Quality Checks for Building Façade

By August 23 , 2015
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Introduction

The word Quality is overused to an extent that it has become a cliché. Most of what we see around us is claimed to be of ‘good’ quality or of ‘high’ standards. This article relates the author’s perspective on how quality can be defined in Building & Construction focusing on Façade & Fenestration Elements.

It primarily focuses on three levels where “Quality Checks” are critical. These are explained by examples of curtain wall systems, building hardware and partition systems. Below are three levels of quality check:-

  1. Product Design
  2. Product Manufacturing
  3. System Design and Execution

It is important for key stakeholders (developers and owners, designers & architects, contractors and manufacturers) involved in creating buildings to be aware of these levels of quality as these will help them pinpoint possible aberrations. Compliance to certain or limited standards may give a false feeling of quality compliance to manufacturers or users.

Any product or a system which will be part of a building (glazing, hinges, window) has to perform throughout the claimed life of the building and should be in a position to endure known (High winds, rain) and limited unforeseen environments (like earthquakes, fire etc.) To develop and supply a product or a system that displays consistency/ repeatability of compliance evokes a satisfaction of quality. Various tools that are used by organizations to achieve these levels of assurance are discussed below.

QUALITY CHECK FOR PRODUCT DESIGN

It is common for companies to claim that their products comply with a certain standard and hence implying that these are a quality product. It is critical to understand the extent and boundaries of these standards.

There are a large number of standards (AAMA, ASTM, BS, CWCT, EN, etc.) for products. A standard can define either or all of the following:

  • test method
  • classification
  • practice
  • guideline

Fire rated curtain wall as per EN 1364-3

EN 1364-3 is a European Standard which specifies a test method for determining the fire resistance of curtain walling (full configuration)for non-loadbearing elements. The scope also defines that this European Standard does not cover double skin façades, over-cladding systems and ventilated facade systems on external walls. It does not deal with the behavior of curtain wall in case of fire.

TestMethod to check the compliance of a Fire Rated Curtain Wall with EN 1364-3

Such a test is conducted to verify the fire rating (in hours/minutes) that a particular design can endure. The standard details on the following:

  1. How to create the testing environment
  2. How to install the samples
  3. How and which all parameters are to be recorded during the test duration.

Below is a brief list of the steps for the above test:

Step 1. The sample is received along with detailed drawings of the system.

Step 2. Before and during the Installation, evidence is gathered to correlate the sample submitted with the drawings.

Step 3. Samples are carefully installed on to a frame representing the standard conditions.

Step 4. The system is loaded with thermocouples and sensors which will help capture change in temperature and other parameters to be recorded.

Step 5. The furnace is fired up. It is designed to simulate the increase in temperature and pressure as it would progress in case of a real fire

Step 6. The test sample is carefully monitored throughout the duration of the test for various parameters like changes in deflection of structure, rate of change of temperature, behavior of material, release of gases etc.

Step 7. The test ends in confirming the fire rating of the Curtain Wall system in minutestill which the system couldwithstand a real fire. (example 120 minutes of fire rating)

Step 8. A test report is compiled and issued capturing behavior of the system during the test as per the test standard.

This is a product level quality check and is the starting point to prove compliance of future performance of the product or systems in given environment. Testing with many combinations of systems, materials and environments may be necessary before the design can be claimed to perform as per desired expectations in unique environments.

Precautions to be taken while testing /choosing a test lab:

  1. Ensure the testing laboratory is accredited to ISO 17025
  2. ISO/IEC 17025:2005 specifies the general requirements that determine a lab’s competence to carry out tests and/or calibrations, including sampling. It covers testing and calibrations using standard methods, non-standard methods and laboratory-developed methods
  3. Accreditation is a process in which certification of competency, authority, or credibility is presented. Organizations that issue credentials or certify third parties against official standards are themselves formally accredited by accreditation bodies (such as UKAS- United Kingdom Accreditation Service)
  4. National Accreditation Board for Testing and Calibration Laboratories (NABL) which is India’s national accreditation body is a signatory to Mutual Recognition Arrangement with International Laboratory Accreditation Cooperation (ILAC)
  5. The International Laboratory Accreditation Cooperation – is an international cooperation of laboratory and inspection accreditation bodies formed more than 30 years ago to help remove technical barriers to trade. 36 laboratory accreditation bodiesfrom 28 economies worldwide signed an arrangement to accept each other’s Accreditation. This helps bring the test reports issued by laboratories accredited by different accreditation bodies at par (Example the report issued from a lab in India accredited to a standard by NABL is equal to the report issued by a lab in UK accredited to the ‘same standard’ by UKAS and vice-versa)
  6. The compliance testing should use a test standard which guides to simulate the conditions of the environment where the product will be finally used. For example ANSI (American National Standards Institute) is the body that adopts standards from various standard writing bodies like UL, ASTM, AAMA, etc. to declare them as the standards that are representative of the conditions prevailing in USA. Like the ANSI standards for fire resistance testing (for doors ANSI/UL 10C) makes it mandatory to conduct a Hose Stream test at the end of the fire rating testing. This is done to simulate the practice that is followed in United States where the fire department believes it is mandatory that the Fire Rated partitioning system maintains their integrity when the fire is extinguished.

QUALITY CHECK OF “PRODUCT MANUFACTURING”

Mass producing a tested and complied design requires that the exact same steps be undertaken to assemble/ make the system/ subsystems with the exact same components/ materials.

The selection of raw material and the design of the product is dictated by the end application. This could vary vastly for the same product.

Using the nomenclature of BS EN 1935, I would to bring out the extent to which the applications of a simple “Hinge” can very. The European Standard written by BSI is a standard for Single-axis hinges defining its requirements and test methods.

Below is an image explaining the 8 digits used to classify a single axis hinge

This standard helps create a test report to show compliance of the hinge design to the exact 8 digit code using defined testing methodology. Consultants designing systems use these classifications to specify hinges for their final system and need proof of continued compliance to these parameters.

Product Certification for assurance of performance repeatability:

One of the most commonly used system to create evidence of future performance of products or systems manufactured or assembled is Third Party Product Certification.

Independent agencies which offer product certification services need accreditation as per ISO/IEC 17065 from an accreditation body. ISO/IEC 17065is a standard defined as: – Conformity assessment — Requirements for bodies certifying products, processes and services (replaces EN 45011 and ISO Guide 65)

An accreditation to this standard empowers Certification Bodies to carry out the following procedures:

  1. Inspect & Map the product’s manufacturing
  2. Technically assess test data generated by compliance testing conducted by an independent testing laboratory accredited to conduct the requisite tests
  3. Conduct surveillance audits at manufacturing premises to ensure repeatability of product performance
  4. Issue a certification marking and maintain a directory (Online) of the certification information.

After seeing the extent to which a simple hardware as a hinge is specified as per the its application you can appreciate the need of a “third party certification” scheme which helps assure system designers and manufacturers that their systems will perform to desired levels.

Having a third party product certification is the key to assure quality at the Product Manufacturing level.

QUALITY CHECK OF “SYSTEM DESIGN AND EXECUTION”

Every project is unique and quite often structures & systems designed call for modifications in materials and components purchased to build it. Most of the time systems like Facades, Fenestrations and partitionsare uniquely designed for each project. To ensure that tested and certified products and materials will perform in the unique environment; systematic testing is required.

The geographical and climatic environment the building is being erected is akey factor influencing the specifications of compliance of each element of the building. As an examplethe illustration below showstwo different project specifications. These two will call for different approaches of material usage as well as testing to check quality.

Project 1
1. Structural Performance Test
Test pressure
Acceptable Deflection
AS/ NZS 4284-95
1.6 kPa
L / 240 or 20 mm
2. Air infiltration test
Test Pressure
Permitted Leakage
AS/ NZS 4284-95
300 Pa
3.6 m3/hr/m2 (1.0 L/s/m2)
3. Static Water Penetration Test
Test Pressure
Leakage Details
AS/ NZS 4284-95
300 Pa
No water penetration on interior surface
4. Cyclic Water Penetration Test
Test Pressure Cycle 1
Cycle 2
Cycle 3
Leakage Details
AS/ NZS 4284-95
150 – 300 Pa
320 – 640 Pa
480 – 960 Pa
No water penetration on interior surface
5. Structural Proof Load Test
Test Pressure
AS/ NZS 4284-95
2.4 kPa
6. Seal Degradation Test AS/ NZS 4284-95
Project 2
1. Air infiltration test
Test pressure
Permitted leakage fix wall
Permitted leakage window
ASTM E 283
600 Pa
1.5 m3/hr/m2
2.0 m3/hr/m
2. Static Water Penetration Test
Test Pressure
Leakage Details
ASTM E 331
600 Pa
No water penetration on interior surface
3. Structural Performance Test
Test Pressure
Acceptable Deflection
ASTM E 330
+ 2.67 kPa
– 3.40 kPa
L/200 or 20 mm whichever is less,
4. Dynamic Water Penetration Test
Test Pressure
Permitted leakage
AAMA 501.1-05
600 Pa
No water penetration on interior surface
5. Seismic Test
Horizontal displacement
(+/-) 14 mm from normal position
6. Air infiltration test AS/ NZS 4284-95
300 Pa
3.6 m3/hr/m2 (1.0 L/s/m2)
7. Static Water Penetration Test AS/ NZS 4284-95
300 Pa
No water penetration on interior surface
8. Hose Test AAMA 501.2-09
9. Structural Proof Load
Test Pressure = 1.2 X design load
Acceptable Deformation
ASTM 330
+ 3.204 kPa
– 4.080 kPa
L/1000

At this stage of the project therepresentative mockups of sections of Curtain Walls, Windows, partitions and other systems need to undergo tests which simulate the final conditions which are specified by the design consultants.

Tools to create evidence of compliance of systems and workmanship:

  • Breakdown the design to critical sub-systems to check the uniquely designed elements for known failures as per prescribed standards and limits set by the design consultant.
  • Test these sub-systems with uniquely designed and fabricated mockups that simulate the project environment. Test standards specify methodologies of testing and data capture.
  • Use on-site testing to arrive as proof of compliance of the final work at the site.
  • Utilize (if available) technical opinions (Assessments) to extrapolate existing test data to prove compliance with certain modifications.
  • Conduct inspections to correlate the workmanship of fabrication system erection.

Points worth noting while conducting such tests:

  • The mockups should be erected by the same subcontractors and using the exact same design and materials which will be later deployed at site.
  • The inspectors reviewing final work done at site should refer to test reports which have captured the design, material and method of fabrication to check the workmanship of the final work.
  • Careful attention should be given to the design. The stakeholders should not attempt to achieve compliance to under or over specified requirements.
  • The third party testing or inspection agency should have appropriate accreditations to conduct the requisite tests.

This system level Quality Check is most prone to short cuts. Design Consultants and Governing Authorities (like fire departments, Public Works Departments, Municipalities, etc.) are the guardians of Quality. They set codes, guidelines and criteria of acceptance of buildings and their performance. These guardians can be tough or lax in their monitoring processes.

Conclusion:

With increased awareness amongst developers, owners and users there is an increased level of understanding for quality checks and the availability of the right tools and processes brings about a promise for more accuracy in curtain wall performances.

The above elaboration aimed at making quality checks more quantifiable. Empowered with correct knowledge and equipment the stakeholders can be mindfulof the pitfalls and false quality claims.

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