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• How to Inspect & Diagnose Concrete Block Foundation Cracks, Leans, Bows, Settlement - Masonry block or "cinder block" foundation defects listed, described & explained
• Concrete block or "cinderblock" or concrete masonry unit (CMU) foundation inspection procedures are provided.
• Photographs of foundation damage patterns and types

Here we discuss Concrete block or "cinder block" or concrete masonry unit (CMU) foundation inspection procedures and the diagnosis of cracks, bulges, leaning, bowing, and settlement in concrete block foundations and building walls such as damage due to impact, settlement, frost or water damage, and other causes.

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. Also see this close companion article: FOUNDATION CRACK EVALUATION which discusses in detail the process of evaluating foundation cracks and signs of foundation damage by examining the crack size, shape, pattern, and location.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

How to Identify, Diagnose, & Evaluate Masonry Block (concrete & "cinder block") Foundation & Wall Damage

History: We use the term concrete blocks in these articles where others may refer to this same construction material as concrete masonry unit (CMU), masonry blocks, cement blocks, or cinder blocks. Concrete blocks vary in quality, mostly as a function of the era in which they were made and the raw materials used. Henry Page Sr. in Poughkeepsie, NY in the early 1900's dug up the family farm, mixed dirt, cinders, and cement using a Sears & Roebuck cinder block kit to make masonry blocks that were used throughout Dutchess County. In time many of these blocks spalled and disintegrated badly where they were exposed to rain splash-up at ground level.

But rarely did these flimsy versions of the modern (and harder, stronger, concrete block) lead to a building failure from their innate properties. Rather most building failures involving concrete block are our own fault - causes which we inventory in these articles.

In masonry block construction, foundation or wall cracks occur more commonly in mortar joints but can also occur across and through the blocks themselves. Horizontal cracks in a concrete block wall are more immediately threatening of serious collapse than vertical cracks. Expansion and shrinkage cracks in a concrete block wall may occur but are less common than in some other materials. Cracks tend to be more severe in the center of walls from external loading and pressure (from any source). Cracks occurring near foundation corners in a masonry block wall are often from water and frost. In freezing climates, "frost lensing" can cause soil to stick to and lift a building foundation when the ground freezes. These cracks are usually visible above grade.

The masonry block foundation at the house in these photographs collapsed after a period of heavy rain. The underlying problem was in-slope grade at the rear of the home and trapped roof spillage there, causing lots of heavy wet earth pressure on the wall.

The home inspector had previously observed water damage at the wall and had correctly assessed the outside conditions. The owners had deferred action to prevent further water damage, leading to an unexpected and sudden precipitous collapse of the foundation after a period of unusually wet weather. [Left hand photograph courtesy of Alan Carson, Carson Dunlop, Toronto. These photos are of two different buildings.]

Some common masonry block (or "concrete block" or "cinder block") foundation or structural wall defects to be observed and reported include:

• Leaning or tipping masonry block walls: a concrete block or concrete masonry unit (CMU) wall may tip inwards at its top (a leaning or tipping wall failure) due to pressure from water and wet soils, from frost, from the weight of nearby vehicles driving along the wall (oil truck coming to deliver heating oil), or by defects and tipping wall footings.
• Buckled concrete block walls: often due to pressure or loading from water, frost, earth, or nearby passage of vehicles - potentially urgent depending on circumstances and amount. Bulging or buckling masonry block wall failures are also called "bending" failures.
• Horizontal displacement or "shear failures" occur in concrete block walls, particularly ones which were built without vertical steel reinforcement, and may be caused by pressure from water and wet soils or other forces. If we observe portions of a wall sliding horizontally past other wall segments we've found a shear failure.
  
  A common shear failure can be seen when the bottom course of masonry blocks in a foundation wall is held in place by a floor slab and when the upper portion of the wall has been pushed inwards so that the upper blocks are projecting past the lower ones.
  
  Such walls are also often tipping or leaning or may be buckled and broken open along horizontal mortar joints in the wall.
• Cracks in concrete block walls: along the mortar joints, or less often right through the masonry blocks themselves, can be the result of pressure from water and wet soils, frost, nearby vehicles, or differential settlement in a footing.

  If a foundation wall crack is vertical and fairly uniform in width, but the wall on one side of the crack is higher than on the other, we're looking at differential settlement which will probably be traced to the footings.

  If a foundation wall crack is vertical and wider at its top than its bottom, we may be looking at footing settlement in which the footings have "bent" and settled unevenly, such as when a footing has been placed over unevenly compacted fill or where there was bedrock or a large boulder under a portion of the footing permitting settlement such that the footing has settled down on one or both sides of this "high point".
  
  At least one author also posed that a concrete masonry unit wall which has a vertical crack near its center and whose crack is wider at its top than bottom has cracked due to wall shrinkage along its length. His explanation was that the top of the wall was free to shrink but its bottom was held in place by the footing, making a crack wider at top than bottom. However other experts (D.Wickersheim) assert that concrete block walls do not shrink significantly during curing, though wet masonry blocks might change a bit in dimension during drying.

• Crack patterns in concrete or other masonry foundation walls can occur as vertical, diagonal, stair-stepped, or horizontal patterns which we discuss and among which we distinguish in more detail at FOUNDATION CRACK EVALUATION

• Missing components such as headers where the wall has been modified, steel reinforcement wire or re-bar (if required by local codes).

• Missing footings, piers or other reinforcement
• Impact damage which has broken masonry blocks or dislocated them
• Point loading cracks or fractures
• Other cracks through or across concrete blocks as opposed to cracking in the mortar joints. Unlike poured concrete, concrete blocks do not shrink with age or curing. When investigating cracks through concrete blocks, check the other possibilities.
• Poured concrete sister walls, additions of pilasters, additions of steel reinforcement, or repeated re-coating of a wall with parging cement are all indications of past damage and/or water entry problems that merit further evaluation

FOUNDATION CRACK EVALUATION discusses detail the process of evaluating foundation cracks and signs of foundation damage by examining the crack size, shape, pattern, and location.
FOUNDATION BULGE or LEAN MEASUREMENTS explains a simple method for determining how much bulge or lean is present in a foundation or wall,
FOUNDATION MOVEMENT ACTIVE vs. STATIC helps determine if the foundation movement is ongoing,
FOUNDATION DAMAGE SEVERITY discusses how we decide the severity of foundation damage and the urgency of further action.
FAILURES by FOUNDATION TYPE & MATERIAL describes the types of foundation damage, cracks, leaks, or other defects associated with each type of foundation material (concrete, brick, stone, concrete block, etc.).

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

FOUNDATION CRACKS & DAMAGE GUIDE - how to inspect and diagnose foundation problems, in-depth diagnosis, and evaluation of all types of structural and non-structural cracks in residential foundations [Brick, Concrete, Masonry Block, Stone]
EARTHQUAKE DAMAGED FOUNDATIONS - examples of earthquake-damaged building foundations
FOUNDATION CONSTRUCTION TYPES - identify different foundation types, construction materials, effects of sequence of construction
FOUNDATION INSPECTION METHODS - what to look for when inspecting any building foundation
FAILURES by FOUNDATION TYPE & MATERIAL- unique failure characteristics of each foundation material
  Block Foundation & Wall Defects
  Brick Foundation & Wall Defects
  Brick Thermal Expansion Cracking
  Concrete Poured Foundation Wall & Slab Defects
  Concrete Pre-cast Foundation Defects
  Stone Foundation Defects
  Wood Foundation Defects
FAILURES by FOUNDATION MOVEMENT TYPE -recognize & diagnose types of foundation damage by the nature of foundation movement
  BULGED vs. LEANING FOUNDATIONS - distinction of foundation bulging from foundation leaning has important implications for stability
  COMBINATIONS OF FOUNDATION MOVEMENT - the real world of foundation cracks and movement: often more than one force is at work
    Bulge & step cracks
    Earthquake Damage to Foundations
    Flood Damage to Foundations
    Foundation Movement During Collapse
    Other Foundation Step cracks
  HORIZONTAL MOVEMENT IN FOUNDATIONS - detection, causes, effects, evaluation of horizontal or lateral foundation movement; hillsides
    Bulging, Leaning & Sliding Wall
    Horizontal Foundation Creep
    Horizontal Movement & step cracks in brick
    Impact Damage to Foundations
    Thermal Expansion Cracking in Brick
  VERTICAL MOVEMENT IN FOUNDATIONS - detection, causes, effects, evaluation of vertical foundation movement, differential settlement
    Diagonal Cracks in Concrete Foundations
    Diagonal Step Cracking in Masonry
    Differential vs. Uniform Settlement Cracks
    Leaning or Tipping Buildings
    Uniform Width vs. Tapered Foundation Cracks
    Vertical Cracks
FLOOD DAMAGE TO FOUNDATIONS - examples of flood damaged foundations, flood damage case analysis: were these cracks due to flooding?
FOUNDATION DEFECTS OF OMISSION - recognize things that were left out, like footings, reinforcement, soil compaction, during foundation construction
FOUNDATION CRACK EVALUATION- recognize & diagnose types of foundation cracks, movement, damage, by the size, shape, location, pattern of cracks
  DIAGONAL FOUNDATION CRACKS - causes and significance of diagonal foundation cracks, varies by foundation type & material
  HORIZONTAL FOUNDATION CRACKS - causes and significance of horizontal foundation cracks, varies by foundation type & material
  SHRINKAGE vs EXPANSION vs SETTLEMENT - which foundation materials shrink, which expand, & their characteristic crack patterns
  Sinkholes & Building Damage - sinkhole recognition, significance, cause, underlying geology, areas where sinkholes are worst
  VERTICAL FOUNDATION CRACKS - - causes and significance of vertical foundation cracks, varies by foundation type & material
FOUNDATION BULGE or LEAN MEASUREMENTS - procedure for documenting the amount of lean or bulge in a foundation or other building wall
FOUNDATION DAMAGE SEVERITY - rules of thumb for deciding how much foundation movement requires further action
FOUNDATION DAMAGE REPORTS - how to report foundation inspection results and damage
FOUNDATION INSPECTION STANDARDS - definition of scope of what a foundation inspector
FOUNDATION MOVEMENT ACTIVE vs. STATIC - determine if foundation movement was a one-time event or an ongoing problem
FOUNDATION REPAIR METHODS - catalog of methods used to repair damaged foundations and masonry building walls
  Bulged foundation Repairs
  Crack Repair Methods
  Horizontal Movement Repairs
  Shrinkage Crack Repairs
  Vertical Movement Repairs
SITE FACTORS AFFECTING FOUNDATIONS - drainage, rock, soil compaction, slope or grading, bedrock, sloping bedrock, proximity to roads
SLAB CRACK EVALUATION - recognize and diagnose different types of slab or concrete floor cracks and movement
  Control Joint Cracks in Concrete - what are control joints, why they are needed, what happens when they're omitted; are they structural?
  Freezing & Water Damage - recognize frost and water damage to concrete slabs, distinguish from other crack types
  Frost Heave/Expansive Soil Cracks in Slabs - distinguish between frost damage and expansive clay soil damage to slabs
  Seal Cracks by Polyurethane Foam Injection - stop basement or crawl space leakage
  Seal Cracks in Concrete, How To - products and methods used to seal or repair cracks in poured concrete walls, foundations, floors, & slabs.
  Settlement Cracks in Slabs - recognize slab settlement, assess risk, assess potential impact on structure
  Settlement Cracks vs. Frost Heaves - how to tell the difference between frost heaves and foundation settlement; does it matter?
  Settlement Cracks vs. Shrinkage Cracks - critical identification of shrinkage cracks (non-structural) compared with foundation movement
  Shrinkage Cracks in Slabs - causes, prevention, assessment of concrete slab shrinkage cracks
  Shrinkage Cracks Along Foundation Walls - why do we see a gap between a poured concrete slab and its abutting foundation wall?
  Standards for Repair of Cracks in Floors - when does a floor or slab crack need to be repaired? why?
WATER ENTRY in BUILDINGS
  SUMP PUMPS GUIDE - how a sump pump can avoid foundation damage and reduce building water entry
ADDITIONAL READING

• "Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
• "Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
• 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
• Aaron Kuertz aaronk@appliedtechnologies.com, with Applied Technologies regarding polyurethane foam sealant as other foundation crack repair product - 05/30/2007
• 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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