Who is responsible for ensuring a successful waterproofing design—the architect or the contractor? Obviously, this is a broad question that ignores the wide range of design, specification and/or management responsibilities carried out by architects throughout North America. Yet, this simplistic query highlights a theme that recurs constantly during the construction defects litigation resulting from ineffective weatherproofing:

  • The contractor blames the architect’s minimal detailing.
  • The architect argues that the contractor is the construction expert responsible for implementing the project’s ‘design intent.’
  • The contractor responds that he/she bid the project per the architect’s minimal details and specifications and that the project’s funding limits prevented any upgrades to this design.
  • The architect then asserts that no matter how tight the funding he/she certainly would have approved a written change order for improved flashing or waterproofing if the expert contractor had only emphasized its importance.

At this point, both parties may storm out of the meeting.

In many cases, both the architect and contractor must share a varying degree of responsibility for failed waterproofing. The contractor should have sufficient understanding of flashing and waterproofing methodology to be able to evaluate the adequacy of the architect’s details and specifications. In very general terms, his failure to provide written notice of an inadequate design and his continuation of the work constitutes an acceptance of responsibility for ensuring satisfactory performance of the building envelope. Yet Section 106.3 of the International Building Code (IBC) burdens the architect with the primary level of design responsibility: “The construction documents shall provide details of the exterior wall envelope as required, including flashings, intersections of dissimilar materials, corners, end details, control joints, intersections and roof, eaves or parapets, means of drainage, water-resistive membrane and details around opening.”

A Few Practice Examples

Consider, for example, the comprehensive Stucco Resource Guide published in Seattle by the Northwest Wall and Ceiling Bureau. It is not uncommon for Pacific Northwest architects to simply specify that the stucco application must comply with NWCB standards and details; however, this action begs the question of who is responsible for project-specific detailing of unusual building transitions not addressed within the Stucco Resource Guide. The architect? The contractor? Should we just leave such decisions to the whims of the stucco applicators up on the scaffolding?

In 2005, for multi-unit residential buildings only, the Washington State legislature answered these questions of overall responsibility for the weatherproofing design. Consistent with the intent of Section 106.3 of the IBC, House Bill 1848 requires that the construction drawings submitted to the local building official must include a complete packet of waterproofing details “that have been stamped by a licensed engineer or architect.” Further, the project architect or engineer must submit a written statement confirming that in his/her “professional judgment” these submitted details and specifications are appropriate to fully “waterproof, weatherproof and otherwise protect the building or its components from water or moisture intrusion . . . “

In addition, HB 1848 requires that, during construction of multi-unit residential buildings, there must be “independent periodic review of the building enclosure” by a “qualified building enclosure inspector” who “may not be an employee, officer or director, nor have any pecuniary interest in the declarant, developer, association or any party providing services or materials for the project, or any of their respective affiliates, except that the qualified inspector may be the architect or engineer who approved the building enclose design documents or the architect or engineer of record.”

  In essence, the Washington State legislature has decreed that the building contractor who consistently complies with the project’s waterproofing and flashing details (as stamped by a licensed architect or engineer) and any supplemental course-of-construction guidance provided by the required independent inspector will not be the prime target if leakage and mold problems later occur.

In our experience, there are many architects and engineers who are well qualified to evaluate, detail and specify even the most complex flashing, cladding and roof covering systems. Similarly, there are many contractors whose roofing and waterproofing skills and dedication to quality construction are exemplary. Nonetheless, most architects, engineers and contractors are not roofing or waterproofing experts. For building professionals in those many states and jurisdictions where there is not a strong delineation of who is responsible for the building envelope design, we offer the following guidance that can greatly reduce their risks of becoming fully embroiled in leakage and mold litigation:

Defining Weatherproofing Protection

The first step for all parties is to identify who is the ‘responsible professional in charge’ of the building’s weatherproofing design.

  For most projects, the sensible course of action for the owner and architect is to hire an independent waterproofing design professional to review (and often supplement) the architect’s original details and to carry out representative inspections of the construction. If the building envelope later fails, it is the waterproofing design professional who has the huge target on his/her back—not the architect.

For contractors, there are two critical steps they can take to protect themselves. First, fully implement the building envelope design that has been specified and detailed by the architect. If such weatherproofing specifications and details are found to be incomplete, always request written guidance from the designer. Time after time, we see projects where a well-intentioned contractor, worried about keeping the project on schedule, decided to simply “fix” an insufficient waterproofing design. By this simple action, he not only is taking responsibility for the long-term effectiveness of that “fix”, but is also informing future attorneys that he is a skilled waterproofing professional willing to accept a great deal of responsibility for the effectiveness of the entire waterproofing design.

Secondly, keep a written daily log. In particular, summarize all discussions and verbal directives from the owner, architect and other design professionals. Often, it is simply the contractor’s poor recordkeeping that allows the opposing parties to make him the scapegoat for bad decisions made by others. This daily log need not be lengthy; it simply needs to document the day-to-day actions by others that affect the project’s weatherproofing design and its course of construction. In addition, the contractor must save these records, even if they are nothing more than ragged slips of paper stored in shoeboxes at the back of a closet. Far too often, project records are thrown away prior to the end of the period when a construction defects claim can be initiated. This hastiness can prove to be a very costly error.

In summary, when a building leaks, typically everyone involved with its design and construction gets sued. Eventually, the biggest losers are those who keep the worst records and those who by their actions or inaction became responsible for the performance of the as-built weatherproofing design. The best interests of all parties are served by hiring a waterproofing professional to accept the mantle of responsibility imposed by the IBC.

February 2007
Issue Two, Volume Two

This article by Colin Murphy and Lonnie Haughton.

Colin Murphy
Murphy is a founder and managing partner of Trinity | ERD.

Lonnie Haughton
Haughton is a construction codes and standards consultant with Richard Avelar & Associates.


Mold and Moisture Management Magazine Archives


Read House Bill 1848


NWCB - Stucco Resource Guide


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"Pushing the Envelope: A Monthly Journal of Issues Concerning Building Design, Science, and Litigation" is a monthly publication of Trinity | ERD. This newsletter is intended as a thoughtful look into the issues of building construction.

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