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Concrete Wall Cracks and What They Mean

What does that crack in my basement mean? Is my house or foundation in danger? Do I have a structural problem? Or are foundation cracks common and expected?

Concrete foundations crack when a tremendous amount of forces are built up against the foundation wall and the force exceeds the strength of the concrete. In order to repair a cracked concrete foundation, understanding the characteristics of the concrete foundation cracks help identify what caused the cracks to occur. Some of these types of cracks are of little worrisome by themselves and after having a certified technician permanently repair the cracks, you can have peace of mind.

Types of Concrete Cracks

 
Shrinkage/Temperature
SettlementStructural
ShapeDiagonal or Vertical V-Shape
(less common)
DiagonalNearly Horizontal
WidthUniform in width, or taper to an irregular hairline form or stops entirelyLarger in width on top and diminishing as it reaches the bottom)Wider on top than the bottom as the foundation "bends" over a single pointCrack tends to get wider over time
HeightFew inches to the entire height of the concrete wall (from wall top to bottom)VariesVariesVaries
Period of time crack appearsWithin the first 28 days from when the foundation wall or floor is poured Within the first 28 days from when the foundation wall or floor is pouredAny period of time during the life of the foundationCrack may appear as early as the first month of concrete being poured. Over time, the crack gets wider, indicating a structural problem.
Example LocationsUnder a basement window, pocket beam, step down, or other openingsCrack develops over the area where subgrade was unevenCrack appears 16" to 48" from the top of the wall.

More common in block foundation walls.
OutcomePossible water or moisture seepageStructural foundation problem.

Instability of your home.
Structural RiskNo structural concern; however, crack should not be ongoing or have significant lateral displacementIf crack reaches the bottom, potential damage to footing and possible structural foundation problemNo structural concern. This type of crack may appear more than once in a wall.Yes. Structural engineer inspection recommended.
Possible Reasons of Crack DevelopmentAs the concrete cures, concrete shrinks and develops internal stresses within the concrete wall or slab. This shrinkage is likely to cause the concrete to crack. Subsoil is inconstant or underlying ground has not been compacted or prepared properly.

Footing settlement, absence of or poorly poured footing or movement of footing.
Horizontal loading or settlement.

Applied load (hydrostatic pressure or operating heavy equipment around foundation wall)
Preventative MeasuresInstall appropriate cold joints during initial constructionConcrete foundation be poured over properly compacted soil or ground
Solution for Crack RepairInject SEAL 3003 Flexible ResinA qualified structural engineer should be consultedInject SEAL 3004 Flexible ResinInject SEAL 5000 Epoxy Resin if the crack is superficial. Otherwise, a qualified structural engineer should be consulted.
Hairline Cracks

These cracks may develop in concrete during the curing stage. If the cracks appear within the first 28 days of pouring the concrete foundation, concrete may have been poured too quickly or improperly mixed. Hairline cracks are not considered a risk for foundation stability; however, they do allow moisture, water leakage and radon gas.  Hairline cracks usually appear in the center of walls because the corners of walls have more stability.

SOLUTION

SEAL 4003 Hairline Crack Injection Resin can be used to completely fill the cracks to keep water, moisture, or unwanted insects from entering your basement.

Vertical Cracks

Types of vertical cracks – How to diagnose the significance.

Type of foundationCharacteristicsCause of Crack Risk
Poured Concrete Wall- Nearly straight or wondering
- Generally even in width
- Intermittent
Shrinkage/ThermalLow risk
Two Joint Masonry Structures
- Cracks in masonry wall between two structures such as an add-on garage that is built on more shallow footings on top of backfill next to the full foundation.Differential settlement
Thermal movement
Moderate risk
Masonry Block Wall- Straight
- Generally even in width
- Crack in mortar joints
- Possible crack through concrete block
Shrinkage/ThermalLow to moderate risk
Brick Wall- Straight or stepped, especially near ends of wallExpansion/ThermalCollapse Risk
(if wall bond courses are broken)
Masonry Block Wall- Crack in foundation wall is wider on bottom than topSettlement under buildingModerate risk
(less risk than a horizontal crack)
Brick Wall- Crack in foundation wall is wider on bottom than topSettlement under buildingCollapse Risk
(if wall bond courses are broken)
Foundation Wall- Uniform in width
- One side of crack/wall higher than the other
Differential settlement in footingsPossible serious defect
These cracks are often found in multiples in one or more area.

 

Vertical cracks are considered to be the least threat to the building, even though depending on the cause of the crack and type of foundation (concrete, masonry block, brick or stone), these cracks could be serious. If the cracks show significant vertical dislocation or displacement, a qualified structural engineer should be consulted for further investigation.  It is less of a concern if the cause is due to shrinkage (concrete or masonry block) than if due to settlement.  

SOLUTION

Concrete Crack Injection: SEAL 3000 series flexible crack injection resins can be used to completely fill the cracks to keep water, moisture, or unwanted insects from entering your basement.

Structural Problem: A qualified structural engineer should be consulted.

Horizontal Cracks

These are cracks found horizontally across the center of the wall and are usually caused by an applied load such as earth compacting as it settles, hydrostatic pressure due to high water table or poor drainage, backfilling too soon or improperly around foundation walls, or operating heavy equipment too close to foundation wall. Frost damage can also cause horizontal cracks in foundation walls and are commonly found near the top of the foundation wall. If there are any signs of horizontal foundation wall movement such as bulging, leaning or tipping foundation walls or even the movement of the entire foundation wall, a qualified structural engineer should be consulted.

SOLUTION

Concrete Crack Injection: SEAL 3000 series flexible crack injection resins can be used to completely fill the cracks to keep water, moisture, or unwanted insects from entering your basement.

Structural Problem: A qualified structural engineer should be consulted.

Diagonal cracks

Types of diagonal cracks – Typical Patterns in Concrete Foundation Walls

Location of CrackCharacteristicsCause of Crack
Foundation Wall
(Anywhere)
- Wider at bottom than top- Settlement Under Building
Under a Ground Floor Window- Starting from sill to ground
- Sill bowed up
- Foundation Heave
- Clay Soil
- Frost
- Shallow or Absent Footing
Corner Towards Adjacent Opening- Wider at top than bottom- Foundation Settlement
- Expansion Clay Soil
- Frost Damage
- Damage From Nearby Tree/Shrub
Corners of Foundation Walls – In Cold Climates- Step crack/diagonal crack- Insufficient Footings
- Shallow Footings
- Frost Heave or Frost Lensing
Corner of Windows or Other Openings- Emanates from the corner of the window or opening (known as Reentrant Cracks)- Stress built-up at the corner

Furthermore, diagonal cracks that are even in width are sometimes caused by shrinkage and will only cause water leakage or radon entry.  Diagonal cracks that extend the full height of the foundation wall are usually caused by settlement. Settlement cracks that are a result of a problem in the footing on one side of the wall can also cause a diagonal crack.  In this case, a certified structural engineer should be consulted.   

SOLUTION

Concrete Crack Injection: SEAL 3000 series flexible crack injection resins can be used to completely fill the cracks to keep water, moisture, or unwanted insects from entering your basement.

Structural Problem: A qualified structural engineer should be consulted.

To learn more about our premium services and capabilities or to schedule for a Free, No Obligation, In Home Estimate, please give us a call today at 1-888-768-7765 or complete our online form. We are happy to help you determine the best solution to completely solve your basement waterproofing needs.
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