ALTERNATIVE TEST METHODS FOR ACHIEVING NZBC C GROUP NUMBERS
MBIE document Building Controls Update 147, Achieving NZBC Group Numbers for surface finishes from tests to overseas standards covers fire test procedures for establishing the Group Number as required by NZBC C/AS1-AS7.
These are either:
a) ISO 9705: 1993, which is a full-scale room corner-test, or
b) ISO 5660: 2002, which is a bench-scale fire test on a small sample of the material.
The MBIE document then goes on to discuss a European Standard for establishing the Group Number that is not cited in NZBC C/AS1-AS7 (or VM2), EN 13501-1:2007 Fire Classification of Construction Products and Building Elements - Classification Using Test Data from Reaction-to-fire Tests. EN 13501-1 is sometimes referred to as the Euroclass System for reaction-to-fire test, or just Euroclass. EN 13501-1 does not use Group Numbers but classifies results as A1, A2, B, C, D, E and F (from least to most combustible).
MBIE also discuss that in Australia Group Numbers are derived from AS ISO 9705:2003 which is an identical reproduction of ISO 9705:1993
They go on to say that the co-relation of wall and ceiling surface finishes derived from Australian or European classifications to the Group Number requirements of NZBC Clause 3.4(a) can, without the need for further testing, be taken as described in the following table.
| New Zealand Group Number according to NZBC Clause C3.4(a) using ISO 9705:1993 || Australian Group Number according to NCC Specification C1.10 Clause 4 using AS ISO 9705:2003 || European Classification using to EN 13501-1:2007 |
| Group Number 1-S || Group 1, and a smoke growth rate index not more than 100 || Class A1, A2 or B and Smoke production rating s1 or s2 |
| Group Number 1 ||Group 1 |
| Class A1, A2 or B |
| Group Number 2-S || Group 2, and a smoke growth rate index not more than 100 || Class C and Smoke production rating s1 or s2 |
| Group Number 2 || Group 2 || Class C |
| Group Number 3 || Group 3 || Class D |
| Group Number 4 || Group 4 || Class E and F |
What does all this mean?
If a product has been tested to EN13501-1 or AS ISO 9705 and gives the result you need from the table, the resulting Group Number would still be an Alternative Solution, but one convincingly supported by MBIE's own document.
We hope that this sort of sensible approach to overseas Standards makes it into the Code.
Two other points to the MBIE document are worth noting, these are:
· (1). Some products, especially those from Australia, may have been tested to AS/NZS 3837. This is the same test as ISO 5660 but with different end-of-test criteria, which means for some materials this may affect the assessment of a Group Number.
· (2.) A test result for a material or coating applied to a particular substrate may also be used for the same material or coating applied to another substrate of the same or less reactive type (refer Table A2 NZBCC/VM2) provided the new substrate is of equal or greater density. For solid timber, the material or coating may be used on other solid timber of equal or greater density and thickness. Notwithstanding this, proprietary coatings must only be used as recommended by the manufacturer.
Finally we understand there may have been some confusion over when the new website version of Building Controls Update 147 and its associated Guidance document were published and the publish dates on the original documents. This should not affect the use of this document in the future.
Check out Building Controls Update 147, Achieving NZBC Group Numbers for surface finishes from tests to overseas standards.