How to Evaluate the Significance of Foundation Movement or Damage
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How to Evaluate the Significance or Amount of Foundation Movement when a foundation is leaning, bulging, bowing, or settling.
This document describes how to recognize and diagnose various types of foundation failure or damage, such as
foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.
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.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Foundation DAMAGE SEVERITY - How to Evaluate the Significance or Amount of Foundation Movement when a foundation is leaning, bulging, bowing, or settling
The photo above shows a cracked, bulged, leaning stone foundation wall at the edge of an embankment - a condition we discuss further
at this website.
Historical data is a key observation or data that needs to be collected to assess the significance of any evidence of foundation movement
New or sudden foundation movement: If foundation cracking or movement is new, recent, or sudden: serious, prompt action is needed and you should consult an expert, in particular
if the amount is more than trivial. Trivial movement would be the discovery of a hairline crack (less than 1/16" in width) or a shrinkage crack
in a building foundation wall or floor slab. A word of caution: sometimes a crack has been present for a long time at a building but has simply
not been noticed by the building owner or occupants.
The first time such a crack is seen it may be mistaken for "new" and "sudden" when that's
not the case. See our discussion of SHRINKAGE vs EXPANSION vs SETTLEMENT for some examples.
Recurrent foundation cracking or movement: action is probably needed since recurrent movement can lead to cumulative damage to some structures
even if the amount of movement is not great. In particular, if you have made cosmetic repairs to a foundation or to plaster or drywall finished
areas above and supported by such a foundation you may see that the cracks you repaired have simply recurred.
Long term, continuing, but slow foundation movement: action may be needed, particularly if the effects of long term foundation
movement are cumulative.
Initial foundation cracking or other limited damage occurring at time of construction such as foundation
cracks in a masonry block wall which occurred during backfill may not need other than cosmetic repairs, in particular if there is no
evidence of subsequent foundation movement and still more likely if the initial damage and amount of movement was minor (say less than 1/2"
of inwards foundation wall bulge in the cracked areas.)
Foundation damage due to being struck: in this case the foundation will certainly need repair if the damage
to it was extensive with collapsed or severely dislocated components. Trivial foundation damage, say cracking a masonry block
on the corner of a garage with no basement below, is less likely to be significant.
Initial foundation settlement may not require additional repair. A hairline to 1/16" vertical crack in a concrete wall or
similar dimension step cracking in a masonry block wall may need cosmetic and sealant repair (to reduce leakage through the wall,
but if the initial amount of settlement was very small and is not ongoing, repair is unlikely to be needed.
These examples of foundation damage are almost always very important and need expert attention
Dislocated gas, plumbing, or electrical wiring or piping: NOTE: ANY foundation damage or crack associated with significant displacement of original structural or mechanical (gas/sewer lines) components is
likely to be significant. Even slight displacement is significant if mechanical systems may be unsafe (earthquake). Dislocated gas lines means
gas leaks are likely and there is serious damage of catastrophic explosion. Vacate the property, and immediately call the gas company from a telephone that is
not exposed to gas fumes.
Dislocated or broken structural connections such as a building which has shifted off of its foundation or has broken sill bolts or straps
connecting the foundation to the building framing needs expert investigation and repair.
Bulging foundation walls in response to area flooding are at risk of collapse; temporary support of the building and other measures
to relieve stress on the foundation may be needed. Do not delay in seeking expert advice in this situation.
Watch out: Bulging brick structural or veneer walls are very serious as the breakage of bond courses - which allows bulging - can indicate imminent and catastrophic structural collapse.
This list is not complete. Suggestions welcomed.
Some simple "rule of thumb" for evaluating the seriousness of foundation damage
Amount, type, & direction of foundation movement
Bulging brick - if broken bond courses, as we said above this is very serious/dangerous
(1/3 "rule" without breakage -A. Carson; author opinion: this needs clarification. 1/3 of wall thickness looks like much too much movement to allow--DF.)
Bulging masonry block - risk of collapse or sudden collapse, particularly if additional force such as water, melting snow, or vehicular traffic are applied
Diagonal cracks - usually indicate footing settlement or frost heave or frost lensing and in extreme cases may risk wall collapse.
Leaning foundation walls - may risk collapse if the amount of lean is significant (amounts are discussed in this and companion articles) or if movment has separated structural connections, with greater risk if additional force is applied just as cited above.
Vertical & horizontal dislocation in the foundation wall - depends on amount.
Horizontal cracks in a masonry unit (block or brick) present a higher risk of collapse than vertical cracks in the same walls, depending on the amount of disclocation.
Vertical cracks usually indicate footing settlement and may also need repair but usually present less risk of sudden catastrophic collapse unless the amount and nature of movement have separated structural connectors or supports such as posts or column footings.
The importance of the amount of foundation movement varies
These additional conditions change the importance of the amount of foundation movement
Wall type of construction
Wall construction materials
Implications for building: structure-pulled framing apart?
Site factors which increase risk: earth loading, such as from water, mud, snow, ice, frost, vehicle traffic
Climate, seismic, & other local foundation structural requirements
Earthquake design requirements for reinforcement
Cold-climate design requirements for reinforcement, drainage, frost protection
Storm/High-wind (and earthquake) design requirements for connections to framing (not considered here)
Other Expert Views regarding Evaluating Foundation Crack Size / Width or Extent of Foundation Movement
British Royal Institute of Chartered Surveyors, RICS - Degree of Damage - per W.H. Ransom (RICS)
Very slight/slight single, isolated cracks - Fine cracks, <5mm (.3") wide, slight sticking windows/doors
Moderate - 5-15mm (.2"-.6") wide, point up brick, some local replacement, doors/windows stick, pipes may break, not weather tight
Severe/very severe - > 15mm (.6") to > 25mm (1"), walls likely to lean, bulge, may require shoring; beams may lose bearing; windows distort, glass may break, pipes probably break. External repairs needed, partial or complete rebuild.
Multiple small cracks, leaning, shifting can be serious too.
Foundation DAMAGE SEVERITY TERMS - How to Characterize the Severity of Foundation Damage StructAPedia ®
Based on multiple national ASHI seminar polls conducted by the author - American Society of Home Inspectors (ASHI)
Minor, single, isolated, cosmetic, marketing concerns
Cracks, hairline to 1/16" horizontal
Cracks, hairline to 1/8" vertical and step; [1/4" ? per Alk - note that this is an unsubstantiated opinion]]
Cracks in slabs, hairline to 1/8", not extending into foundation
Modest foundation damage, monitoring appropriate
Horizontal bulge < 1.5", no signs of other significant damage
Leaning wall < 1/3 of wall thickness, from wall base (In author's opinion 1/3 is way too much movement to tolerate; a conventional thickness masonry block wall that leans in one inch over an 8' ht. (or maybe 1.5" per some surveys) might be monitored depending on other site conditions, history, etc. Walls buckled in or leaning more than 1" (or 1.5" in some jurisdictions) should be professionally evaluated further and may require near-term or even immediate repair; Walls buckled in or leaning an inch or less should be monitored.
If the cracks are old, with no sign of continuing/recurrent movement - the inspector is more likely to accept monitoring rather than requiring repair.
Cracks described by "wavy mortar" which were caused by damage during backfill while mortar was still "green" or soft (un-cured) and which are not accompanied by other signs of ongoing or additional movement, can be attributed to a single-event and may not require repair (depending on total amount of wall dislocation).
Significant, expert foundation assessment needed. Foundation repair may be needed
>1.5" horizontal bulge/lean or lateral dislocation >1/4".
Signs of active, recent, recurrent movement (may be seasonal or ongoing)
Sudden appearance of cracks, particularly in areas known to have sink-holes (e.g. some areas of the U.S. such as in Florida.) requires immediate assessment.
Signs of repeated repairs to foundation or interior
Cracks 1/4" [ 3/8" per Alk] & larger
Investigate any finding of which the inspector is uncertain or inexperienced.
WARNING: Don't make conclusions just based on crack size and location. The inspector must consider other site factors conditions,
history, materials, external forces, etc. Sudden catastrophes CAN occur, especially where site drainage or other conditions risk
undermining or sudden forces on the foundation.
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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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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.
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.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, 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. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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