The 2024 International Plumbing Code (IPC) will have new language explicitly requiring isolation of plumbing from expansive soil under isolated slabs (over a crawlspace or voidwork). It will not permit buried plumbing. It will also not permit non-isolated void systems that provide various forms of “voids” but do not actually isolate plumbing, hangers and supports under the slab, even though the manufacturers may claim they “isolate” plumbing. Furthermore, as a consequence of many lawsuits and the clarifying language in the 2024 IPC, Mechanical Engineering firms today are increasingly interpreting long-standing IPC requirements for protection of plumbing to require isolation of plumbing from expansive soil under isolated slabs. Below isolated slabs, these firms are not allowing buried plumbing and not allowing non-isolated void systems.

For Example

BHB’s current office policy is to consider the new 2024 IPC language to have already taken effect as a clarification of current plumbing codes by the International Plumbing Code Committee (the “IPC Committee”).

BHB will no longer allow buried plumbing under crawlspaces or voidwork.

BHB will no longer allow “non-isolated void systems” under crawlspaces or voidwork.

Mechanical Engineers cannot isolate plumbing without Structural Engineers doing their part. Responding to recent changes in Mechanical Engineering practices that define the Mechanical Engineering standard of care, this presentation will identify tasks for Structural Engineers.

TASK #1: KNOW WHAT ISOLATED PLUMBING IS

TASK #2: UNDERSTAND THE PROBLEM

TASK #3: LET THE GEO ENG BE THE GEO ENG

TASK #4: LET THE MECH ENG BE THE MECH ENG

TASK #5: DO THE STRUCTURAL ENGINEERING

Intellectual Property Notice

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.

For Example

For many years, Alpha Testing has recommended a voidspace under plumbing under isolated slabs where expansive soil is present. However, non-isolated void systems circumvent the intent of Alpha’s previous recommendations by providing a void but not isolating the plumbing. Given this concern and the clarification in the industry provided by the IPC Committee, Alpha has revised its template recommendations to be consistent with the new, clarifying language in the 2024 IPC and the recommendations of other organizations such as the Geoprofessional Business Association.

Building Professional Institute (BPI)

The new 2024 IPC language was presented at the North Texas BPI in a 3 hour presentation in July 2022. Furthermore, because all previously published editions of the IPC and UPC require protection of plumbing to avoid overstressing and overstraining pipe material, the BPI presenters recommended Mechanical Engineers “immediately cease and desist the practice of permitting Non-Isolated Plumbing (Buried Plumbing or Non-Isolated Void Systems) under Slab-On-Voidwork foundations…”. The slides and the video are available for download from BPI.

All 3 presenters of this SEAoT Dallas presentation today agree with the content and recommendations presented at the North Texas BPI Presentation by those 3 engineers. Their 3 hour presentation is the most comprehensive review of this issue in the industry today. We encourage you to download that content from the BPI website and evaluate your office policies in consideration of that content. The slides and the video are available for download through BPI online at www.bpi-tx.com

First, know what we mean when we say ISOLATED SLABS.

Isolated Slabs:
Slab-on-Crawlspace

Isolated Slabs:
Slab-on-Voidwork

Second, know the difference between what we mean when we say ISOLATED plumbing versus NON-ISOLATED plumbing.
Many Mechanical Engineers and Manufacturers are claiming that various approaches or products “isolate” plumbing when they actually do not.

Isolated Slabs with Non-Isolated Plumbing

Regardless of how manufacturers may claim that their connections will flex or slip if soil movement occurs, these systems do not completely “isolate” plumbing, hangers and supports below the slab from all soil-induced loads.

Examples of Non-Isolated Plumbing

Note: These are examples of PATENTED methods and systems.

Examples of Non-Isolated Plumbing

Note: These are examples of PATENTED methods and systems.

Isolated Slabs with Isolated Plumbing

Examples of Isolated Plumbing

International Plumbing Code
New Language in the 2024 Edition

Explicitly requires protection of plumbing from expansive soil and defines when expansive soil is present.

Allows buried plumbing under Slabs-on-Ground.

Requires complete isolation of plumbing under Slab-on-Crawlspace and Slab-on-Voidwork: “It shall not be permitted for the plumbing, hangers and supports below the slab or below the framing to be in contact with soil or any assemblage of materials that is in contact with soil within the active zone.”

Exception 1 allows buried pipe for drainage of crawl spaces

Exception 2 allows attachment to piers if the plumbing, hangers and supports are otherwise isolated.

305.8 Expansive Soil. Where expansive soil is identified under buildings in accordance with Section 1803.5.3 of the International Building Code, but not removed in accordance with Section 1808.6.3 of the International Building Code, plumbing shall be protected in accordance with Section 305.8.1 or 305.8.2.

305.8.1 Non-Isolated Foundations. Under foundations with slabs that are structurally supported by a subgrade, it shall be permitted for plumbing to be buried.

305.8.2 Isolated Foundations. Under foundations with a slab or framing that structurally spans over an under-floor space which isolates the slab or framing from the effects of expansive soil swelling and shrinking in accordance with Section 1808.6.1 of the International Building Code, the plumbing shall be suspended so that plumbing, hangers and supports are isolated, by a voidspace, from the effects of expansive soil swelling and shrinking.

Exception: It shall be permitted for plumbing to be buried if the plumbing provides drainage of an under-floor space.

To protect the voidspace, soil shall be sloped, benched or retained in accordance with an approved design methodology.

It shall not be permitted for the plumbing, hangers and supports below the slab or below the framing to be in contact with soil or any assemblage of materials that is in contact with soil within the active zone. It shall not be permitted for a slab and plumbing to be lifted as an assembly to create the voidspace unless the under-floor space is a crawlspace with access to allow inspection of plumbing after lifting.
Exception: It shall be permitted for the piping, fittings, hangers, and supports below the slab or below the framing to be in contact with structural elements of the foundation that are designed to resist the effects of expansive soil swelling and shrinking in accordance with Section 1808.6.1 of the International Building Code.
Organic materials subject to decay shall not be used for hangers, supports and soil retention systems. Materials subject to corrosion shall not be used for hangers, supports and soil retention systems unless protected in an approved manner.
Where plumbing transitions to a buried condition beyond the perimeter of the foundation, an adequately flexible expansion joint shall be provided in the plumbing system to accommodate the effects of expansive soil swelling and shrinking.

Third, know that isolated plumbing is not protected if the transitions to non-isolated plumbing at the perimeter are not protected.

Isolated Slab with Isolated Plumbing
and a Protected Perimeter Transition

Note: This is an example of a PATENT PENDING method.

The following slides illustrate examples of Expansive Soil Behavior under Isolated Slabs

General Under-Slab Settlement

General Under-Slab Swelling

Perimeter Under-Slab Shrinkage

Perimeter Under-Slab Swelling

Localized Under-Slab Settlement

Localized Under-Slab Swelling

Complex Swelling & Shrinking

Federal Court Ruling re Isolated Slabs and Non-Isolated Plumbing

“The Government claims that BPLW provided a negligent underfloor piping design, as the design failed to accommodate the “highly expansive” soils in the San Antonio area.” “The Government contends that these negligent designs caused the piping problems at the dorms and led it to incur substantial expense to repair broken pipes, replace the underfloor piping system, and remedy the site grading.”

“As set forth below, the Court finds that BPLW did indeed provide negligent underfloor piping and civil site grading designs, as both failed to comply with the contract requirements and the applicable standard of care.”

BPLW ARCHITECTS & ENGINEERS, INC. V. THE UNITED STATES
IN THE UNITED STATES COURT OF FEDERAL CLAIMS
NO. 09-672C (FILED: SEPTEMBER 7, 2012)

GBA Case Study re Isolated Slabs and Non-Isolated Plumbing

“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.”

Examples of Litigation reported in the News re Isolated Slabs and
Non-Isolated Plumbing

Examples of Damage with Slab-onVoidwork and Non-Isolated Plumbing
With only 1/2” Vertical Movement

Examples of Repairing Non-Isolated Plumbing under an Slab-on-Voidwork after only 1/2” Vertical Movement (>$1M)

This repair simply replaced cracked plumbing in a non-isolated condition, so damage is expected to occur again.

Examples of Plumbing Damage under Slab-on-Crawlspace where Plumbing
Transitions to Non-Isolated Plumbing

The 160 slides of the BPI Presentation go into great detail on Non-Isolated Plumbing approaches under Isolated Slabs:
– How Non-Expansive Trench In-Fill and/or Vertical Sleeving through an Isolated Slab does not solve the problem.
– How Mechanical Engineers are specifying Retaining Walls in Non-Isolated Void Systems without the Structural Engineering education and experience required by Texas Engineering Practice Act (TEPA).
– How Complex it would be to design a Hanger Rod (partially in expansive soil undergoing volumetric changes) for Expected Uplift.
– How Mechanical Engineers have a false sense of security because they normally specify labelled and listed products but they have been misled by Non-Isolated Void System Manufacturer’s claims about these unlabelled and unlisted products, and a TEPA provision which allows unlicensed staff at manufacturing companies to call themselves “Engineers”.
– How soil-retaining elements are required by the IBC to be designed for expansive soil swell pressures, which can be 100 times the structural limit states capacity of non-isolated void system components.
– How non-isolated plumbing imparts loads onto slabs that the Structural Engineer must account for in the design.

The following are some sketches from the BPI Presentation, to help illustrate the problem.

BURIED PLUMBING

BURIED PLUMBING
Installed Conditions

BURIED PLUMBING
General Under-Slab Settlement

BURIED PLUMBING
General Under-Slab Swelling

BURIED PLUMBING
Perimeter Under-Slab Swelling

BURIED PLUMBING
Complex Under-Slab Swelling & Shrinkage

MESH & PLYWOOD UNDER PLUMBING

MESH & PLYWOOD UNDER PLUMBING
Installed Conditions

MESH & PLYWOOD UNDER PLUMBING
Gen. Under-Slab Settlement

MESH & PLYWOOD UNDER PLUMBING
Decomposed Plywood

MESH & PLYWOOD UNDER PLUMBING
Gen. Under-Slab Swelling

MESH & PLYWOOD UNDER PLUMBING
Perim. Under-Slab Swelling

PLASTIC SIDE PANELS AND CROSSBARS

PLASTIC SIDE PANELS AND CROSSBARS
Installed Conditions

PLASTIC SIDE PANELS AND CROSSBARS
Gen. Swelling, No Rod Buckling

PLASTIC SIDE PANELS AND CROSSBARS
Gen. Swelling, No Rod/Crossbar Buckling

PLASTIC SIDE PANELS AND CROSSBARS
Settlement/Shrinkage

NET HORIZONTAL FORCES

Soil swelling on one side of a Non-Isolated Void System can create net horizontal forces that push Non-Isolated Void Systems and damage plumbing.

SWELL/SHRINK CYCLE DEFORMATIONS

Designers need to also carefully consider the effects of swell/shrink cycles on the deformed shape of non-isolated void systems.

In summary, the problem is that an unprecedented and possibly unobtainable level of inter-disciplinary testing and design coordination, plan review and plumbing inspection would be required on each project between the Geotechnical, Mechanical and Structural Engineer to properly protect plumbing using non-isolated plumbing approaches that have been used. A Plumbing Inspector does not have the ability to verify this occurred.

Expansive Soil is Challenging to Predict

Geology Matters
Site History Matters
Weather Conditions Matter
Groundwater Matters
Soils Are Anything But Uniform
Estimating Soil Movement To The Nearest One Inch Is, At Best, Challenging (And Estimates To The Nearest Quarter Inch May Be A Fool’s Errand.)
Expansive Soil Swell Pressures Can Exceed 20,000 psf.
There is always the potential for volume change to occur under a slab if expansive soil is present. The probability of movement occurring will never be zero.

The Geotechnical Engineer on the project is the expert on:
Geotechnical Engineering Standard of Care
Estimating Potential Vertical Movements
Estimating Potential Horizontal Movements
Estimating Expansive Soil Swell Pressures
Analyzing the Stability of Sloped and Benched Cuts
Estimating the Probabilities of Soil Movement Occurring

The Geotechnical Engineer on the project is not the expert on:
Mechanical Engineering Standard of Care
IPC Requirements for Protection of Plumbing
Structural Engineering Standard of Care
IBC Structural Material Strength Provisions

Compliance with Plumbing Codes is 100% the Mechanical Engineer’s responsibility, not the Geotechnical Engineer
Structural Engineers should not mislead anyone into thinking otherwise (Owners, Building Officials, General Contractors, Attorneys).
A Mechanical Engineer should not consider any Geotechnical Engineering recommendations regarding plumbing design considerations as the Geotechnical Engineer taking responsibility for the plumbing design on a project.

Attorneys representing Owners who indicated during design that they accepted the risks associated with high maintenance costs to benefit from lower construction costs often claim that uninformed Owners were misled by negligent design professionals. To maximize the amount of insurance money available to their clients, these Attorneys will often strategically claim many different design professionals were negligent…because the more firms accused means the more insurance money available.

Make it clear in your words and your documentation that the Mechanical Engineer ALONE is responsible for defining the design requirements to protect plumbing from expansive soil. And, SUPPORT them in this role by taking their lead on however they interpret plumbing codes and performing whatever Structural Engineering they require for it be protected.

Some Owners have questioned Mechanical Engineering firms that have changed their policies to require isolated plumbing under isolated slabs. Most Owners are more familiar with non-isolated plumbing and they perceive that the change will cost them a lot more money (which is not necessarily true).

However, litigation history indicates Owners routinely claim after the fact that they did not understand and accept the risk that the Mechanical Engineer thought the Owner was accepting. This is a public health, safety and welfare issue and it is in the best economic interests of Owners overall. When Mechanical Engineers have stood their ground on their office policies, Owners have ultimately respected the Mechanical Engineer’s integrity. In other words, Mechanical Engineers are being TESTED by Owners to see if it’s truly a requirement or not.

It is not helpful for the Structural Engineer or others to share anecdotal experiences about what the Structural Engineer perceives to be successful plumbing history with various approaches.

The evidence shows that these plumbing problems exist long before Owners become aware of them and Owners often mistake the cause of the problem to be something other than expansive soil movement until Attorneys become involved.

Some of the Structural Engineering items often required for Isolated Plumbing under Isolated Slabs:

+ Specifying benched cuts and/or retaining walls under Slabs-on-Voidwork where the voidwork bears on the subgrade of the utility trenches

+ Specifying that utility trenches be excavated by the Concrete Subcontractor where voidwork is placed on these trenches

+ Specifying voidwork be configured around isolated plumbing and installed by the Concrete Subcontractor with the main layer of voidwork

+ Specifying a structural element (e.g. gradebeam) that is connected to the isolated foundation for the Mechanical Engineer to specify attachment of the plumbing to the foundation at flexible expansion joints

+ Specifying concrete vaults, where required by the Mechanical Engineer to house flexible expansion joints, to be attached to and a part of the isolated foundation, with a vertical slotted opening at the elevations provided by the Mechanical Engineer for non-isolated plumbing