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HORIZONTAL CRACKS
Causes:
The vast majority of horizontal cracks are caused by rusting of the horizontal rebar in the foundation. The most common causes are (a) insufficient concrete cover (i.e. rebar placed too close to edge of the concrete) or (b) salt from leaking water softener. A less common cause is (c) when neglected vertical cracks allow atmosphere to reach the horizontal rebar.

Avalon's Promise:
The proper repair of horizontal cracks, per the International Concrete Repair Institute (ICRI) and the American Concrete Institute (ACI), is to repair or replace the rebar and replace the damaged concrete. Avalon repairs horizontal cracks in compliance with the ICRI and ACI codes. Additionally, our work on horizontal cracks is always designed and certified by an independent engineer.

Improper Shortcut:
Some contractors cheaply shortcut this process to reduce costs and increase profit. Such contractors attempt to repair such damage with glued-on fabric, aka Carbon Fiber, or epoxy injection. However, the root cause of the crack very likely remains. The rusting rebar is compromised and may continue to expand and further damage the foundation. Please note that Carbon Fiber and Epoxy Injection are each amazing solutions for some problems in the world of concrete repair - but neither are appropriate for horizontal cracks in foundations unless as part of complete solution certified by an engineer.

Horizontal Crack Example:
The rusted rebar is generally hidden inside the horizontal crack. Sometimes the rusting rebar is visible, as shown in this photo. Very likely, the cause was insufficient concrete cover with the rebar placed so close to the edge of the concrete.

Avalon would chip away the concrete to fully expose the rusted rebar and following best practices replace rusted rebar and the replace the concrete.
From ICRI Guideline Number 302.2R-2009 (emphasis added)

Sec.2.1 The practice of completely removing the concrete (undercutting) from around the corroded reinforcement, no matter what degree of corrosion is found, is key to achieving long-term performance of surface repairs. In most cases, complete removal of the concrete from around the reinforcing steel is the best practice, where protection of the reinforcing steel within the repair cavity is achieved by providing a uniform Chemical environment around the reinforcing steel. ...

Sec. 2.4 Concrete removal should extend along the reinforcing steel until there is no further delamination, cracking, or significant corrosion and the reinforcing steel is well bonded to the surrounding concrete. ...

Sec. 2.5 If reinforcing steel has lost cross-sectional area, a structural engineer should be consulted. Repair reinforcing steel by either replacing the damaged/deteriorated steel or placing supplemental reinforcing steel in the affected section. ...

Sec. 2.7 The repair of deteriorated concrete resulting from reinforcing steel corrosion is necessary to extend the service life of the structure. Performing concrete repairs using industry-best practices will ensure the success and longevity of the repair. Understanding the existing conditions and cause of corrosion will assist the engineer in specifying the type and extent of the repair required ...
Note: Beware Loopholes, Fine Print, and Frauds
Some contractors treat all horizontal cracks as if they are "pop-outs", chipping only a few inches into the concrete. This is a superficial approach and drastically saves on costs by eliminating or reducing: shoring, difficult demolition, breaking, loading and hauling of the removed foundation, setting forms, and placing new concrete. To the best of our knowledge these contractors do not involve engineers in the project, as no conscientious engineer would certify this approach.

One particularly egregious case is a local contractor that slides into their contract a loophole stating they will abandon the search for rebar if none is found within three inches of the crawlspace side of the wall. As if walls only have one side! They offer engineering "if necessary", presumably leaving it to a laborer to make the call. Despite representing they will replace rebar, fine print states "No rebar replace. Epoxy and carbon armor." Please read the fine print and compare it our fine print!
Avalon Structural, Inc.
181 Ridgeview Drive
Aptos, CA 95003
(831) 479-4389 (office)
info@avalonstructural.com
Copyright © 2020
Avalon Structural, Inc.
All Rights Reserved
CA License 677116
Classifications:  B, C-8
Avalon is a general building
contracting firm and
does not employ engineers.