Forensic Engineers and Consultants

Archive: Structural

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.

Structure Fires in Eating and Drinking Establishments

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Eating and drinking establishments see an average of 7,410 structure fires per year based on a 2017 report published by the National Fire Protection Association (NFPA). The report analyzed available data from the U.S. Fire Administration’s National Fire Incident Reporting System (NFIRS) and the NFPA’s annual fire department survey for the years 2010-2014.

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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

Product Design is Critical to Consumer Safety

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As the holiday season nears, thoughts turn to wonderful home-cooked meals with family.  Few things in life are more pleasurable than a traditional holiday turkey feast. Yet for an unfortunate few, holiday meal time can turn tragic if a turkey frying accident occurs.   While fried turkeys may be tasty, many fire safety experts feel that the reward is not worth the risk.  Read More

Testing As Part of Gas Appliance Incident Investigation

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Equipment and appliances supplied with fuel gases like natural gas, propane and butane are a common and convenient part of most of our lives.  Such devices as gas grills and ranges, ovens, furnaces, space heaters and water heaters usually perform without incident.  However, when they malfunction the potential for incidents such as fires and explosions, carbon monoxide (CO) poisoning and burn injuries may occur. These incidents may be due to design and manufacturing defects in the product, or improper installation or operation of the device.

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Improper Fireplace Construction: Testing the Impact of Non-Compliant Clearance to Combustibles

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As the weather turns cold, many people use fireplaces to provide supplemental heat. The warmth from a fireplace is a comfort and the aesthetics of a glowing fire are a pleasure.  However, there is nothing pleasurable about a residential house fire that results from an improperly built or used fireplace or chimney. Read More

Post-Fire Inspection of Steel, Concrete, Masonry and Wood – Tips for an Insurance Adjuster, Part 2

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This is the second part of a 3-Part series to help insurance adjusters during a claim inspection to make a post-fire assessment of a building’s structural framing system.  Part 2 investigates and assesses the future use of common post fire structural framing elements such as steel, concrete, masonry and wood.  These more common structural elements take on different and specific characteristics when they are exposed to a fire.  It’s important for the adjuster to make reasonable, cost saving assessments on what remains, what is to be repaired, what gets demolished and what gets replaced. Read More

Structural Evaluation After a Fire – Post-Fire Tips for an Insurance Adjuster, Part I

Author

This is a 3-Part series to help insurance adjusters during a claim inspection make a post-fire assessment of a building’s structural framing system.  From my numerous case history inspections involving damage to structural framing members after a fire, what appears obvious and straightforward is not always the case.  This article is a quick synopsis to help the adjuster be better prepared for a structural inspection and assessment while understanding what needs to be looked at, and if there are hidden factors to further investigate. Read More

Fire Losses Involving Improper Construction and Installation of Fireplaces and Chimneys

Author

On a cold winters night a family is gathered in the living room of their home enjoying the warmth of their fireplace.  After using the fireplace all day, they go off to bed to a nice restful sleep.  However, they are soon rudely waked by the sound of a smoke alarm in the home.  Rushing out into the cold night they can see smoke, but no flame in the home.  Outside, they can see that the chase around the fireplace chimney is burning.  The fire department is called and thankfully extinguishes the fire before it does widespread damage, however the family must leave the home for several months as repairs are made. Read More

Explosion Investigations Uncover Answers

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The cause of an explosion can result from a chain of events in some cases. In many residential explosions and resulting fires, the facts can point to a number of potential causes. Certified fire and explosion investigators, like Warren engineers and technicians, have the experience and training to uncover and evaluate scenarios with high degrees of certainty. In some cases, like one residential explosion I investigated, the chain of events can start days before the loss.
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