By: Mike Stellato, AIA, LEED AP, CSI, NCARB Certified, Principal - Star Consulting Group
What is now considered “common knowledge” is most often learned from mistakes of the past. For example, it is now considered standard practice of the industry to have an air barrier around all six sides of a building envelope. Not too long ago this was
Sometimes buildings do not perform to the purpose for which they are designed. This can be a matter of function with the design of spaces and also the design of the building envelope. In the case of a building envelope, many factors can and do influence the design and construction of the building skeletal shell and exterior skin. Such factors may include budget, value engineering, construction method, time constraints, season, location and environmental influences. These factors may influence the actual materials used and the methods of installation. Sometimes evidence of failure occurs before completion of the project; sometimes many years later. However, in all cases where building envelopes fail, the results are damage to the building and dissatisfaction of the user. With building envelopes, it can be water leaks, moisture laden cold walls, high utility bills and inefficient HVAC functions related to the failure of insulation in roofs or walls.
Such was the case of a 15-year-old high profile municipal building with multiple failures of the roof and exterior skin. Investigation and destructive testing proved that there was massive failure of the roof surfaces with wet insulation caused by roof coping a
A number of investigative techniques were used to assess the condition of the envelope condition including thermography, moisture meters and destructive testing. Destructive testing showed no flashing whatsoever was used anywhere in the building. Not even the sheathing joints were sealed. The EIFS was the only waterproofing! Gaps of two to four inches around the rough openings of windows were common. In most cases the back side of the interior gypsum board could be seen from the exterior. At the areas of stud framing where gypsum sheathing was used on the sills, water leaks had dissolved the gypsum, rusted the studs and plates and infiltrated into the insulation. EIFS was also used at the copings. Maintenance crews did not use the davits and outriggers provided, but hung by ropes over the sides creating massive failure of the EIFS coping edge surfaces, and thus creating entry for water into t
One would think this was a ‘slam dunk’ investigation case with an obvious outcome, but this was a very geometrically complicated building with over 450,000 square feet of EIFS exterior wall surface. After much deliberation of the extensive damage and repairs needed and estimation of costs for repair, it was determined that the only course of action for the environmental security of the building was a complete re-skin of EIFS over a new waterproofing barrier and flashing around the windows and on the sheathing. A new roof system was also called for. Research on the existing building was extensive to insure proper detailing of all conditions that would be encountered.
Coordination of system interfacings, flashings and materials was imperative to ensure air and moisture tightness of the exterior envelope. Construction documents were extensive to outline not only the repairs, but the demolition. Dimensional accuracy was imperative or the building’s geometric parts would not align together properl
A new roof membrane using an SBS system over tapered insulation was selected on the zero-slope structure because of existing features and flashing points. This also accommodated plaza deck paver areas best without the need for pedestals. Integrating counter flashing in with the EIFS system was critical. Wall to roof metal flashing was installed prior to the EIFS repair and the new drainage plane system. New compressible roof drains were installed that prevented water from entering the new roof insulation layers. Because of past maintenance issues, some of the coping areas were converted from EIFS to colored metal coping with special detailing to eliminate a shadow line.
Wall surfaces took much more planning and detailing. Replacement of the EIFS was sequenced on the building from top to bottom. Once the existing EIFS was removed, the portions of the building that were concrete were smoothed out an
The most difficult part of the wall detailing was the areas around the windows. End dams in the window framing system had totally failed. Water intrusion was so frequent that calcium had built up in the sill framing. For cost and security reasons, the windows were kept in place during this entire process. To close up the huge gaps between the rough opening and the window frames, urethane foam was used to seal the space in the head, jamb and sills of all windows. This filled the open frame members and the oversized RO space and prevented most of the air infiltration from being a problem. Rather than replacing the age
Application of the new EIFS exterior wall system was done with a drainage plane system this time. Moisture intrusion into the wall surface can now be mitigated in several ways. First are the acrylic coating and silicone sealants used on the exterior as a first line of defense. Second is the drainage plane system designed to extrude moisture from the wall system with metal flashings above the window openings imbedded behind the EIFS, and thirdly, the waterproof coatings used on the substrate and flashings used around each window’s rough opening will protect the substrate from future damage and keep water from entering around the windows. It is important to note that the manufacturers of the systems used were a critical part of the design process. Mock-u
The important lessons learned on this project are that proper detailing is critical for the integrity of the building envelope and that no ‘value engineering’ (or ‘de-value engineering’) should be accepted that would reduce the effectiveness or integrity of the envelope system. Also, that no matter how bad a building’s envelope may be performing, it is feasible to rectify the situation; however, it may not be financially practical. All of this gives credence to doing things right the first time!
Mike Stellato is a Registered Architect and Principal of Star Consulting Group, having designed High-Rise buildings, Commercial, Industrial, Hospitality, Municipal, K-16 and most every other type of project using most all construction materials & methods of construction for more than 35 years. Associated with Forensic Building Analysis for over 12 years, Mike has provided design assistance and specification development, architectural review and analysis of product applications; contract administration, field inspections and testing; forensic investigation and analysis; and associated services related to new or existing installations of commercial glazing systems (glass curtain walls, skylights, window and doors), Exterior Insulation and Finish Systems (EIFS) and other exterior wall cladding systems, air barrier design, as well as all aspects of waterproofing and related products for walls, roof and foundations.
Mike can be reached at mjstellato@gmail.com or phone 210.887.7469