December 2020 – Law and Civil Engineering

Go Back


The Details Matter
by Eugene Bass

Engineers who have been involved with condominium litigation know that a very common problem that most often precipitates the lawsuit is moisture intrusion. The structure leaks and it should not. Decks and wall penetrations are commonly sources of leakage. Flashing design and construction as well as integration of the waterproof membranes is necessary to prevent leakage. Some areas of the construction are difficult locations to achieve watertight construction. Under the door threshold and above the deck is a common problematic area to waterproof because of the narrow space left to avoid a large step between the deck and the inside. If the waterproofing is not effective in that area, and if the deck is not sufficiently sloped, leakage can occur.

In areas of a structure where it will be difficult to get an effective integration between flashing and the waterproof membrane, a watertight assembly will depend upon the level of detail shown on the plans and the skill, experience and integrity of the contractor in dealing with the particular installation. I recall one site visit with a client where the exterior of the building was completed to the point were the waterproof membrane was installed but the siding had not yet been placed. I noted an area where the membrane was just jammed into place with no apparent regard to proper lapping where water would run down the outside rather than into the structure. I asked my client “why did they do that as it is so obviously wrong?” My client told me “Gene…they just don’t care…” That was a disaster waiting to happen that derived from construction.

There have been other situations where the proper design of waterproofing, flashing and membrane integration was complicated and critical if an effective waterproofing assembly was to result. Such situations often occurred where there were interesting and unusual building shapes involving a variety of textures and building materials and that were not a typical gabled roof box construction. The problems with this type of structure were that there were many junctures that required specially shaped flashing and membrane integration so that effective waterproofing would result. The typical workman and contractor, left to his own imagination and experience may not have been able to produce an effective assembly, couldn’t afford the time or “just didn’t care.” In those instances, it is the architect who should carefully and clearly detail every critical juncture so that the contractor knows how to build an assembly that does not leak. Many times, all that the plans show are “typical details” that are virtually worthless for purposes of showing a waterproofing detail of an “non-typical” or unusual juncture.

The bottom line is that the designer should carefully and clearly detail all critical flashing and membrane junctures and not assume that the contractor will figure it out and do the right thing.

This article is intended only to provide general information regarding legal issues. It is not to be relied upon for legal advice. Contact your attorney for advise and guidance on general and specific legal issues.

Go Back