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How to Diagnose & Evaluate Diagonal Foundation Cracks StructAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com How to Evaluate Diagonal Foundation Cracks Photographs of types of foundation cracks

This chapter of the "Foundation Crack Bible" discusses in detail the process of evaluating foundation diagonal foundation cracks, step cracks, and signs of foundation damage. 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. Also see FOUNDATION BULGE or LEAN MEASUREMENTS which explains a simple method for determining how much bulge or lean is present in a foundation or wall, then see FOUNDATION MOVEMENT ACTIVE vs. STATIC which helps determine if the foundation movement is ongoing, and see FOUNDATION DAMAGE SEVERITY for a discussion © 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.

DIAGONAL FOUNDATION CRACKS - Diagonal & Step Crack Patterns in Building Foundations

This settlement crack probably occurred during initial footing settlement. Notice that it is wider at the top than the bottom of the crack. This suggests that the footing to the left or right of the crack has moved downwards, with further downwards movement as we move further from the crack itself. If this is new construction and the crack does not change in width the site conditions may have stabilized.

Clues to help diagnose the probable cause of diagonal foundation cracks in buildings:

• From corner towards adjacent opening, wider at top than bottom - often due to foundation settlement, expansive clay soil, frost damage, or damage from a shrub/tree close to the foundation wall.
• Under a ground floor window, from sill to ground, sill bowed up - often due to foundation heave, clay soil, frost, shallow or absent footings
• In the foundation wall anywhere, wider at bottom than top - settlement under building
• At building corners in cold climates - frost heave, frost lensing, shallow footings, water problem, or insufficient backfill. In a typical raised ranch with a garage located in part of the basement, and with the garage entering at one end of a home, we often find step cracks in the front and rear foundation walls only on the garage-end of the home. These cracks may correspond to some related observations: (1) there may be less backfill against the front and rear foundation walls where a garage entry is located between them; (2) the reduction in backfill combined with an un-heated garage may expose these building corners to more frost damage; (3) if a building downspout or gutter defect spills roof drainage against the building wall, these forces will often combine to make more severe frost cracks appear on the garage-entry end of the home.
• Vertical or diagonal crack which over a short time - settlement over sink holes- serious, open suddenly after rain; or ravines, mulch, fill, organic debris (later rots and settles).
• Over window/door, straight or diagonal - loading/header defect - may appear as horizontal along top or bottom of header, vertical at ends of header (possibly due to differences in thermal expansion of different materials of header vs. wall) or vertical/diagonal at center of header (loading failure) or at corners (possible point-load failure)
• 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, usually in fact a discontinuous crack in the hairline area, are usually shrinkage cracks and should not be ongoing nor of structural significance, though they may invite water entry through the wall.

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

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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.
• 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
• 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

Technical Edits, Changes, Amendments to This Document

• 06/07/2007 adding text, illustrations, content
• 9/23/2006 editing to clarify text and add content; Technical review (partial) by Arlene Puentes.
• 4/17/2006 editing to clarify text in several sections.
• 2/6/99 editing updates, soliciting additional reviews
• 2/3/99 Converted working text file to MSWord97 .doc and .htm files for easier review on Internet
• 6/26/95 text updates per comments from Al Carson, Terry Carson, Mark Cramer 6/16/95 text updates for Calgary July 1995
• cc's sent to reviewers
• 3/28/95 uploaded to ASHI's Internet site - asfoun01.txt
• 11/19/93 Ed Seaquist - telecon 11/19/93, likes, will write up one of my sections for my/our target of series of journal articles or a book.
• © Dan Friedman 1999, original 1992 All Rights Reserved -- foundation.htm

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