How to Recognize Foundation Defects of Omission - things left out InspectAPedia® -
How to Recognize Foundation Defects of Omission - things that were omitted that later lead to foundation damage, cracks, settlement, movement, leaks
Visual inspection of foundations
Types of foundation damage
Photographs of foundation damage patterns
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This document describes
Missing foundation footings and other foul ups - How to Recognize Foundation Defects of Omission - things that were omitted that later lead to foundation damage, cracks, settlement, movement, leaks and
other problems. Our page top photo shows a pre-fab concrete and wood foundation which has been installed over no footing and no backfill (yet). Is this a problem?
4. FOUNDATION DEFECTS OF OMISSION - Identify Foundation Defects of Omission, things that were left out or forgotten during foundation construction
Construction defects of omission refers to leaving out or removing necessary structural
components.
It is considerably more difficult for a building inspector to learn to observe
the absence of a component than to notice defects involving a component which is present.
This brick veneer wall was constructed over a masonry block structural wall; the veneer contained no expansion joints though some of its sections were nearly 100' in length.
The cracks visible in this photograph had that omission as their root cause.
Northridge Earthquake Building Collapse - Check out These Supporting Columns
Here are examples of types of omission that contributed to a structural collapse. During our work at the Northridge Earthquake site in California in 1994 we noticed that some of the supporting Lally columns were hollow rather than concrete filled.
Perhaps due to material shortages or rush during construction, these hollow, and weaker supporting columns were wrapped with a fire-barrier just as were the "real" supporting columns used elsewhere.
Our photos show a section of Northridge Meadows which collapsed during the earthquake. At left you can see that this column was hollow.
Our opinion was that these were defective columns and that they were a factor in the structural collapse during the Northridge earthquake. Other areas of the same complex moved, columns even leaned, but they did not collapse where the columns were of the proper type and were properly connected to the structure.
Other factors in the collapse appeared to include how exterior sheathing had been nailed across or not across certain sections of the building supporting walls. Our list of examples of defects of omission during foundation construction continues below.
Missing footings (may or may not be a defect depending on design and soil conditions)
Missing supporting columns such as a basement Lally column, where an owner has removed the column
to open up a basement space being remodeled for use as living area
Omitted steel reinforcement - footings missing re-bar or other required steel rods (not visibly detectable after construction)
Omitted steel reinforcement - walls missing steel reinforcing wire or re-bar (possibly visibly detectable after construction if cracks permit view into wall structure)
Missing piers beneath interior or exterior posts (may be visible as post settlement)
Missing control joints in poured concrete slabs, concrete floors where random shrinkage cracks appear
Missing expansion joints in large or long brick masonry walls both in structural brick walls and in brick veneer walls, where thermal expansion cracking occurs (see photograph above)
Missing expansion joints/materials around windows or doors in poured concrete or brick masonry walls may appear as damaged or inoperable windows or doors.
Failure to compact the soil under a foundation footing or under a poured concrete slab which has been placed on backfill
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Additional technical contributors & reference sources for this article are listed below.
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"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
"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
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