By Ed Wrenn
February 6, 2014
There is a need for the design of exterior walls to incorporate the concept of reliability engineering and parallel systems to improve functionality of drainage systems for the lifetime of buildings. In membrane/drainage systems, the exterior building envelope contains the drainage wall system which consists of the cladding as the primary water barrier and a secondary drainage layer (weather-resistive barrier) within the wall. Examples of claddings utilizing membrane/drainage systems include stucco, drainable exterior insulation and finish systems, manufactured stone veneer, vinyl siding, and wood sidings. Typically, there are multiple systems to remove water/moisture from the exterior wall system, though this paper will only address liquid flow to the exterior. Currently, the exterior building envelope is usually designed and installed in a manner where failure of one drainage system allows water intrusion and cumulative water damage to building components. Design standards and reference materials do not address the need for redundant flashing and drainage component installation to account for any failure of a single element. If drainage elements were installed in parallel, then failure of one system would be mitigated as another element could then drain water to the exterior of the building and prevent damage.
Reliability engineering and parallel systems
Exterior wall systems should incorporate the concept of reliability engineering and utilization of parallel systems to ensure proper functionality of drainage systems. Reliability engineering of water management systems can significantly improve the chances of preventing failure of the drainage system(s), damages due to water intrusion, and allow the structure and its associated components to meet its expected lifetime. Water intrusion is water that penetrates beyond the weather-resistive barrier (WRB) of the wall in such a volume that it cannot be removed by the mechanical system. This water has the potential to cause deterioration of sheathing, framing, interior finishes, and furnishings . Buildings should be designed and constructed in such a manner that drainage components are configured in a redundant (or parallel) manner to increase reliability of water management systems.
Reliability is defined as the probability that an item will adequately perform its specified function for a specified period of time under certain environmental conditions . The reliability of a system of items is the probability that the system will remain functional and not fail. Reliability is often mistaken with quality. Whereas quality is a static metric, reliability incorporates performance over a period of time, which is much more applicable to building performance.
Water intrusion causes damage which reduces the lifetime of materials and can lead to costly repairs. Significant damages within walls can also remain hidden for long periods of time augmenting damages and potentially resulting in emergency repairs. Buildings must be designed and built to resist water intrusion for as long as the designed life of the building or cladding components, which is generally twenty (20) years or more. In order to meet this requirement, designing and installing parallel water drainage systems is a more reliable method because if one system fails or is improperly installed, another will continue to drain water from the wall system.
The reliability and probability of failure of the exterior wall envelope drainage systems is not specifically addressed by the current design guidelines and literature. Many standards are focused on limiting the precipitation that strikes exterior walls and then penetrates to the weather-resistive barrier. Though there is some guidance stating to use systems proven to drain effectively in the appropriate climate, very little of the design guidance mentions flashings or drainage systems in parallel to create redundancy. The only statement that promotes parallel drainage systems is from ASTM International’s E241-04 Standard Guide for Limiting Water-Induced Damage to Buildings, which states that the use of a combination of moisture control strategies is usually the most effective . There was some effort in the wake of exterior insulation and finish barrier systems failures to provide designs utilizing redundant drainage planes . Some of this guidance recommends multiple layers of WRB, but these layers are typically not all installed properly integrated with the flashing and drainage system and do not provide proper redundancy. Additionally, multiple layers of WRB would not be considered true redundant systems as they are the same material in a similar location experiencing equivalent conditions, thus each layer is not a system independent of the other layers.
The key benefit to a parallel system is that it will function if one (1) or more of its components function, whereas a series system will only function if all of its components are operational. From a reliability engineering standpoint, it is imperative to install drainage components as parallel systems so that a failure of one system would not result as a system failure causing water intrusion. It is important to note that installing flashings at every floor line of a multi-story building does not create components installed in parallel. Typically, flashings would be the same material from the same manufacturer, the same construction drawings would apply for each set, and they would be installed similarly. Due to these similarities, the failure of one set would make additional failures more likely. The components of a parallel system must behave independently. When a building is designed and constructed, parallel drainage systems will provide redundancy through incorporating components that behave independently, thus maximizing the probability of water being shed to the exterior thus providing long term protection to the building.
Current design and installation standards should incorporate the concepts of reliability engineering in order to provide buildings that meet or exceed their expected lifetimes. If one system fails, there should be a parallel component(s) to drain the resultant water and prevent damages to the structure. One example of a cladding system incorporating redundant design would be a pressure equalized rainscreen (“PER”) system. Simplistically, the PER is three (3) systems in parallel – the cladding / WRB / flashings, the capillary break formed with a cavity, and venting of the cavity removing moisture via air flow. The current mindset is that this type of system is a “high performance” cladding , whereas redundancy really should be an integral part of any structure. Redundancy will increase costs: however, there may be lower cost ways to implement redundancy and the project team should consider cost versus performance. Incorporating redundancy and the concept of parallel systems can help ensure buildings that perform properly and significantly decrease the chances of failure of the drainage system, even when design or installation errors have occurred.
List of References
 ASTM International, E2266-04 Standard Guide for Design and Construction of Low-Rise Frame Building Wall Systems to Resist Water Intrusion, 2004.
 Lawrence M. Leemis, Reliability – Probabilistic Models and Statistical Methods, Second Edition, 2009.
 ASTM International, E241-04 Standard Guide for Limiting Water-Induced Damage to Buildings, 2004.
 Charles W. Graham, Wall Design Redundancy for Improving the Moisture Performance of Building Cladding Systems in Hot-Humid Climates, Texas A&M University, 2000.
 David Altenhofen, Rainscreen and back-ventilated drained cavity wall systems: practical applications for high performance buildings.
November 11, 2013
In November 2013, an expert report created by Berman & Wright Architecture, Engineering & Planning LLC contributed to a recent $1.5 million settlement in a New Jersey construction litigation matter
Berman & Wright was retained by the homeowner of a newly constructed five-story (including basement) townhome located in Jersey City, New Jersey, to evaluate the location and proper limitations of the home in relation to current and historical flood zones
Berman & Wright’s services included research of historical building codes and FEMA flood maps, and the review of information provided by the City of Jersey City on the design and development of the community, to determine if the new townhome was properly constructed in a flood zone. Berman & Wright concluded that location of the townhome was within an “A” zone; an area designated by FEMA’s Flood Insurance Rate Maps (“FIRM”) to be a special flood hazard area. Jersey City Municipal Codes and the New Jersey State Building Code, at the time of planning and construction of the townhome, did not allow buildings with basements to be constructed below the design flood elevation assigned by the FIRM map; however, the basement floor of the townhome had been constructed approximately five (5) feet below the design flood elevation.
Berman & Wright’s expert opinion was clearly articulated in a cohesive report which included flood maps and supporting documentation.
Berman & Wright has provided consulting services regarding flood zone issues throughout the United States, including New Jersey, South Carolina, and Mississippi. Through Federal Emergency Management Agency (“FEMA”) training and continuing educational seminars, Berman & Wright’s employees are fully knowledgeable regarding flood zone design and construction in relation to local, state and national rules and regulations.
November 11, 2013
Montgomery County, PA – June 2013 marked the completion of construction on Berman & Wright’s first collaboration with Habitat for Humanity of Montgomery County, PA, the renovation of an existing 1890’s brick townhome.
Habitat for Humanity is a national non-denominational non-profit organization that empowers qualified, hardworking, low-income individuals and families to become owners of safe, simple, and affordable homes. Habitat for Humanity, through volunteer labor, donations, and individual grants, builds new or renovates existing structures for affordable housing. The prospective homeowners are required to volunteer on the construction of their homes and the homes of other Habitat families to obtain “sweat equity.” The volunteer labor and donated materials keeps the overall cost of the building to a minimum; and the value of the home is then transferred into a no-interest mortgage for the homeowner.
Located in the Historic District of Norristown, Pennsylvania, the condition of the townhome to be renovated was poor. Severe water damage through the original brick masonry walls deteriorated interior plaster surfaces and windows, a tree growing through the rubble foundation undermined the a two story bearing wall above, the integrity of many connections between the wooden floor joists and the masonry bearing walls was questionable, an added addition which housed a kitchen was deteriorating, and leaking roofs, were amongst many issues that needed immediate attention.
Habitat for Humanity has strict parameters regarding home square footages, numbers of bathrooms, and what appliances can be installed. According to Habitat International’s guidelines, only one bathroom could be constructed. However, a family of five was designated to purchase the home, a single working mother with three grown children and one toddler grandchild.
The original house had five bedrooms and one bathroom. Because only four bedrooms were necessary for the homeowner, the fifth (original) bedroom was utilized to expand the existing bathroom area. The new bathroom was then “compartmentalized” to include a separate toilet room, separate shower room, and a double vanity area; such that a maximum of four people could effectively use the bathroom at the same time.
HVAC soffits were designed around the perimeters of each bedroom, and the living and dining rooms, creating “tray” ceilings. This simple to construct, efficient way to circulate the HVAC ductwork and vents throughout the house created a “high-end” aesthetic to the interior of the house.
In addition, although Habitat for Humanity design parameters do no permit laundry rooms and dishwashers, a dedicated laundry area was incorporated into the re-design of the house, and plumbing for a washing machine and a dishwasher was “roughed in” for future use. Moisture mitigation materials were incorporated into the construction details, along with new insulation along all exterior walls. With new windows throughout, the energy efficiency of the home exceeded national standards by 50%.
Berman & Wright has continued to provide design and construction documents for Habitat for Humanity of Montgomery County. Construction documents for the renovation of another brick townhouse in Norristown have recently been submitted for permits, and the house is currently undergoing demolition of interior finishes.
Information regarding both projects can be viewed on Habitat for Humanity of Montgomery County’s website:
July 26, 2013
SOMERVILLE, N.J. – Berman & Wright welcomes Molly Izatt as the newest member of the New Jersey office. Joining the team as a Project Analyst, Molly is a recent graduate Wentworth Institute of Technology with a BS in Architecture and will be focused on the areas of Design, Forensic Architecture, and Building Diagnostics. Her background includes experience in the areas of architecture, drafting, carpentry, and construction, and her interests include historic architectural and adaptive reuse.
Molly is a great addition to our firm and we are pleased to welcome her to Berman & Wright.
July 16, 2013
Brief History and Membrane Types
Single ply membrane roofing was first introduced in the early 1960’s as an economical means to protect and water-proof low slope roofing without the cost and labor intensive heating methods associated with traditional asphalt and coal tar pitch roofing. Single ply roofing can be secured to substrates through mechanical fastening, adhesives (full adherence), and /or ballasted with gravel, pavers, etc. these roof membranes consist of three basic types of materials: EPDM (ethylene propylene diene monomer “rubber”), TPO (Thermoplastic Polyolefin), and PVC (polyvinyl chloride “plastic”). EPDM, the first to be introduced to the market, is a vulcanized or cured rubber product and is often referred to as a thermoset. EPDM sheets are produced in a variety of thickness from 30 to 90 mils and can also be produced in a variety of colors with the most common being black. EPDM roofs are typically adhesively applied and seamed, and are often ballasted
TPO roofing membranes were introduced to the construction industry in the early 1990’s and like EPDM, TPO membranes can be either mechanically fastened or fully adhered to a substrate. However, unlike EPDM, and TPO can never be applied as a ballasted system due to the chemical composition of the membrane. During installation, the seams of TPO sheets are hot-air welded as opposed to glued or taped. TPO membranes are produced in thicknesses ranging from 45 to 90 mils and have become a popular choice in recent years as they can be more energy efficient due to the reflective nature and associated energy efficiency of white membranes. PVC membranes are also heat welded single ply membranes, and are typically produced as a white sheet similar to TPO’s. PVC offers several unique advantages when compared to other membrane types including durability, pliability, and recyclability. The chlorine in PVC membranes also offers superior chemical and fire resistance.
Design and Warranty Considerations
The first aspect of the overall single ply roof design to consider when selecting a membrane type is buildings height, geographic location, and wind exposure. The International Building Code mandates that the roof be designed to withstand wind uplift pressures based upon the published wind speed maps, and ASCE (American Society of Civil Engineers) 7 calculations. Many architects utilize Factory Mutual (FM) classifications as a means to establish a standard of quality and the design wind uplift pressure whether the building is truly FM insured or not. While this is generally an accepted practice, it is important to understand that these specified wind uplift pressures do not correlate to the roofing systems warranty, and that any desired wind speed warranty must be addressed separately. When selecting the appropriate membrane type for the building, the thickness of the membrane must also be selected, as thicker membranes offer significant increases in puncture resistance, thickness over scrim, weather ability, and seam strength, usually for a minimal increase in cost.
The substrate materials to be installed below the single ply membrane must also be carefully considered. The overall integrity of the single ply membrane is only as good as that of materials installed below it. Extruded polystyrene (XPS) or expanded polystyrene (EPS) insulation boards have a long history of use under single ply roofing membranes. In most cases these products can be fully adhered or mechanically fastened, and in some cases can be loose laid and ballasted over the single ply membrane. Polyisocyanurate insulation is also a popular choice for roof insulation material for low slope and flat roofs. Polyisocyanurate insulation offers several distinct advantages over XPS and EPS as it is more durable, dimensionally stable, and offers a higher “R” value per inch than that of XPS or EPS. Polyisocyanurate insulation is approximately 6.0 R value per inch of thickness and therefore allows the architect or designer to more easily achieve the insulation requirements mandated by today’s stringent energy codes, as well as ASHRAE (American Society of Heating, Refrigeration, and Air Conditioning Engineers) 90.1. Polyisocyanurate insulation is also produced with a more durable coated fiberglass face on each side in place of the standard black paper facer, offering superior fire resistance, higher wind uplift performance, and greater mold and mildew resistance. Whichever insulation board is ultimately selected for the project, it is important that the total thickness needed be comprised of at least two layers of the insulation material, such that the joints between the boards can be staggered, and reduce the possibility of thermal bridging.
The edge or perimeter condition where the roof membrane terminates at the parapet or wall must also be part of the overall system design. All single ply roofing manufacturer’s produce a variety of copings, gravel stops and other metal edge products to address most roof conditions. In fact, all single ply roofing manufacturers require the use of their proprietary edge systems to uphold their specified warranty. More importantly, the use of manufactured edge metal is actually codified in Chapter 15 of the International Building Code. Section 1504.5 Edge Securement for low-slope roofs states that “low-slope membrane roof system metal edge securement, except gutters, shall be designed and installed for wind loads in accordance with Chapter 16 and tested for resistance in accordance with ANSI/SPRI ES-1 test.” Without this knowledge, many contractors substitute the factory manufactured edge metal for coping or gravel stops that are fabricated in a local shop. This decision, often made in the interest of time or cost savings, ultimately compromises the roof warranty and doesn’t meet the building code requirements.
Lastly, the warranty for the overall roofing system must also be carefully considered. Simply selecting whether the building owner would prefer a 20 or 30 year warranty falls short of truly understanding what needs to be specified. Warranties are often a source of confusion among architects and building owners. For example, an assumption that the roofing system was designed to withstand wind uplift pressures of a 90 mph wind and specifies FM Global standards improperly implies that the warranty must also be for up to a 90 mph wind. However, the industry standard for wind speed warranties is 55 mph, unless otherwise specified as a specific requirement of wind speed to be provided by the manufacturer. Most single ply roofing manufacturers do offer higher wind speed warranties; however, the granting of such a warranty is dependent upon the overall system design and other components utilized in the design. Too often the designers, contractors, and building owner come to this realization during the roof installation, when it is simply too late to address the issue without significant cost increase and time delay.
Single ply roofing membranes are often an appropriate choice for a variety of building types and can serve a building for many years. They are often unique to each manufacturer and the design and wanted warranties can be complicated. Architects, Designers, Contractors and Owners must understand all aspects of the specified system in order to avoid a myriad of issues that can arise both during construction and throughout the life of the building.
July 8, 2013
SOMERVILLE, N.J. – Berman & Wright welcomes Andrew Illein as the newest member of the New Jersey office. Joining the team as a Project Analyst, Andrew is a recent graduate of Syracuse University School of Architecture and will be focused on the areas of Design, Forensic Architecture, and Building Diagnostics.
Andrew is a great addition to our firm and we are pleased to welcome him to Berman & Wright.
April 16, 2013
Somerville, N.J. – Berman & Wright Architecture, Engineering & Planning, LLC is pleased to announce the promotion of Rob Klein, CPE to Senior Project Consultant.
Rob joined the firm in 2006 as a Project Consultant in the Somerville, N.J. office. Rob is a licensed Building Sub Code Official and Construction Official in the State of New Jersey, and recently earned his qualifications as a Certified Professional Estimator (CPE), through the American Society of Professional Estimators.
As a Senior Project Consultant with Berman & Wright, Rob will be involved in the supervision and management of all phases of projects and work product development.
We appreciate the expertise and dedication that Rob brings to Berman & Wright. His commitment to excellence continues to support the firm’s position as a leader in the design, construction, and diagnostics industry. Please join us in congratulating Rob on his accomplishment and new position at Berman & Wright.
March 26, 2013
Berman & Wright is proud to acknowledge the accomplishment of Rob Klein who recently passed his professional examinations to achieve the recognition of Certified Professional Estimator (CPE), ASPE Certification, through the American Society of Professional Estimators.
Through its Certification Program, the American Society of Professional Estimators recognizes the proficiency and ethical awareness of the Certified Professional Estimator. This certification is obtained after going through an educational process, submission of an acceptable technical paper, and successful completion of written examinations. Rob was a candidate for certification since mid-2012, and recently completed the requirements, proving his ability and practical experience in the profession.
As a Project Consultant for Berman & Wright, Rob is responsible for planning, project management, and performance of on-site building diagnostic investigations and specialized testing. Additionally, Rob provides detailed construction estimating services which is now further enhanced by his achievement in being recognized as a Certified Professional Estimator.
Berman & Wright commends our employees for their hard work and dedication and for helping to maintain our competitive edge. The insight, expertise, and knowledge we share with our clients sets us apart as a recognized leader in the construction industry. We proudly congratulate Rob on his accomplishment.
March 15, 2013
Berman & Wright Architecture, Engineering & Planning, LLC is proud to announce the promotion of Katie Wright to the position of Marketing Manager.
Katie has a degree in Communication Studies with an emphasis in Public Relations and a minor in Journalism from the University of North Carolina – Charlotte. With her hands-on experience in the field of public relations, Katie is instrumental in channeling this expertise towards the advancement and growth of the firm. In her new role, Katie will plan and execute all marketing efforts for Berman & Wright from our Cornelius, NC office.
Berman & Wright values our employees and their passion for their work and client success. Please join us in congratulating Katie on her new position.
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March 12, 2013
Chinese Drywall cases have been on the rise in recent years, and Berman & Wright Architecture, Engineering & Planning, LLC (“Berman & Wright”) has been at the forefront of this issue, investigating conditions of the affected homes throughout the United States.
During the housing boom in the early 2000’s, and the subsequent years when a significant number of Hurricanes hit the Gulf Coast states, construction materials were in high demand. Drywall companies in the United States were not able to keep up with the demand for material production, and various companies turned to China to manufacture and ship materials to the United States. This included drywall used in new home construction and existing homes being renovated due to damages from Hurricanes and other storms. This defective drywall was mainly used in the regions of the East and Gulf Coasts; however, Chinese drywall was found to be used in at least 42 states across the United States.
Chinese drywall contains elevated levels of sulfur that is emitted into the environment, creating gases that can not only cause foul odors, but can also cause corrosion that affects wiring, electronics, piping, HVAC units, and appliances; and may lead to electronic failures and risks of fire.
Rigorous testing and investigations were performed in the field and in laboratories, verifying the relationship between the use of Chinese Drywall and the extent of the associated damages within homes where the drywall was used.
Federal Court rulings recommended that contaminated homes be completely gutted for remediation and recently approved a number of pending settlements for parties included in the distribution and sale of the Chinese Drywall. These settlements are intended to provide proper funding for homeowners to perform remediation to their impacted homes.
Berman & Wright provided services for many cases involved with the recent settlement. These services included investigations and documentation of conditions within homes, analyses of scientific results from testing of building components taken from homes, and development of the remediation scope of work necessary to address the conditions within the homes.