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How to Inspect & Diagnose Concrete Block Foundation Cracks, Leans, Bows, Settlement StructAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com

• 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 "cinderblock" 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 2008 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

In masonry block construction, foundation or wall cracks occur more commonly in mortar joints but can also occur across blocks. Horizontal cracks are more immediately threatening of serious collapse than vertical cracks. Expansion and shrinkage cracks 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 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 preciptious 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 defecdts 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 thge 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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FOUNDATION DIAGNOSIS Chapter Index

To continue reading this building foundation inspection, diagnosis, and repair guide, use links to the document chapters at left or below. Links shown in green font indicate where you are in this document.

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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.
• "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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