How to Diagnose & Evaluate Horizontal Foundation Cracks InspectAPedia® -
How to Evaluate Horizontal Foundation Cracks
Pictures of types of foundation cracking & bulging
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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.
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.
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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Additional technical contributors & reference sources for this article are listed below.
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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, professor, school of structures division, UIUC - University of Illinois at Urbana-Champaign School of Architecture. Professor Wickersheimer specializes in structural failure investigation and repair for wood and masonry construction. * Mr. Wickersheimer's engineering consulting service can be contacted at HDC Wickersheimer Engineering Services. (3/2010)
*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.
2/3/99 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 our sections for my/our target of series of journal articles or a book.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328 This book is an update of a long-established text dating from at least 1988 (DJF); Quoting: This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations.THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.
Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting: A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
"Avoiding Foundation Failures," Robert Marshall, Journal of Light Construction, July, 1996 (Highly recommend this article-DF)
"A Foundation for Unstable Soils," Harris Hyman, P.E., Journal of Light Construction, May 1995
"Backfilling Basics," Buck Bartley, Journal of Light Construction, October 1994
"Inspecting Block Foundations," Donald V. Cohen, P.E., ASHI Reporter, December 1998. This article in turn cites the Fine Homebuilding article noted below.
"When Block Foundations go Bad," Fine Homebuilding, June/July 1998
Straw Bale Home Design, U.S. Department of Energy provides information on strawbale home construction - original source at http://www.energysavers.gov/your_home/designing_remodeling/index.cfm/mytopic=10350
More Straw Bale Building: A Complete Guide to Designing and Building with Straw (Mother Earth News Wiser Living Series), Chris Magwood, Peter Mack, New Society Publishers (February 1, 2005), ISBN-10: 0865715181 ISBN-13: 978-0865715189 - Quoting: Straw bale houses are easy to build, affordable, super energy efficient, environmentally friendly, attractive, and can be designed to match the builder’s personal space needs, esthetics and budget. Despite mushrooming interest in the technique, however, most straw bale books focus on “selling” the dream of straw bale building, but don’t adequately address the most critical issues faced by bale house builders. Moreover, since many developments in this field are recent, few books are completely up to date with the latest techniques. More Straw Bale Building is designed to fill this gap. A completely rewritten edition of the 20,000-copy best--selling original, it leads the potential builder through the entire process of building a bale structure, tackling all the practical issues: finding and choosing bales; developing sound building plans; roofing; electrical, plumbing, and heating systems; building code compliance; and special concerns for builders in northern climates.
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