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How to Diagnose & Evaluate Horizontal Foundation Cracks StructAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com How to Evaluate Horizontal Foundation Cracks Pictures of types of foundation cracking & bulging

This chapter of the "Foundation Crack Bible" discusses in detail the process of recognizing & evaluating horizontal foundation 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 of just how much foundation movement is likely to be a concern. Readers should also see How to Evaluate Cracks in Poured Concrete Slabs & Floors since those pages also assist in distinguishing among types of cracking in concrete. 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. © 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.

HORIZONTAL FOUNDATION CRACKS - Patterns

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.

• Cold climates- frost, possible displacement inwards
• Possible vehicle loading, displacement inwards

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.

• Possible vehicle loading (look for a driveway near the wall or site history involving movement of heavy equipment near the wall)
• Backfill damage - excessive height or premature backfill before the first floor framing was in place.
• Hillsides - earth loading or earth loading exacerbated by water or frost
• Areas of wet soils - likely to be earth-loading or earth loading exacerbated by water or frost

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.

• Earth Loading, especially if in an area of dense or wet soils
• Horizontal dislocation of a masonry block or brick wall may appear first as a crack and then later as horizontal movement as a wall is pushed inwards by earth or wet soil pressure.

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:

• Shallow garage footings: The garage foundation footings are less deep than the house footings, exposing the foundation to other risks of frost or settlement damage and movement.
• Garage additions: The garage may have been added after original construction, creating newly-disturbed soils around the foundation and footings that have settled more recently than that of the original home.
• Garage slab settlement and cracking: A garage foundation is often constructed as a concrete footing and a low masonry block wall, followed by dumping fill inside this structure to raise the level of the garage slab to the desired height. A common construction error is the omission of adequate soil compacting before the garage slab is poured. A related common construction shortcut for these "raised slabs" (on fill, higher than and not resting on the garage wall foundation footings), is the omission of pins connecting the slab to the garage foundation wall at its elevated position. The result of these details is that as the soils below the slab settle and compact the slab can move and settle significantly. Depending on the amount of garage floor slab reinforcement (wire or re-bar or none), the slab may crack as well as tip and settle. How does garage slab settlement crack the garage foundation walls? The weight of a garage floor slab, combined with the weight of vehicles in the garage, compresses the soil below the slab. Soil pressure includes an outwards force which can cause horizontal cracks in a masonry block garage foundation wall. Look for these cracks outside the garage and above grade-level.
• Detecting soil voids below a garage slab is quite possible using this "ghost busters" technique: drag a heavy chain across the floor and listen to the sound it produces. If the chain moves across an area of soil void you'll hear a change in pitch in its sound, typically dropping lower. This is not a technique for every building inspection but it is useful when evaluating garage floor slab movement, tipping, cracking, or 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.

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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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