Out of Sight, Out of Mind: Underground Building Services

In property inspections, concealed and inaccessible components are frequently overlooked, despite representing some of the highest financial and operational risks. Underground building services—particularly sanitary sewer laterals and domestic water supply lines—are often excluded from standard inspections, yet failures in these systems can result in significant repair costs and site disruption.

A best practice during due diligence is to retain a licensed plumber to perform a closed-circuit television (CCTV) inspection of the sanitary sewer lateral. The inspection should document the condition of the piping from the main building stack through to the municipal connection at the property line. CCTV inspections can identify common defects such as longitudinal cracking, circumferential fractures, corrosion, scaling, bellies (sags), joint displacement, root intrusion, and partial or full collapses.

There is a common assumption that cast iron drainage piping is limited to residential buildings constructed prior to 1975. While this is often accurate for single-family dwellings, cast iron sanitary piping is still frequently encountered in commercial and multifamily properties constructed into the mid-1980s. Buried cast iron pipe typically has a service life of approximately 40 to 50 years, depending on soil conditions, pipe bedding, moisture levels, and wastewater chemistry. As corrosion progresses, wall thickness is reduced, leading to structural failure, leakage, and eventual collapse.

Vegetation located near the building perimeter is a strong indicator that underground piping warrants further evaluation. Many tree species possess aggressive root systems that actively seek moisture sources. Even minor defects at pipe joints or hairline cracks can allow root infiltration, which accelerates mechanical damage and blockage formation. Root intrusion is a leading cause of sanitary line failure in older installations.

The replacement of underground sewer laterals is a high-cost, invasive repair. Remediation may require open-cut excavation through finished basements, slab-on-grade floors, landscaping, driveways, or parking areas. In many cases, repairs involve coordination with municipal authorities and compliance with current plumbing and building codes, further increasing project complexity and cost.

Equally important is the evaluation of the underground domestic water service line. In older urban areas, including parts of Ottawa, lead service lines may still be present. These lines pose both health concerns and infrastructure risks. When lead or deteriorated steel supply lines fail, full replacement is typically required. This often involves excavation from the municipal shutoff to the building foundation, resulting in substantial restoration costs to the property.

To mitigate these risks, inspectors, buyers, and investors should adopt a structured inspection checklist when conducting walkthroughs and due diligence reviews. Systematically identifying concealed components and recommending further investigation where access is limited helps prevent unforeseen capital expenditures. Early identification of underground infrastructure issues also strengthens negotiating positions by providing clarity on potential major repair liabilities prior to closing.

In technical property evaluations, underground systems should be treated as critical infrastructure. What is hidden from view often carries the greatest long-term risk.