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STRUCTURAL INSPECTIONS & DEFECTS
AGE of a BUILDING - how to determine
BRICK FOUNDATIONS & WALLS
BRICK STRUCTURAL WALL Loose Bulged
BRICK WALL THERMAL EXPANSION CRACKS
BRICK WALL DRAINAGE WEEP HOLES
BUCKLED FOUNDATIONS due to INSULATION?
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLD POUR JOINTS, CONCRETE
COLUMNS & POSTS, DEFECTS
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
FRAMING DAMAGE, INSPECTION, REPAIR
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
SLAB CRACK EVALUATION
SLAB CRACK REPAIR
STRAW BALE CONSTRUCTION
STRUCTURAL DAMAGE PROBING
STRUCTURAL WOOD ASSESSMENT
THERMAL EXPANSION of MATERIALS
TIMBER FRAMING, ROT
WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
This article presents a case study by Bob Maltempo, P.E. with comments by Daniel Friedman. The case demonstrates the inspection, detection, diagnosis, and repair repair recommendations regarding structural damage (or none) to a building foundation wall and floor slab following flooding.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Fine vertical or near-vertical cracks in a masonry block foundation may be caused by shrinkage in the concrete blocks - a condition that occurs shortly after construction. Shrinkage cracks in masonry tend to be uniform in width, top to bottom, but might be more narrow at the crack bottom where the masonry blocks are pinned to a (presumably not shrinking) footing.
Fine vertical or near-vertical cracks in a concrete block wall may also be caused by footing settlement. If that cause is present, careful measurement should find that the wall is not at exactly the same height on both sides of the vertical crack.
Floodwaters around a building, if they press principally on only the wall exterior, can cause a wall to buckle, bend, or lean inwards. These pressures often cause horizontal cracking in a masonry block wall; vertical cracks would be unusual. That pattern of movement was absent from this home.
How would a flood cause a vertical crack in a masonry block foundation wall? Floodwaters or even wet soils around a building might cause footing settlement, particularly in a newer building whose footings may have been placed on poorly-compacted soil. That pattern of movement was also absent from the home.
Since floodwaters would be expected to surround a home built on a relatively flat lot, one would also seek to determine why only one wall of the building was affected. There could be explanations for that asymmetry.
Our opinion was that the cracks in this masonry block wall were chiropractors of masonry block shrinkage, that they were most likely caused by that effect and not caused by flooding.
Cracks in a Garage Floor Slab - Caused by Flooding?
Damage and Risk Assessment of Wall & Floor Cracks:
The first priority question is whether or not there is evidence that the cracks observed represent damage to the building that needs repair - that is, are the cracks cosmetic or are they more important. In the case above there was no evidence of structural movement in the foundation wall and the cracks about 1/16" wide, vertical - a low-threat to foundation walls. The garage floor was not a structural element (it is not carrying the structural loads); a cracked concrete floor slab might however be considered a trip hazard if cracks are higher on one side than the other by 1/8" or more, and in some areas floor slab cracks can increase the risk of radon gas entry or water entry.
How is the foundation wall constructed?
In the case we describe, as in most older homes, the concrete wall is constructed without internal reinforcement, placed on a poured concrete footing (not visible, but assumed).
Questions about Possible Flooding as a Foundation Damage Cause or Contributor
Comments About Building Foundation Cracking & Building Flooding
Vertical cracks in a masonry block wall are usually from initial shrinkage, and they usually occur near the center of the wall, are fairly uniform in width, and may taper to a more narrow width or no crack at all close to the foundation footing where the footing, particularly if pinned to the wall bottom, holds the bottom of the wall in place.
Vertical cracks in a concrete block wall are usually a low-threat to the structure (if at all) unless the cracks can be tracked to ongoing and/or significant footing settlement, foundation leaning or tipping.
Vertical cracks in the center of a concrete block wall due to earth pressure or flood water pressure would be unusual. Usually this pressure finds it easier to break the concrete block courses at the mortar joints, producing horizontal cracking; If there is significant wall buckling (see page top photo) step cracks may also appear in the block wall. In a severely bowed concrete block wall the classic pattern is wide horizontal cracks in mortar joints the middle or lower wall leading to step cracks in the mortar joints closer to the wall corners.
Questions About Concrete Slab Floor Cracks and Flood Damage
What is the crack pattern in the slab (breaking vs. shrinkage, for example) and where in the slab do cracks occur (at corners, near a garage entry door, around Lally columns?)
Comments about New & Old Cracks in Floor Slabs & Wire Brushed Cracks
New Versus Old Foundation or Slab Cracks
Often we find that a long-standing condition at a building is perceived as new by an owner or occupant only after it has been called to their attention for the first time. A person's anxiety about the newly-observed feature (mold, stains, cracks) can increase their certainty that the phenomenon is a new one even if forensic evidence of the age of the condition is compelling.
Frequently Asked Questions (FAQs)
Questions & answers or comments about how to assess building foundation damage from flooding
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Technical Reviewers & References
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