Forensic Engineers and Consultants

Archive: Commercial

Construction Techniques to Prevent Water Penetration at Windows

Windows, and their interface with the exterior walls, are an important part of a building’s envelope that resists the intrusion of water. Most builders take many precautions to protect a house from water damage. One of the most important factors in keeping the water out is the installation of window flashing, a thin material that prevents water from seeping in around a window. Over time, even a tiny gap around a window that allows water to enter can result in fungal growth, wood decay, and structural damage that can end up requiring costly repairs.

Expensive water leaks correlated with windows can often occur between the window units and their frames, but the most predominant leakage paths appear to be based on poor construction and installation techniques of the window and wall interfaces. Water infiltrating through these paths can cause considerable amounts of damage to the wooden framing which often is concealed until the water damage has become widespread. The water management components for windows include the following:

  • Sills and thresholds
  • Water-resistive barriers
  • Flashings
  • Caulking
  • Proper integration with the wall’s water-resistive system
  • Continuous drainage paths

The American Society for Testing and Materials (ASTM) Standard E2112, “Standard Practice for Installation of Exterior Windows, Doors & Skylights”, as well as the International Residential Code (IRC), provide guidance for the performance and construction requirements for exterior windows.  The International Code Council (ICC) provides direction.

“There are two key principles for effective flashing at windows and doors to allow water to drain down the face of the wall and away from the building:

  • Integrate flashing with the water-resistive barrier (WRB), e.g., house wrap.
  • Install membranes shingle-fashion where the top layer of the WRB or flashing laps over the bottom layer to prevent water draining behind the bottom layer”.

One often overlooked component of window installation is the slope of the windowsill. Windowsills that lack a positive slope away are common in the field and contribute greatly to potential water intrusion, particularly when sill pan flashing is omitted in the sub-sill portion of the wall below the window units. Windowsills that are nearly horizontal or, worse yet, slope back toward the interior of the building, create relatively large edges that can collect water and can expedite deterioration of sealants and lead to water intrusion.

A good construction practice is to have a pronounced slope that aids in prompt drainage of water, thus deflecting it away from susceptible sill interfaces. The Brick Industry Association recommends a slope of 15 degrees away from exterior windows for brick veneer applications. This can be achieved by proper planning with the brick mason and determining the height to the window opening.

Replacement Window Flashing

Image Credit: JLC Online, Replacement Window Flashing  https://www.jlconline.com

Another important tool to prevent water intrusion is the use of a water-resistive barrier (WRB). This is critical in the areas around the window opening, which creates interruptions in the drainage plane. Careful attention should be paid to the details for window openings during the design and installation of the water resistive elements around them to ensure proper water management in these areas. Vital points to remember for the installation of WRB is the preparation of the opening with house wrap, felt, or building paper, and the integration with the sill, jamb, and head flashings in order to maintain a continuous drainage plane. As such, there is prescriptive information in the ASTM E2112 document.

Image Credit: Brick Industry Association, Water Penetration Resistance-Design   https://www.gobrick.com

The sub-sill framing below the window opening is another area that is susceptible to water leaks. This typically occurs at the lower corners of the rough opening in the wall, usually where the coverage of the water resistive barrier is minimal. As such, the pan or sill flashing serves to protect the sub-sill framing of the wall and interior portions of a residence beneath the window openings that are susceptible to leakage. Consequently, the sub-sill drainage provided by pan or sill flashing is crucial in achieving the performance and longevity of installed windows. Lastly, the jamb and head flashings will provide reinforcement to prevent water intrusion.

So, you may ask, “How can I find water leaks in my residence without an invasive approach?”  A non-destructive method to identify water leaks in windows is by thermal imaging. Thermal imaging is an essential tool for detecting moisture intrusion. During an investigation, the infrared technology can quickly and non-invasively zero in on the area of concern to find anomalies that may be created by moisture cooling. Monitoring the weather is crucial for successful results. Consequently, it is imperative to choose the optimum time to test and maintain a proper temperature control.  For example, the greater the span in temperature from the outside to the inside of the residence, the better the thermal results. As such, a warm or hot climate is excellent for thermal inspections since air conditioning is cooling the interior of a residence.  The following image depicts an example of this technique.

As can be seen in the above image, the blue areas below the windowsill illustrate an example of a concealed water leak behind the gypsum wall board. It should be noted that the thermal images can reveal a growing problem that can lead to more extensive water damage to a residence.

This residence had substantial water leaks coming through the windows, consequently developing extensive wood decay around the perimeter of the window frame.  Due to the ability to remain undetected, hidden water leaks can grow to become large losses. Using non-destructive tools, such as the Fluke thermal imaging camera, the source of the leak can be identified without unnecessary destruction of property. Getting to the source of the problem as soon as possible is key to avoiding potentially extensive repair work.

Carlos Zarraga has more than 8 years of engineering experience in the structural field specializing in building design, building components and foundation design.  Carlos has designed and analyzed structures, supervised designers and drafters, prepared construction documents and provided on-site duties for field supervision and inspection of construction projects. Certified in RISA 3D, RISA Foundation and RISA Connection, he is well-versed in the analysis of foundation failures.   He often determines the root cause of failure and the resulting scope of damage.  He has designed retrofits to existing structures in addition to repairing construction defects.  He also has experience in the industrial and petrochemical industry designing structures for materials handling facilities and industrial buildings.  Carlos holds a Bachelor of Science in Civil Engineering from the University of New Orleans.

The CE Mark and What Should It Mean to You? Part One

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Two little letters, CE.   Perhaps you have seen those two letters on a machine nameplate or some other equipment.  What is the meaning behind those two stylized letters and how does it drive the design of safer machinery?   Let’s take a closer look. Read More

Hidden Heat: The Unseen Hazard of a High Resistance Connection

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A typical residence can have upwards of 10,000 feet of electrical conductors installed, most of which are buried in the walls, attics and crawlspaces.  A commercial building can have 100,000 to upwards of 1 million feet of electrical conductors.  At each device such as a switch or a receptacle are at least three, and typically six or more connections of these conductors within a junction box.  The connections can be in the form of twisted connectors, screw terminals, push in terminals and crimped connectors.

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Failure to Maintain Tow Hook Latch Results in Bystander Death

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An unfortunate and tragic case that we investigated involved a commercial “rollback” recovery truck that was being used to transport a four-wheel drive diesel pickup.  The diesel pickup was not in running order with its’ engine in the bed of the truck.  Consequently, a commercial towing company was hired by the truck owner to transport the truck.  In the process of loading the truck onto the rollback, the truck came uncoupled from the winch and cable system.  The truck then rolled down the inclined bed of the rollback, running over and killing a bystander. Read More

Why the Structural Load Path MUST be Considered During Renovation to Prevent Property Damage

Understanding the structural load path is imperative when considering renovations in a home that may require the removal of a load-bearing wall. Some homeowners consider adding a new door or window opening and worry if the structure will collapse. Another reason could be that the owner wants an open concept floor plan. The goal is to remove walls and open their living space. Read More

Water in the Light Fixtures??? How HVAC Defects Appear in Strange Places

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One of my more interesting calls and subsequent forensic investigations was regarding water accumulating inside of 2X4 fluorescent light fixtures in a suspended ceiling of a secondary school in South Carolina.

The client called and indicated that the metal chassis of the lights were sweating and generating enough water to accumulate on the diffuser lens of the lights.  Obviously, an on-site investigation was in order! Read More

When the Walls Come Tumbling Down… Retaining Wall Basics

A wall is really boring until it fails. A retaining wall is supposed to hold back soil to either support a structure or keep a space clear. When it fails, both of those roles are compromised. A retaining wall does not have to collapse to fail. In fact, a failure is perhaps better defined as when the wall does not perform as expected. Read More

Machine Guarding and Risk Assessment

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The Occupational Health and Safety Administration (OSHA) “Top 10 for 2018” violations once again have Machine Safeguarding earning a position on the list. Machine safeguarding was the 9th most cited standard as noted in the list below:

  1. Fall protection, construction (29 CFR 1926.501)
  2. Hazard communication standard, general industry (29 CFR 1910.1200)
  3. Scaffolding, general requirements, construction (29 CFR 1926.451)
  4. Respiratory protection, general industry (29 CFR 1910.134)
  5. Control of hazardous energy (lockout/tagout), general industry (29 CFR 1910.147)
  6. Ladders, construction (29 CFR 1926.1053)]
  7. Powered industrial trucks, general industry (29 CFR 1910.178)
  8. Fall Protection–Training Requirements (29 CFR 1926.503
  9. Machinery and Machine Guarding, general requirements (29 CFR 1910.212)
  10. Eye and Face Protection (29 CFR 1926.102)

(Source: www.osha.gov/Top_Ten_Standards.html)

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Unguarded Shear Point on Force Tester Amputates Worker’s Finger

A worker was injured while testing gas springs similar to the type that hold the hatchback of an SUV open. The hazard that injured the worker was an unguarded shear point. The tester contained a mounting plate that was raised and lowered by a pneumatic cylinder.

The pneumatic cylinder lowered the mounting plate while the worker’s fingers were in the hazardous, unguarded shear point. Read More

Hazards Can Lurk Anywhere … Watch Your Step …

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While on a lunch stop during a recent vacation trip through Tennessee, I happened across a safety hazard that required immediate attention.  The establishment had a raised concrete patio at the front with a steel railing around the perimeter.  At one edge of the patio was a set of stairs with a continuation of the steel railing used as a handrail.  The top edge of the patio had light strings wrapping the top metal bar as accent lighting for the perimeter.  The light string continued down the stair handrail wrapped in the same manner as the rest of the patio. Read More

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