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This article explains how to identify types of foundation construction, methods, materials as an aid to diagnosing foundation damage. Understanding what foundation materials were used, how a foundation was constructed, and the sequence of construction steps are key elements in accurate diagnosis of foundation cracks, bowing, collapse or other problems as well as in planning for foundation repair.
This article series 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.
Foundation Construction Materials & Methods: How to Identify Foundation Construction Type, Materials, Sequence
The photo above shows a concrete block foundation wall which had been damaged by water and frost, exacerbated by construction very close to bedrock which sloped to the foundation wall from the surface, trapping roof runoff against the building.
A thick concrete laminate wall has been added inside to stabilize the wall (but no proper steps had been taken outdoors to redirect water away.)
At this website
we explain how it is sometimes possible to be confident about the cause of foundation damage which in turn helps assess
the risk presented to the building.
Photographs of types of foundation cracks and other foundation damage: we have a large library of photographs which
continually add to this website. Pending completion of that work, contact the author if assistance is required.
Foundation Construction Types
The type of foundation construction affects how a foundation may be damaged, cracked, settled, or moved.
Slab-on-grade - (Sketch at left courtesy Carson Dunlop Associates) Definition of slab on grade foundation: concrete is placed directly onto a prepared soil surface. Modern slab on grade construction usually provides for solid foam insulation below the slab and may use steel reinforcement (re-bar) or fiber-reinforced concrete to resist cracking.=
Control joints are important to avoid other foundation cracks. Slab on grade foundations and floors are vulnerable to shrinkage cracks (often not significant), settlement on poorly-prepared sites.
Photos of slab on grade foundations and floor slabs are included in the following article series:
Monolithic slabs - (shown at left slab on grade construction, sketch courtesy of Carson Dunlop Associates.) Definition of monolithic slab foundation: poured concrete footings and the concrete floor are poured simultaneously as one continuous system.
Excavation and concrete forms are used to form the footing and foundation wall portions of the structure. Monolithic slab foundations are resistant to problems over sink holes / clay
Supported slabs - (see slab on grade illustration above)
Definition of a supported slab foundation: a poured concrete slab is supported on footing/foundation/pins. Vulnerable to hairline step cracks in block walls that rest on the slab; (FL per Mark Cramer). Cracks that are hairline to 3/16 common at the top of slab elevation (in FL-Cramer)
Floating slabs - (shown at left floating slab construction, sketch courtesy of Carson Dunlop Associates.) Definition of a floating slab: a flat concrete slab, typically reinforced with steel re-bar or steel wire mesh is poured on (hopefully) prepared soil and is not supported by a surrounding foundation.
Floating slabs may be used inside of concrete, block or other foundation walls, for example in garages.
Some poured slabs are pinned to a surrounding foundation wall to prevent tipping or settlement - and thus are no longer technically free-floating.
In sum the slab is not connected to a separate building foundation wall. The slab is reinforced and "floats" on supporting soil.
Crawl spaces, foundations - wall height is a key factor in predicting crawl space failures. Special crawl space wall and knee-wall reinforcement is required in earthquake areas. Also see CRAWL SPACES.
Basement - wall height vs block width/reinforcement: taller basement walls may require additional reinforcement to resist buckling and bulging. See FOUNDATION BULGE or LEAN MEASUREMENTS.
Building Additions, foundations - connection to original, varying materials, varying footing depths. Watch for differential settlement cracks and foundation leaks where old and addition foundations meet.
Actual footing/foundation type is usually not visible, that is, the poured footing, or gravel, or other details that are below ground may be inferred, known from photographs taken during construction, supposed from building plans and drawings, but the actual details are buried unless excavation is performed to permit an inspection.
The type of foundation materials (listed below) affects how a foundation may be damaged, cracked, settled, or moved and significantly, the foundation material must be considered in understanding pattern, location, size, and significance of cracks or other signs of foundation movement. The same crack location size may have different significance in different foundation materials.
Masonry block for building foundations
Poured concrete for building foundations
Brick for building foundations
Stone for building foundations
Wood for building foundations
Pre-cast Concrete for building foundations
Our photo at left shows a poured concrete foundation wall.
can lead to sudden precipitous and catastrophic building collapse, dangerous conditions may be present at some properties.
Foundation Construction Sequence Considerations
Our photo at left shows a reconstructed concrete block foundation after a collapse.
The original construction included in-slope grade at the rear of this building, combined with poorly-drained soils and runoff which was trapped against the building.
The concrete block foundation collapse at this building occurred more than twenty years after construction and might have been avoided by proper handling of roof runoff, the immediate failure cause, but the site shape and failure to provide proper surface and subsurface drainage were important factors in this foundation failure too.
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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.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones