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How Improper Building Waterproofing Leads to Building Envelope Failures


When moisture penetrates the building envelope during construction or occupancy, it can cause extensive damage. Many times, water penetration is due to faulty installation, improper construction, or the use of unsuitable materials.

Ultimately, the design team is responsible for having the expertise and knowledge to create construction design documents that reflect a properly waterproofed building. The construction team is responsible for professionally carrying out those designs.

To that end, construction design review services ensure construction documents are specific, clear, and technically sound before a job goes to bid. CTL Engineering’s building envelope consultants are called on to review and make suggestions on construction designs for a wide array of building infrastructures.

Solid design work ensures proper building waterproofing

Good design is a foundation of proper waterproofing and is critical to the health of a construction project. If the design is substandard, even the best installation and materials will not suffice. For example, penetrations in a foundation wall calls for first and foremost, a detailed design. Correct materials and installation must follow, but the design is the foundational part of any building project.

Improper materials and installation lead to faulty building envelopes

Aside from design problems, the most common errors made with building envelopes involve using the wrong materials or improper installation of them. Even a small, negligent leak can lead to extensive building damage.

Further, a construction material will not perform correctly if it is misused. Problems with materials may not reveal themselves immediately, but over the long term can lead to the failure of the building envelope and significant water damage.

Construction design documents must be detailed and adequately describe the materials for each job. Proper installation should follow based on the design. A contractor who cuts corners or skips steps on the construction process is only inviting structural, financial, and even legal problems for building owners.

Waterproofing problems we often encounter

As building envelope consultants and forensic engineering experts, CTL often encounters waterproofing problems when called for building envelope inspections. The most common waterproofing problems often involve roofing and windows.


Proper roofing is the most important defense against rainwater intrusion. Flat roofs, also known as low-slope roofs, should be designed with a ¼” per foot slope to discourage standing water. Flat roofs are the most common design for commercial construction projects.

Pitched roofs are designed to shed water but can be a problem if an ice dam develops due to improper design.

Another essential design feature for waterproofing roof systems is a proper underlayment material. An underlayment acts as an added layer of protection. Residential roofs may also be ventilated to remove moisture from roof cavity spaces and prevent condensation build up.

Material failures are common in roofing construction, so they need to be inspected and repaired regularly. If these routine maintenance steps are overlooked, simple repairs can turn into premature material failure. A typical commercial roof membrane can last 20 years. If it is designed, installed and maintained correctly, though, it can last 25-30 years.


Improper installation or the omission of flashing on windows is also a common problem. CTL often encounters poor waterproofing around window installation. For example, our team was recently asked to review a project because the contractor had reservations about the design.

CTL reviewed the design and found the window openings were not properly flashed and sealant was not applied because it wasn’t called for in the construction documents. CTL worked with the field superintendent to make the corrections before a costly mistake was made.

Internal condensation and HVAC systems

Accumulation of internal condensation is another common area in which CTL finds building waterproofing problems. Improperly designed HVAC systems can cause condensation buildup. Look for ceiling tiles that curl at the edges and corners, indicating the presence of moisture. Warped ceiling tiles are an indicator of ventilation problems and high levels of humidity. Condensation can also build if ductwork comes loose or insulation isn’t correctly attached to the ducts.

Another common cause of condensation buildup is problems related to the water vapor barrier. During a water damage inspection, engineers often find no water vapor barrier or one that was installed incorrectly.

Why companies turn to CTL for successful building envelope waterproofing

CTL Engineering’s building envelope consultants are experts at identifying design issues that can lead to waterproofing problems.

Our team has the extensive technical knowledge and construction expertise needed to review design documents. We provide feedback and suggestions to help avoid building envelop failure.

CTL has a track record of success. We work with companies, projects and building envelopes of all sizes to successfully consult on hundreds of projects. This breadth of work gives us the experience to identify and correct problems before they cause substantial damage. CTL also conducts building envelope forensic analysis if trouble has already begun.

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