“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.

SECTION 305
PROTECTION OF PIPES AND
PLUMBING SYSTEM COMPONENTS

Stress and strain. Piping in a plumbing system shall be installed so as to prevent strains and stresses that exceed the structural strength of the pipe. Where necessary, provisions shall be made to protect piping from damage resulting from expansion, contraction and structural settlement.

“Foundation walls and retaining walls shall be designed to resist lateral soil loads from adjacent soil. Soil loads specified in Table 1610.1 shall be used as the minimum design lateral soil loads unless determined otherwise by a geotechnical investigation in accordance with Section 1803. Foundation walls and other walls in which horizontal movement is restricted at the top shall be designed for at-rest pressure. Retaining walls free to move and rotate at the top shall be permitted to be designed for active pressure.

Lateral pressure from surcharge loads shall be added to the lateral soil load. Lateral pressure shall be increased if expansive soils are present at the site. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1804.2 and 1805.4.3.”

Plumbing that is not designed to receive soil-induced loads can become unfunctional, crack, and become exposed to the subgrade.

Forces on slabs can cause damage too (before rod and nut punches through soil and support washers). If rod buckles, plumbing can be damaged.

Principle No. 9: The piping of the plumbing system shall be of durable material, free from defective workmanship, and so designed and constructed as to give satisfactory service for its reasonable expected life.

Principle No. 18: Where a plumbing drainage system may be subjected to backflow of sewage, suitable provision shall be made to prevent its overflow in the building.

Principle No. 19: Plumbing systems shall be maintained in a sanitary and serviceable condition.

Principle No. 22: Sewage or other waste from a plumbing system which may be deleterious to surface or subsurface waters shall not be discharged into the ground or into any waterway unless it has first been rendered innocuous through subjection to some acceptable form of treatment.

This item was proposed by the Structural Engineers Association of Texas (SEAoT) with a 14-page Rationale Statement. This statement was based on a review by a collaboration of structural, mechanical and geotechnical engineers of the state of the practice, recent litigation, a publication from the Foundation Performance Association, and various products on the market.

“In these instances [referring to Non-Isolated Void Systems], the Mechanical Engineers are relying on the Manufacturer’s claims as a proprietary product and not designing a system that includes these products. However, these products retain soil as they move in response to swelling and shrinking and they impart loads onto the structure and hangers that must be accounted for.

Many design approaches which use these products in an attempt to partially isolate plumbing may actually make matters worse than if the plumbing was simply buried, even though the manufacturers claim that the product will provide a void and some Owners spend money on these products with an expectation that these products will provide a complete void.”

The item was supported by the American Institute of Architects, the Geoprofessional Business Association, the American Council of Engineering Companies – Texas, and various mechanical, geotechnical and structural engineers. The item was approved at OGV with some floor modifications.

Explicitly requires protection of plumbing from expansive soil.

Allows buried pipe under slabs-on-ground.

Requires complete isolation of plumbing under crawlspace slabs and slabs-on-voidform: “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 crawlspaces

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

Requires “flexible expansion joints” in the plumbing at transitions to buried conditions outside of the building. (Note: Many building officials require access be provided to flexible expansion joints.)

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.