Roofing problems

Two causes, not one

Forensic investigators separate a design defect, meaning the plans themselves were wrong, such as a roof structure sized for the wrong load, from a workmanship defect, meaning the plans were fine but the crew that built it did not follow them. The distinction matters because it usually points to a different responsible party, and sometimes a different insurance policy.

"A design error means the drawings themselves were wrong, a beam undersized, a connection detail that never accounted for real loading."

Source: Common Construction Defects, Prema Consulting Group

In practice, a single failed roof often has both problems at once. One forensic review of a failed condominium roof found that the roof and the surrounding building envelope were designed with fundamental flaws, and that poor workmanship by the roofing contractor made the outcome worse.

"Fundamental problems with the roof design and the building envelope design, all of which were exacerbated by poor workmanship by the roofing contractor and perhaps pressures from the developer."

Source: Analysis of a Roof Failure, Roof Consultants Institute, archived by the National Roofing Contractors Association

In that case, parts of the roof had already begun failing before a windstorm drew attention to the problem. Do not assume a storm caused the damage just because it exposed it.

Where roofs actually fail

A roof is part of the building's envelope, the system that separates conditioned interior space from the outside. Practitioners who investigate water intrusion report that leaks concentrate at a small share of the surface, at seams, flashings, and penetrations, not across the open roof field.

"Ninety percent of all water intrusion problems occur within 1 percent of the total building exterior surface area."

Source: IIBEC Interface, IIBEC

This is a widely repeated estimate from experienced practitioners, not a measured statistic from a standards body, but it points a board toward where to look first: chimney flashings, vent penetrations, parapet caps, and the edges where a roof meets a wall. See Building envelope failures for the same pattern applied to walls.

What the board should do

Do not diagnose a roof failure yourselves, and do not assume the roofer's own explanation is complete. A forensic engineer or roofing consultant works from the project's design documents, a site inspection, and often material testing, to trace a failure back to its actual cause. See Expert investigations for what that process looks like.

If a leak is active and causing ongoing damage, address the safety issue first. But if litigation looks likely and there is no immediate hazard, get advice before repairing or altering the roof. See Preserving evidence.

Whether your state requires notifying the roofer and offering an inspection before suing, and how long you have to file a claim, varies by state and by claim type. Confirm your state's requirements and your governing documents before taking any action that could change the roof's condition.

For accepted roofing practice beyond what a single lesson can cover, the National Roofing Contractors Association's roofing guidelines are a standard industry reference.