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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FOUNDATION INSPECTION METHODS FAILURES by FOUNDATION TYPE & MATERIAL Block Foundation & Wall Defects Brick Foundation & Wall Defects Brick Thermal Expansion Cracking Concrete Poured Foundation Wall & Slab Defects Concrete Pre-cast Foundation Defects Stone Foundation Defects Wood Foundation Defects FAILURES by FOUNDATION MOVEMENT TYPE BULGED vs. LEANING FOUNDATIONS COMBINATIONS OF FOUNDATION MOVEMENT Bulge & step cracks Earthquake Damage to Foundations Flood Damage to Foundations Foundation Movement During Collapse Other Foundation Step cracks HORIZONTAL MOVEMENT IN FOUNDATIONS Bulging, Leaning & Sliding Wall Horizontal Foundation Creep Horizontal Movement & step cracks in brick Impact Damage to Foundations Thermal Expansion Cracking in Brick VERTICAL MOVEMENT IN FOUNDATIONS Diagonal Cracks in Concrete Foundations Diagonal Step Cracking in Masonry Differential vs. Uniform Settlement Cracks Leaning or Tipping Buildings Uniform Width vs. Tapered Foundation Cracks Vertical Cracks FLOOD DAMAGE TO FOUNDATIONS FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION DIAGONAL FOUNDATION CRACKS HORIZONTAL FOUNDATION CRACKS SHRINKAGE vs EXPANSION vs SETTLEMENT Sinkholes & Building Damage VERTICAL FOUNDATION CRACKS FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION INSPECTION STANDARDS FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION REPAIR METHODS Bulged foundation Repairs Crack Repair Methods Horizontal Movement Repairs Shrinkage Crack Repairs Vertical Movement Repairs SITE FACTORS AFFECTING FOUNDATIONS SLAB CRACK EVALUATION Control Joint Cracks in Concrete Freezing & Water Damage Frost Heave/Expansive Soil Cracks in Slabs Seal Cracks by Polyurethane Foam Injection Seal Cracks in Concrete, How To Settlement Cracks in Slabs Settlement Cracks vs. Frost Heaves Settlement Cracks vs. Shrinkage Cracks Shrinkage Cracks in Slabs Shrinkage Cracks Along Foundation Walls Standards for Repair of Cracks in Floors WATER ENTRY in BUILDINGS SUMP PUMPS GUIDE ADDITIONAL READING More Information InspectAPedia TM Home & Site Map Air Conditioning InspectAPedia Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Bias Pledge Contact Us |
This article describes the types of cracks that occur in poured concrete slabs or floors and explains the risks associated with each, thus assisting in deciding what types of repair may be needed. This website 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. Readers should 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). © 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. Three Types of Cracks in Concrete Slabs & Floors
Each type of basement slab, floor slab, or slab on grade crack is discussed and described with photographs below. 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."
Three Types of Poured Concrete Slab Floors - Different Implications of Cracks & MovementBefore we describe crack, movement, and damage patterns and diagnosis in concrete slabs, we need to introduce three different types of poured concrete floor slabs. We use the three Carson Dunlop Sketches shown here to comment on the occurrence, causes, and significance of cracks and movement in poured concrete slab construction. 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. Supported poured concrete floor slab characteristics
Slab on Grade - Monolithic Concrete Slab Construction Characteristics
The articles listed below explain how we recognize and diagnose signs of cracking, damage, movement in these different concrete slab construction methods. Use links just below or 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. SLAB CRACK EVALUATION
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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION INSPECTION METHODS SITE FACTORS AFFECTING FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FAILURES by FOUNDATION TYPE & MATERIAL FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION VERTICAL FOUNDATION CRACKS DIAGONAL FOUNDATION CRACKS HORIZONTAL FOUNDATION CRACKS SHRINKAGE vs EXPANSION vs SETTLEMENT Sinkholes & Building Damage SLAB CRACK EVALUATION Shrinkage Cracks in Slabs Cracks at Control Joints in Concrete Settlement Cracks in Slabs Freezing & Water Damage Frost Heave/Expansive Soil Cracks in Slabs Settlement Cracks vs. Frost Heaves Settlement Cracks vs. Shrinkage Cracks How to Seal Cracks in Concrete Polyurethane Foam Injection Standards for Repair of Cracks in Floors FAILURES by FOUNDATION MOVEMENT TYPE FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION REPAIR METHODS ADDITIONAL READING FOUNDATION INSPECTION STANDARDS More Information InspectAPedia TM Home & Site Map Structure Accuracy & Bias Pledge Contact Us |
Shrinkage Cracks in Poured Concrete SlabsWe 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. 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. | |||
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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION INSPECTION METHODS SITE FACTORS AFFECTING FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FAILURES by FOUNDATION TYPE & MATERIAL FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION VERTICAL FOUNDATION CRACKS DIAGONAL FOUNDATION CRACKS HORIZONTAL FOUNDATION CRACKS SHRINKAGE vs EXPANSION vs SETTLEMENT Sinkholes & Building Damage SLAB CRACK EVALUATION FAILURES by FOUNDATION MOVEMENT TYPE FOUNDATION BULGE or LEAN MEASUREMENTS Shrinkage Cracks in Slabs Shrinkage Cracks Along Foundation Walls Cracks at Control Joints in Concrete Settlement Cracks in Slabs Freezing & Water Damage Frost Heave/Expansive Soil Cracks in Slabs Settlement Cracks vs. Frost Heaves Settlement Cracks vs. Shrinkage Cracks How to Seal Cracks in Concrete Polyurethane Foam Injection Standards for Repair of Cracks in Floors FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION REPAIR METHODS ADDITIONAL READING FOUNDATION INSPECTION STANDARDS More Information InspectAPedia TM Home & Site Map Structure Accuracy & Bias Pledge Contact Us |
Cracks at Control Joints in ConcreteWe 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.
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. 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. | |||
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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION INSPECTION METHODS SITE FACTORS AFFECTING FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FAILURES by FOUNDATION TYPE & MATERIAL FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION VERTICAL FOUNDATION CRACKS DIAGONAL FOUNDATION CRACKS HORIZONTAL FOUNDATION CRACKS SHRINKAGE vs EXPANSION vs SETTLEMENT Sinkholes & Building Damage SLAB CRACK EVALUATION Shrinkage Cracks in Slabs Shrinkage Cracks Along Foundation Walls Cracks at Control Joints in Concrete Settlement Cracks in Slabs Freezing & Water Damage Frost Heave/Expansive Soil Cracks in Slabs Settlement Cracks vs. Frost Heaves Settlement Cracks vs. Shrinkage Cracks How to Seal Cracks in Concrete Polyurethane Foam Injection Standards for Repair of Cracks in Floors FAILURES by FOUNDATION MOVEMENT TYPE FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION REPAIR METHODS ADDITIONAL READING FOUNDATION INSPECTION STANDARDS More Information InspectAPedia TM Home & Site Map Structure Accuracy & Bias Pledge Contact Us |
Settlement Cracks in poured Concrete SlabsWe 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. 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. 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. | |||
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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION INSPECTION METHODS SITE FACTORS AFFECTING FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FAILURES by FOUNDATION TYPE & MATERIAL FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION VERTICAL FOUNDATION CRACKS DIAGONAL FOUNDATION CRACKS HORIZONTAL FOUNDATION CRACKS SHRINKAGE vs EXPANSION vs SETTLEMENT Sinkholes & Building Damage SLAB CRACK EVALUATION Shrinkage Cracks in Slabs Shrinkage Cracks Along Foundation Walls Cracks at Control Joints in Concrete Settlement Cracks in Slabs Frost Heave/Expansive Soil Cracks in Slabs Settlement Cracks vs. Frost Heaves Settlement Cracks vs. Shrinkage Cracks How to Seal Cracks in Concrete Polyurethane Foam Injection Standards for Repair of Cracks in Floors FAILURES by FOUNDATION MOVEMENT TYPE FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION REPAIR METHODS ADDITIONAL READING FOUNDATION INSPECTION STANDARDS More Information InspectAPedia TM Home & Site Map Structure Accuracy & Bias Pledge Contact Us |
Frost Heaves or Expansive Soil Cracks in Poured Concrete SlabsWe 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. 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. 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. I've seen this line ranging from a fraction of an inch to six to eight inches above the current level of the slab! 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. | |||
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FOUNDATION DIAGNOSIS |
Standards for the Acceptance or Repair of Cracks in Concrete Floors in New ConstructionSettlement 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.] FOUNDATION DIAGNOSIS Chapter IndexUse links just below or 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. FOUNDATION DIAGNOSIS - how to inspect and diagnose foundation problems, in-depth diagnosis, and evaluation of all types of structural and non-structural cracks in residential foundations [Brick, Concrete, Masonry Block, Stone] Technical Content Reviewers for Foundation Crack and Movement Damage Evaluation, Diagnosis, & Reporting
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FOUNDATION DIAGNOSIS EARTHQUAKE DAMAGED FOUNDATIONS FOUNDATION CONSTRUCTION TYPES FOUNDATION INSPECTION METHODS FAILURES by FOUNDATION TYPE & MATERIAL FAILURES by FOUNDATION MOVEMENT TYPE FLOOD DAMAGE TO FOUNDATIONS FOUNDATION DEFECTS OF OMISSION FOUNDATION CRACK EVALUATION FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION DAMAGE SEVERITY FOUNDATION DAMAGE REPORTS FOUNDATION INSPECTION STANDARDS FOUNDATION MOVEMENT ACTIVE vs. STATIC FOUNDATION REPAIR METHODS SITE FACTORS AFFECTING FOUNDATIONS SLAB CRACK EVALUATION WATER ENTRY in BUILDINGS ADDITIONAL READING More Information InspectAPedia TM Home & Site Map Air Conditioning InspectAPedia Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Bias Pledge Contact Us |
More Information on Building Diagnostic Inspections and Repairs
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08/05/2008 - 05/22/2007 - www.inspect-ny.com/structure/FloorCracks.htm - © 2008 Copyright Daniel Friedman All Rights Reserved