Building envelope professionals generally follow two evaluation techniques to assess a building's exterior condition and develop a Scope of Repair.

The most common method, forensic investigation, is intended to provide a 'blind simple random sampling' (SRS) or quantitative sampling which involves the collection of a sizeable amount of data to develop a statistically relevant sampling. The large number of intrusive openings required for this process make it a lengthy procedure and disruptive to occupants. It is logistically challenging, cost prohibitive and results in numerous unsightly 'patches' that must remain until a Scope of Repair can be carried out.

Moreover, because the majority of water intrusion through the envelope occurs at material transitions and changes-in-plane, random selection of sample locations is not an effective investigative approach as these design elements do not occur consistently throughout the building enclosure. For these reasons, this approach is widely considered to be impractical, inefficient and a potentially ineffective method of conducting building envelope evaluations.

Alternatively, the standard protocol put forth in ASTM E 2128 (Standard Guide for Evaluating Water Leakage of Building Walls) dictates a process of conducting targeted evaluations of building components consistent with the principles of qualitative sampling.

The procedure for this Standard starts with information gathering, includes a field investigation which builds on each invasive opening, and has flexibility built in to the process to allow for a change of course depending on the field information that is gathered. Observations can be supported by field and laboratory testing, as needed. Before beginning the field process, information gathering should identify "performance expectations and service history of a wall, the various components of a wall, and the interaction between these components and adjacent construction"(1). Ideally, the evaluation team will have had the opportunity to review project records, building history and design concepts prior to the commencement of field work. Once field work begins, the course of its progress is determined by the findings at each opening. This requires regular attendance and constant attention from the lead evaluator throughout the field data gathering process. In short, an investigation cannot be run by an absentee lead evaluator.

Section 11 of the Standard details a summary of the protocol for a qualitative investigation:

  • "11.1 ...An evaluation is conducted in response to a problem situation and a non-performing wall, and may involve several techniques and procedures specifically adapted and applied in a systematic manner to diagnose a specific problem." This differentiates this Standard from a 'Building Assessment' as detailed in ASTM E 2018(2).
  • "11.2 The information systematically accumulated in a leakage evaluation is analyzed as it is acquired. The new information may motivate a change in approach or focus for subsequent steps in the evaluation process."
  • "11.3 The evaluator is expected to establish a cause and effect relationship between wall characteristics and observed leakage. This requires an appropriate selection of activities and a logical analysis and interpretation of the acquired information..."
  • "11.4 The conclusions and findings from an evaluator must be rationally based on the activities and procedures undertaken and the information acquired, if they are to be considered legitimate and substantiated."
  • "11.5 The record should be sufficiently complete so that any interested party can duplicate the evaluation program and acquire similar information. Notes on the analysis and interpretations of the acquired information should be clear and complete enough to be understood by any other building professional skilled in leakage evaluation."

The Standard outlines a qualitative approach to identifying the cause and effect relationship between building envelope characteristics (design elements), 'as-built' conditions, leakage and the resulting damage. Clear and concise recordkeeping of the investigation is a requirement of the Standard. It also requires that another qualified professional be able to duplicate the investigation and findings.

ASTM E 2128 also promotes the process of qualitative testing to advance the investigation. It recognizes that such testing is "an integral part of the evaluation process, and should be thought of as a means to verify and extend hypotheses arrived at during the document review and inspection phases of the program using controlled and reproducible procedures"(3). The Standard promotes the concept of supplementation of qualitative testing with quantitative testing of material properties. It also notes that "some leakage problems can be diagnosed and corrected with little or no testing".

ASTM E 2128 Investigation Sequence

A critical component of ASTM E 2128 is the provision of a systematic approach and sequencing of both research and field activities. It is intended to provide an organized and efficient method for accumulating information where each step supplements and advances the information gathered in the preceding step.

The Standard provides for the following steps:

1) Review of Project Documents: The first step is to carry out a thorough review of the original project documents. The evaluator will gain an understanding of the materials used in the original construction and the Codes in place when the project was built. If the building was the subject of a prior remediation, the process should be clear in the permit file with the local authority, or the 'as-builts'. The document review should include design, bidding and construction documents, referenced codes and standards, submittals, and project notes.

2) Evaluation of Design Concept: The building evaluator must identify and evaluate the exterior wall design concept to make certain that the initial performance standards are being met. For example, if the design of the exterior wall is a barrier system(4), the exterior wall must be completely face sealed to resist 100% of the water that hits it. All components making up the wall assembly must work in harmony to resist any moisture entry.

The design concept review must include evaluating the potential for water entry from both the interior as well as the exterior, which may require computer modeling of exterior walls. The analysis of the design concept should consist of a review of the materials that make up the total wall assembly, potential service life and any potential compatibility issues identified either in the original design or in the as-built conditions. Where redundant systems have been installed, the intended service life of each component must be assessed. The evaluator must have a thorough comprehension of the materials that make up the wall assembly; how they perform as an assembly, and what the expected service life of each material should be based on the original design.

3) Determination of Service History: The service history can be defined as the maintenance and remediation records which identify where water has entered in the past and what type of repairs have been carried out to correct the conditions. By mapping prior repairs and remediation, project patterns can be identified including accelerated weathering on elevations impacted by prevailing weather patterns, shaded areas from adjacent buildings or vegetation, or south elevations that experience great daytime heat gain. Determining a building's service history may require both visual site inspections and site interviews to aide the evaluator in establishing a better picture of the overall performance of both the original materials utilized and those put into service post-construction. All physical symptoms of leaks or wall distress should be documented during the visual inspection. Special attention should be given to wall intersections, material transitions, handrail connections, and penetrations. A careful review will make evident exterior signs of distress, surface condensation, corrosion and breaches in the envelope, information that will help in the development of the Scope of Investigation.

4) Field Inspection: The data gathered from the document review and the visual observations forms the basis of the investigation. Water paths are identified and traced to their source, while the varying levels of damage are assessed. Weather patterns, drying capabilities and quantities of water that may have entered at each point are assessed. The evaluator must formulate an initial hypothesis regarding the cause of water leakage at each opening, carefully document inspection findings, and use the collected data to move to the next point of investigation. Conducting inspections according to a well-reasoned and organized investigation plan will provide the most useful results. Rational selection of inspection locations based on the initial research and site observations, as well as proper documentation of investigation findings, is essential. Depending on the type and sequence of gathered data, additional visits to the site might be necessary to confirm or expand collected information.

5) Investigative Testing: Field testing should be an integral part of the evaluation process. Test results can be used to confirm or support hypotheses developed during the investigation. Though some leakage problems require minimal, if any, field testing, additional testing data can help diagnose the extent of the condition and assist in developing an appropriate correction. Field tests can also help the evaluator recreate leaks, trace the internal path of a leak, correlate test results with observed damage or verify a previously developed hypothesis. Testing should be well-planned and should result in the identification of water entry points. As an example, a moisture meter that is properly calibrated and is equipped with the appropriate probes can quantify the extent of moisture accumulation and help determine whether there is sufficient moisture to promote organic growth. The testing should generate more than a fail/fail result; it should assist in the quantification of the condition and in the development of the Scope of Repair.

6) Analysis: The analysis of collected field data on an ongoing basis is an essential component of a qualitative evaluation. Analyzing data as it is collected allows the evaluator to change approach or investigation focus depending on findings generated during field work. The goal of the analysis is to establish a cause and effect link between wall characteristics and observed leakage. To accomplish this, the analysis must focus on issues such as:

  • Reduction of quantitative data
  • Resolution of conflicting data
  • Identification of data patterns and commonalities
  • Identification and explanation of anomalies
  • Correlation with known wall performance
  • Corroboration between various procedures used during the investigation

The record of the analysis and related data should be complete enough to allow a third-party to duplicate the evaluation program and acquire similar information. In short, the analysis must be carried out on an on-going basis during the investigation process and will likely change the course of the investigation more than once as the evaluation progresses. A rigid Scope of Investigation will miss important data unless the number of openings is greatly expanded, catching the conditions in a shotgun spray of openings throughout the exterior.

7) Report Preparation: The last step in the process is the development of a report describing the process of initial data collection and site observations, the methodology utilized, the data collected, and the findings and conclusions. This report should be comprehensive in nature as it will become part of the permanent project record for the building being evaluated. Data can be formatted in a wide variety of ways to convey the process, findings and conclusions to meet the needs of a specific audience. However, a formal itemized report covering all relevant issues should be generated for safekeeping with the other project records so future evaluators will have the benefit of the information resulting from the investigation process.

ASTM E 2128 presents a clear and concise protocol for the evaluation of buildings that have known or suspected water leakage. The qualitative approach to data collection and field evaluation creates a logical, comprehensive and cost-effective methodology for conducting a building envelope investigation. The process is comparable to validated practices of qualitative analysis used extensively in the social science fields and is widely accepted as an appropriate and effective method for conducting building envelope evaluations.

December 2008
Issue Three, Volume Three



This article by Colin Murphy.

Colin Murphy is the founder and managing partner of Trinity | ERD.

Trinity | ERD
http://www.trinityerd.com

ASTM International Standards Worldwide

 


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