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STRUCTURAL INSPECTIONS & DEFECTS

AGE of a BUILDING - how to determine

BASEMENT WATERPROOFING
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BUCKLED FOUNDATIONS due to INSULATION?
BUILDING SETTLEMENT

CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLD POUR JOINTS, CONCRETE
COLUMNS & POSTS, DEFECTS
CONCRETE FOUNDATIONS
CONCRETE FOUNDATIONS, PRE-CAST

DISASTER BUILDING INSPECTION & REPAIR

EARTHQUAKE DAMAGED FOUNDATIONS

FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOD DAMAGE TO FOUNDATIONS
FOOTING & FOUNDATION DRAINS
FOOTINGS EXPOSED, Repair Methods
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CONSTRUCTION TYPES
FOUNDATION CONTRACTORS, ENGINEERS
FOUNDATION CRACKS & DAMAGE GUIDE
FOUNDATION DEFECTS OF OMISSION - MISSING
FOUNDATION FAILURES by TYPE & MATERIAL
FOUNDATION FAILURES by MOVEMENT TYPE
FOUNDATION INSPECTION METHODS
FOUNDATION INSULATION OPTIONS
FOUNDATION MATERIALS, Age, Types
FOUNDATION REPAIR METHODS
FOUNDATION SETTLEMENT
FOUNDATION WATERPROOFING
FRAMING DAMAGE, INSPECTION, REPAIR
FRENCH DRAINS
FROST HEAVES, FOUNDATION, SLAB

GRADING, DRAINAGE & SITE WORK
GUTTERS & DOWNSPOUTS

INSECT INFESTATION / DAMAGE

MOBILE HOMES, DOUBLEWIDES, TRAILERS
MODULAR HOME CONSTRUCTION
MOISTURE CONTROL in BUILDINGS

RETAINING WALL DESIGNS, TYPES, DAMAGE
RETAINING WALL GUARD RAILINGS

SINKHOLES, WARNING SIGNS
SINKING BUILDINGS
SLAB CRACK EVALUATION
SLAB CRACK REPAIR
STONE FOUNDATIONS
STRAW BALE CONSTRUCTION
STRUCTURAL DAMAGE PROBING
STRUCTURAL WOOD ASSESSMENT

TERMITES
THERMAL EXPANSION of MATERIALS
TIMBER FRAMING, ROT
TIMBER ASSESSMENT

WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
WOOD FOUNDATIONS

More Information

Photograph of a cracked concrete slab from frost damage How to Repair Cracks or Settlement Damage in Poured Concrete Slabs & Floors
     

  • SLAB CRACK REPAIR - How to repair cracked concrete floors or slabs. Types of cracks that occur in concrete slabs, shrinkage cracks, settlement cracks, frost heaves; Causes and problems of floor slab cracking; Slab on grade construction or "patio home" construction cracks
  • SLAB CRACK EVALUATION - home
  • SLAB CRACK REPAIR - home
    • CRACK REPAIR STANDARDS for FLOORS - separate article
    • CONTROL JOINT CRACKS in CONCRETE - separate article
    • POLYURETHANE FOAM INJECTION - separate article
    • SEAL CRACKS in CONCRETE, How To - separate article
    • SHRINKAGE CRACK REPAIR - separate article
    • SLAB CRACK EVALUATION - separate article
    • VERTICAL FOUNDATION MOVEMENT REPAIR - separate article
  • FOUNDATION REPAIR METHODS - separate article
  • Questions & Answers about how to repair cracked or settled concrete slabs, floors, or foundations
  • References

Click to Show or Hide Related Topics

  • FOUNDATION DAMAGE & REPAIR GUIDE - home
  • BUILDING SETTLEMENT
  • DEFECTS LIST - STRUCTURE, FOUNDATION
  • DISASTER BUILDING INSPECTION & REPAIR
  • EARTHQUAKE DAMAGED FOUNDATIONS
  • FLOOD DAMAGED FOUNDATIONS
  • FOUNDATION CONSTRUCTION TYPES
  • FOUNDATION CONTRACTORS, ENGINEERS
  • FOUNDATION CRACK EVALUATION
  • FOUNDATION DAMAGE REPORTS
  • FOUNDATION DAMAGE SEVERITY
  • FOUNDATION DRAINS / FRENCH DRAINS
  • FOUNDATION FAILURES by MOVEMENT TYPE
  • FOUNDATION FAILURES by TYPE & MATERIAL
  • FOUNDATION INSPECTION METHODS
  • FOUNDATION INSPECTION STANDARDS
  • FOUNDATION INSULATION OPTIONS
  • FOUNDATION MATERIALS, Age, Types
  • FOUNDATION MISSING INCOMPLETE
  • FOUNDATION MOVEMENT ACTIVE vs. STATIC
  • FOUNDATION REPAIR METHODS
  • FOUNDATION WATERPROOFING
  • FRAMING DAMAGE, INSPECTION, REPAIR - home
  • FROST HEAVES, FOUNDATION, SLAB
  • SINKHOLES, WARNING SIGNS
  • SINKING BUILDINGS
  • SITE FACTORS AFFECTING FOUNDATIONS
  • SLAB CRACK EVALUATION
  • SLAB CRACK REPAIR
  • WATER ENTRY in BUILDINGS
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Concrete slab crack repair methods: this article describes methods for repair of cracks that occur in poured concrete slabs or floors and explains the need for accurate crack cause diagnosis and impact on structure before repairs are attempted. . Cracks in concrete floors or slabs occur in poured concrete slabs may be found both in basement and in slab on grade or "patio home" construction and have a variety of causes and cures that we discuss here. 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.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Repair Methods for Cracks in Concrete Slabs & Floors

Cracks in a concrete slab in an Alaska home over thawing permafrost (C) D FriedmanTypes 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.

Our photo (left) shows cracks developing in a slab on grade in a homein Alaska. Built over thawing permafrost, the cause of these cracks needs to be understood before a proper repair can be designed.

Readers should also see FOUNDATION REPAIR METHODS and see SINKING BUILDINGS where we include case histories of both building settlement and slab cracking, heaving, settling: diagnosis and repair. Also see How to Diagnose & Evaluate Foundation Cracks since those pages also assist in distinguishing among types of cracking in concrete foundations (vertical supporting walls and footings).

Accurate Diagnosis of Slab Crack Cause, Impact on Structure, Repair Needs

Before attempting to choose a repair method for concrete floor slab cracks,

Diagnose the cause of the slab movement and cracking. Only by an accurate diagnosis of the cause of cracking or movement in a floor slab can we be assured that the crack repair will be durable and appropriate. In fact some types of floor cracks, such as hairline concrete shrinkage cracks may not need repair at all.

In contrast, a concrete slab may have settled over poorly-compacted or washed-out fill (such as in some garages) without cracking (tipping instead), but repair may still be necessary to correct slope, provide drainage, or to prevent further settlement or even collapse.

Types of Cracks in Slabs

Each type of basement slab, floor slab, or slab on grade crack is discussed and described in articles at this website. Understanding the differences among these concrete crack types is an important first step in diagnosing their cause and their significance to the structure.

Photograph of a classic shrinkage crack in poured concrete.

  • Shrinkage cracks in a slab are unlikely to be of any structural concern but can be a source of water entry or radon entry in buildings and may form a tripping hazard. The photo at left shows a typical concrete slab shrinkage crack. Details are at Shrinkage Cracks in Slabs. Also see SHRINKAGE vs EXPANSION vs SETTLEMENT.

  • Settlement cracks in a slab indicate inadequate site preparation, such as failure to compact fill on which a slab was poured. See Settlement Cracks in Slabs for details.

  • Frost heaves or expansive soil damage can cause substantial damage to basement, crawl space, or garage floor slabs in some conditions. See Frost Heave/Expansive Soil Cracks in Slabs for details.

List of Slab Crack Repair Methods Articles

Crack at glass block in wall (C) D Friedman B ObrienPlease see the individual slab crack repair articles listed below

  • Control Joint Cracks in Concrete - adding control joints may be necessary to reduce further slab cracking if the joints were omitted in the original construction
  • Seal Cracks by Polyurethane Foam Injection - non-structural cracks (often the case with poured floor slabs) may simply need to be sealed in floors (or walls) to stop leaks
  • Seal Cracks in Concrete, How To - more poured concrete crack sealing methods
  • Standards for Repair of Cracks in Floors - so how bad does a crack have to be in order to decide that repair is necessary?

Cracks come to the job along with the concrete, riding in the same truck! At a Journal of Light Construction conference (Boston 1985) a lecturer informed us that "Every concrete truck that comes to your job to pour a slab has at least four cracks in it. It's up to you to either provide control joints, or not. If you leave out control joints the cracks will occur in a messier pattern at natural stress points in the slab."

The bad news about typical floating slab construction (where the soil is not compacted) is that anything that causes the soil to settle risks slab cracking and settlement. Flooding, leaks, or simply poor handling of roof and surface runoff can send water under a building where it causes loose soil to settle.

The good news about cracks in floating slab construction is that the damage is to the floor, not to the structure that is supporting the building. Only if you see a floor slab crack that continues up in the foundation wall where the crack meets the wall would the structure be obviously involved.

More good news: if there is significant soil settlement under a floating slab, the slab is likely to break and follow the settling soil downwards; a sudden precipitous collapse of a floating slab is less likely than the next case we describe.

Readers should also see FOUNDATION REPAIR METHODS and see SINKING BUILDINGS where we include case histories of both building settlement and slab cracking, heaving, settling: diagnosis and repair. Also see How to Diagnose & Evaluate Foundation Cracks since those pages also assist in distinguishing among types of cracking in concrete foundations (vertical supporting walls and footings).

Standards for Repair of Cracks in Concrete Floors

concrete crack patching with mortarSettlement cracks may form a tripping hazard even if they are not traced to a structural concern. While there are few construction acceptance standards for floor slab cracking, one, "Quality Standards for the Professional Remodeling Industry" NAHB, recommends that cracks in basement floors which exceed 3/16" in width or 1/8" in vertical displacement should be repaired.

The same standard provides that cracks in slab-on-grade floors shall not exceed 1/16" in width or in vertical displacement. The same standard provides that cracks occurring in control joints in concrete slabs are normal and acceptable. [We suggest that this last criteria should apply to crack width but not to vertical displacement.

See Standards for Repair of Cracks in Floors for details.


Frequently Asked Questions (FAQs) about how to repair cracks in poured concrete slabs or floors

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Questions & answers or comments about how to repair cracked or settled concrete slabs, floors, or foundations

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

  • Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
  • John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
  • Carson, Dunlop &
Associates Ltd., TorontoCarson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. 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:
    • Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
    • Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
    • Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
      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 Home Reference Book, a reference & inspection report product for building owners & inspectors.
      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.
    • The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
      Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
    • 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.
    • 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.
  • Quality Standards for the Professional Remodeling Industry, National Association of Home Builders Remodelers Council, NAHB Research Foundation, 1987.
  • Quality Standards for the Professional Remodeler, N.U. Ahmed, # Home Builder Pr (February 1991), ISBN-10: 0867183594, ISBN-13: 978-0867183597
  • "Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
  • 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
  • Thanks to reader Michael Witten for technical editing, October 2010
  • 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
  • Aaron Kuertz aaronk@appliedtechnologies.com, with Applied Technologies regarding polyurethane foam sealant as other foundation crack repair product - 05/30/2007
  • 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

 

How to Identify & Evaluate Shrinkage Cracks in Poured Concrete Slabs

Please see the main text version of this article at Shrinkage Cracks in Slabs

We discuss the recognition and significance of concrete shrinkage cracks in detail at Shrinkage Cracks in Slabs. Just below you can read a summary of this topic.

Photograph of a classic shrinkage crack in poured concrete.

Shrinkage cracks in poured concrete are easily recognizable and can be distinguished from other types of cracks that occur later in the life of a foundation wall or floor slab.

The photograph of cracks above were taken of shrinkage cracks in a concrete slab floor in a home built in 2006. The cracks in this case ranged in width (measured across the crack) from "hairline" (less than 1/16") to about 3/32" in the basement floor slab of this particular home. They may appear larger.

What is unique about shrinkage cracks in concrete is that they usually appear to be discontinuous, as shown in this photo. The crack will meander along in the concrete, taper to a stop, and then continue beginning in a parallel line to the first crack, meandering again through the concrete. This is characteristic of concrete (or mud) shrinking while giving up its moisture.

You can see the shrinkage of even a perfect concrete floor slab with no visible cracks in the field of its surface if the floor was poured inside of an existing foundation. Look for the gap between the edges of the slab and the foundation wall? Look also for the stains or concrete debris on the wall at the slab level? These confirm that at the time the slab was poured it was touching the wall.

Shrinkage Cracks in a Basement or other Slab May Be Severe and May Combine with Settlement

Concrete shrinkage crack Concrete shrinkage and settlement

Depending on the mix and pour conditions as well as the site work preparation significant concrete shrinkage cracks can appear in a basement slab. On occasion we may also see vertical dislocation in a floor slab crack, that is, one side has settled or tipped away from the other side of the cracked concrete.

Our photographs above show shrinkage cracking and ensuing minor settlement cracks occurring in the same poured concrete basement floor. We suspected that site drainage defects or possibly nearby site blasting for additional construction contributed to the 1/16" to 1/8" vertical dislocation across some of the cracks in this floor where the cracks were about 3/16" wide.

Slab Cracks may Permit Basement Water Entry or Radon Gas Entry

Happily the building owner at the site where we made the photos above did not report water entry through these openings, though it certainly might be expected as the home ages and its footing drains stop working, particularly if surface runoff and roof runoff are not kept away from the building.

Photos of Concrete Floor Slab Shrinkage Points of Origin

Concrete shrinkage start points at corners

The photo at left shows some concrete shrinkage cracks that are larger than usual. Note that these cracks begin at building foundation wall inside projection corners - a condition that probably creates stress points as the slab cures.

If you click on and enlarge the photo you can see clear evidence that the cracks are discontinuous, multiple, and very roughly parallel in this area - good evidence that they were caused during the concrete curing process and not by a later event which "broke" the slab.

When we see combined slab shrinkage and slab settlement condition we suspect that the concrete pour not only allowed for excessive shrinkage, or perhaps shrinkage without control joints, but also the pour was made on top of poorly prepared soils. For example if a slab is poured on poorly-compacted soil, after shrinkage cracking occurs, we may see uneven settlement among sections of the cracked slab.

Settlement cracking following shrinkage cracking may also occur. In both of these cases we anticipate that significant horizontal dislocation in a poured concrete slab should be small unless steel reinforcement was omitted or was improperly installed. Since some contractors use a fiber-reinforced cement and may omit steel reinforcement in floor slabs, this condition may occur.

How to Inspect & Evaluate Cracks at Control Joints in Concrete

We discuss the recognition and significance of control joints in poured concrete slabs in detail at Cracks at Control Joints in Concrete. Just below you can read a summary of this topic.

Photograph of a concrete slab control joint Photograph of a cracked concrete slab, cracks at a control joint

The first photograph shows an expansion joint in a basement floor slab. Notice that we do not see other cracks in this slab. Shrinkage cracks that occur at control joints such as shown in the second, close up photo here, are occurring where they are supposed-to, although the width of this particular crack was surprisingly large. These cracks are not normally a defect in the slab but may be a source of water or radon entry into the building and may need to be sealed. Use a flexible sealant.

Settlement Cracks in poured Concrete Slabs

We discuss the recognition and significance of settlement cracks in poured concrete slabs in detail at Settlement Cracks in Slabs. Just below you can read a summary of this topic.

Photograph of a cracked concrete slab, cracks around a Lally column

Settlement cracks in a conventional concrete floor slab which has been poured inside a separate foundation wall (and often resting at its edges on the building's foundation wall footings) are usually not connected to the foundation wall and are not supporting any structure [except possibly Lally columns, discussed next].

These cracks may not be a structural concern, but there are cases where a serious hazard can be present, such as garage floor cracking when the floor was poured over soft, loose, inadequately-compacted fill and where the floor slab was not pinned to the garage foundation walls. Soil settlement under a garage floor, perhaps aggravated by groundwater which can increase soil settlement, can lead to first hollowing-out of space below the floor and second, sudden collapse of the floor structure.

We have used a heavy chain, dragging it across the garage floor and listening to changes in the sound it produces, to find areas of significant soil voids below the floor. The pitch of the chain noise drops significantly when passing over a void below the concrete.]

Settlement cracks in a concrete floor around a supporting Lally column might be indicative of a serious problem such as building settlement if the columns are settling. Independent footings may have been provided supporting Lally columns in the building interior and those may be settling independently of the floor slab which may have been poured around and even over them (See photo above). But beware, where slab thickness and local building codes allow, supporting columns may bear directly on a poured floor slab without their own (deeper) pier or footing. In that case floor slab cracking and settling can cause column movement and may be a structural concern.

Settlement cracks in a monolithic slab or floating slab floor may be more serious, depending on their extent since in this case the edges and other portions of the slab are, unlike the cases above) expected to support the upper portions of the building structure.

A monolithic concrete slab is one which includes the building footing as part of the slab, created in a single continuous pour of concrete.

A floating concrete slab is one which is poured at a (generally) uniform thickness on the ground without a separate footing. [Beware, in areas of wet soils, expansive clays, freezing climates, or unstable soils, floating slabs may be exposed to extra stresses and may tip or crack. Proper site work and drainage are important as is proper engineering design of such structures.

Frost Heaves or Expansive Soil Cracks in Poured Concrete Slabs

We discuss the recognition and significance of frost heaving damage and cracks in poured concrete slabs in detail at Frost Heave/Expansive Soil Cracks in Slabs. Just below you can read a summary of this topic.

Photograph of a cracked concrete slab from frost damage

Frost heaves or expansive soils damage to building floor slabs can range from minor to extensive in buildings depending on soil and weather conditions, site preparation, and slab construction details, as we elaborate here.

The photograph above shows a rather straight crack across a garage slab near the garage entry door. What is happening here and why is this particular crack straight if it's a frost or soil heave crack?

In freezing climates building foundations include a footing which extends below the frost line. This is true for both the occupied space as well as garages. When a concrete slab is poured either abutting the top of such a foundation, or poured extending over the edges of such a foundation, there is risk of cracking across the concrete at the interior edge of the buried footing.

The combination of water under a garage floor (watch out for driveways and sites that slope towards the garage or home) and freezing can cause the portion of the slab which rests directly on the soil to move up and down during freeze/thaw cycles. Since a garage is often colder near the garage entry door than in other areas, there is extra risk of these cracks occurring there, but they can occur anywhere. When there is freezing and heaving of a slab, particularly one which omitted reinforcing steel, or did not extend the steel over the footing, these garage floor slab cracks may appear during freeze/thaw cycles.

Similar floor slab damage might occur in areas of expansive clay soils if the proper moisture level is not maintained.

Basement floor heave patterns - frozen floor drains: Basement floors can be frost heaved in other patterns in buildings which are unheated or which lose heat. We have found basement floor slabs broken and heaved above buried drain lines which ran below the basement floor of a home which remained unheated during freezing weather.

A clogged drain sitting full of liquid combined with prolonged freezing weather was the culprit in most of these cases. The heaved concrete was raised following exactly the path of the frozen (and burst) buried, clogged drain line. This problem can be epidemic in older homes which were constructed using a downspout drain line extending below the basement slab.

Photograph of a cracked concrete slab from frost damage

 

Basement and garage floor random heave and crack patterns: Cracked and heaved concrete or settled concrete can occur in more random patterns in any concrete floor where there has been frost heaving, soil contraction/expansion, or simple soil settlement, as shown in this photograph.

Garage or basement floor sloped or semi-uniform settlement may also produce a tipped floor even if the concrete is not cracked, or the floor may settle uniformly. This condition occurs if the concrete was reinforced by steel or fiber cement, but was poured inside of a separate concrete or masonry block foundation. We see this condition more often in garages in which the slab was reinforced but poured on poorly-compacted soil. The problem may be worst if in addition to poor compaction, water runs under the slab, causing additional or more rapid soil settlement.

My first construction job (for pay) was to rake level the backfill soil that the contractor had dumped inside of the newly-completed garage foundation in a series of homes. No compaction of any kind was performed. When a lot of fill, several feet or more in depth, was required to bring the slab to the desired height, there was a good chance that the slab would settle or tip in the future.

Garage slabs which were poured inside of the foundation walls but which were pinned to the foundation sides (typically using re-bar set into holes punched into the masonry block foundation), the slab was resistant to settlement or movement even if there was modest soil settlement below.

In a garage where the slab has settled you can often spot the original level of the slab and thus can measure the amount of settlement. Look for a concrete line above the level of the top of the slab and found along the masonry block or poured concrete foundation wall. we have seen this line ranging from a fraction of an inch to six to eight inches above the current level of the slab!

Standards for the Acceptance or Repair of Cracks in Concrete Floors in New Construction

Settlement cracks may form a tripping hazard even if they are not traced to a structural concern. While there are few construction acceptance standards for floor slab cracking, one, "Quality Standards for the Professional Remodeling Industry" NAHB, , recommends that cracks in basement floors which exceed 3/16" in width or 1/8" in vertical displacement should be repaired. The same standard provides that cracks in slab-on-grade floors shall not exceed 1/16" in width or in vertical displacement. The same standard provides that cracks occurring in control joints in concrete slabs are normal and acceptable. [We suggest that this last criteria should apply to crack width but not to vertical displacement.]

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.
  • Home Reference Book - Carson DunlopThe 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.

    Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
  • Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
  • Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
  • The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for certain articles found at this website. All rights and contents to those materials are ©Journal of Light Construction and may not be reproduced in any form.
  • Appliances and Home Electronics, - energy savings, U.S. Department of Energy
  • Avongard foundation crack progress chart for structural crack monitoring
  • Basement Moisture Control, U.S. Department of Energy
  • Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
  • Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
  • The Circular Staircase, Mary Roberts Rinehart
  • Construction Drawings and Details, Rosemary Kilmer
  • Crawl Space Moisture Control, U.S. Department of Energy
  • 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.
  • Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3
  • Domestic Building Surveys, Andrew R. Williams, Kindle book, Amazon.com
  • 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.
  • Guide to Domestic Building Surveys, Jack Bower, Butterworth Architecture, London, 1988, ISBN 0-408-50000 X
  • "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
  • Slab on Grade Foundation Moisture and Air Leakage, U.S. Department of Energy

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