is used for foundation crack repairs to stop water entry. (Also find and correct outside water sources). See our article on Using Polyurethane Foam for Foundation Repairs.
Structural repairs as well as sealing against water entry may be attempted for cracked foundations using masonry epoxy products. These products may be used for repairing cracks in concrete foundations, possibly including structural repairs, following evaluation and advice from a foundation professional. An evaluation of the presence, absence, or condition of reinforcing steel in cracked concrete foundations should be a part of the inspection.
See our discussion of foundation repair methods at FOUNDATION REPAIR METHODS
Distinguishing of Other Types of Concrete Wall or Slab Cracks from Shrinkage Cracks
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: Brick walls exposed above-grade are subject to significant heating gains from sunlight and may expand and contract sufficient 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. [Note: POK JCC file-DJF].
Brick 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), and in freezing climates frost damage (look for horizontal cracks in walls at or near the frost line, and look for stair-stepped cracks at corners of the building.
Brick cracking due to thermal expansion is discussed and illustrated in detail at Thermal Expansion Cracking of Brick
A settlement crack is more likely to be wider at top than its bottom as the foundation "bends" over a single point, 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.
Usually wider at top, usually continuous, may be multiple!
See this close companion article: FOUNDATION FAILURES by TYPE & MATERIAL which describes the types of foundation damage, cracks, leaks, or other defects associated with each type of foundation material (concrete, brick, stone, concrete block, etc.).
Frequently Asked Questions (FAQs) about the occurrence of cracks in building foundations or in building masonry walls: how to inspect, understand & evaluate foundation crack patterns
Questions & answers or comments about the cause and repair of all types of building foundation and floor slab cracks.
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