Building Officials, Plan Reviewers & Plumbing Inspectors

Some of the methods and devices which are discussed in this presentation are inventions by various parties and have been PATENTED or are PATENT-PENDING. These methods and devices are referenced in this presentation without naming the manufacturers. A primary purpose of referencing these methods and devices is to discuss the relative technical advantages and disadvantages of various approaches used in the industry today. This presentation is not an inducement to patent infringement. Therefore, this slide is hereby providing NOTICE to all attendees that attendees should assume all methods and devices discussed in this presentation are PATENTED or are PATENT-PENDING unless they verify otherwise. Attendees are welcome to contact the Presenters and request more information related to intellectual property for any specific methods and devices referenced, if desired.

Increase in moisture content Increase in volume (Swelling)
Decrease in moisture content Decrease in volume (Shrinking)

Geotechnical Engineers estimate heave using various methods
– Potential Vertical Rise (TxDOT method from the 1950s)
– Vijajvergiya & Ghazzaly (1973)
– several others

Soil shrink-swell is a four-dimensional phenomenon (L3 × T)

Depth of the “Active Zone” varies from site to site (e.g. 3 ft to 30+ ft)

“Expansive Soil” is defined by the IBC (2021 IBC Section 1803.5.3)

Beyond Expansive Soil

Examples of other types of volumetric soil changes:

• Settlement
• Frost Heave
• Collapsible Soils

Strategies that work for expansive soils often work for other geotechnical problems as well.

“On the advice of the forensic consultant, the client chose to excavate a deep crawl space under the building floor – essentially a basement – so workers could access the sewer lines and repair them. This labor-intensive effort cost
about $8.3 million*. Not surprisingly, the client filed construction-defect claims against all the design firms
involved, the constructor-in-charge, and the mechanical constructor. The client was seeking $25 million to pay for sewer-line repairs, floor-slab repairs, interior repairs, lost
revenue from residents, resident-relocation costs, attorney’s and expert’s fees, and court Costs.” *All financial factors are reported in 2020 dollars. Foundation approx. 100,000 sf

“The Member Firm agreed to a settlement two weeks before the trial; seven years after the client initiated the claim; and eleven years after the Member Firm initiated the project.”

>$1M Damage
at a High School

1/2” movement like this can
occur in Buried Pluming or
Non-Isolated Void Systems

Damage under Slab-on-Voidwork
to Non-Isolated Plumbing is likely
much more common that realized.

Cracked Plumbing

Backdraining Plumbing

If a design firm has $2M in errors and ommissions insurance and has to pay $25M in litigation for negligence, which was the amount of the claim in GBA Case Study 108, on a public work project where there is no limitation of liability, the insurance carrier would have to pay $2M and the design firm would have to pay $23M.

The typical defense for a specifying engineer is to show that they complied with applicable construction codes and practiced within the “standard of care”, as both are typically required in agreements defining an engineer’s scope.

If a lawsuit occurs years after plans are signed and sealed by an Engineer, it is difficult for a Judge or Jury to disregard changes that happened after the plans were signed and sealed. If engineers stop specifying non-isolated plumbing in the future, expert witnesses will testify that their opinion is non-isolated plumbing is not within the standard of care during the trial. Judges and Juries should not consider this testimony to be relevant, but it is hard for non-technical people to understand the distinction, especially as there is plenty of evidence today that non-isolated plumbing should not be specified under slab-on-voidwork foundations.

It’s hard to defend “saving” a Client $1/sf on construction costs when evidence like this emerges in the industry that the Client may have to spend $10/sf every few years in plumbing repairs (not including the costs of interrupting building function) over and over again. It just looks like engineering negligence to a Client after the damage occurs.

“Specification and Application of Void Spaces Below Concrete Foundations” by a Committee of the Foundation Performance Association in 2014 (with similar language in 2007)

3.7 CONSIDERATIONS FOR UNDER-SLAB UTILITIES

“Under-slab utilities should be carefully designed when Void Space is provided between the Slab Area and Grade Beams and the soil. Expansive Soil should not support under-slab utilities below an Isolated Slab on an Isolated Foundation. Under-slab piping must remain stationary with respect to the Slab Area.”

In November 2021, GBA issued a recommendation to its thousands of
Geotechnical Engineers across the country that Geotechnical Engineers explicitly
recommend isolation of plumbing under Slab-on-Voidwork in their soil reports.