Red Book FAQs

Red book FAQs

The scientific justification of the ACR test and Factors of Safety

The background to the ACR test is decribed in the report “Human Impact Loads On Roofs” by A. Maitra. Details of the factors of safety implicit in the test can be found in paragraph 16.


Application of the ACR Test to glazed assemblies

Following the publication of the Red Book (ACR[M]001:2000) ACR has been asked several times about the application of the test to glazing. The correspondence has, predominantly, come in two forms:

  • A comment that the test should not apply to glazed assemblies, and
  • A question asking whether it applied to glazed assemblies and, if not, why?.

The Committee always responds as follows:

When the ACR developed the test, there was no input from the glazing industry. Consequently, the ACR were not aware of the special circumstances, which may be connected with glazed assemblies. Therefore, the ACR test does not require any preliminary drops of sharp low-weight objects onto the assembly1. Neither does it require any post-test loading of the impacted assembly2. This is because on most industrial types of roof, rescue of the fallen person would be possible without going on to the damaged assembly.

Note 1: Impact of sharp low-weight objects, eg, tool-boxes dropped on end, can have a significant effect on the impact strength of glass.

Note 2: On industrial roofs, the purlin spacing is unlikely to exceed 1.8m. This means that a person who has fallen and cannot self-rescue, can be rescues by someone working entirely from an undamaged area of roof.

With many glazed assemblies, the spacing of the supports is much greater, which means that the rescuer could have to work from within the damaged area.Therefore, the ACR recognises that the test, as specified, may not be applicable to glazed assemblies.

However, ACR would stress the point that the drop test specified in the Red Book represents the forces that a 100kg person falling from standing to seated would apply to the surface he/she has fallen on. This force would not be different for glazed assemblies and should be the one that is applied as the definitive test for non-fragility, regardless of any additional requirement to pre-test and post-load.

The background to the development of the ACR test can be found in the report “Human Impact Loads on Roofs” . Readers are also advised that a working group sponsored by the Centre for Window and Cladding Technology [CWCT], in Bath, is developing a test applicable to glazed assemblies [Technical Note TN 42].


Application of the ACR Test to GRP Rooflights

The NATIONAL ASSOCIATION OF ROOFLIGHT MANUFACTURERS (NARM) have produced a GUIDANCE NOTE (ref:2004/1 -Test for Fragility of Roofing Assemblies (ACR[M]001:2000) – Application to GRP Profiled Rooflight Sheeting)

This Guidance Note sets out guidelines on the application of ACR[M]001:2000 -Test for Fragility of Roofing Assemblies ( the Red book) to GRP Profiled Rooflight Sheeting, together with recommendations for GRP sheet weights to use in order to achieve the desired levels of performance in various applications.

A copy of the guidance note can be can be found at


How should the Red book test be referenced in manufacturers literature

The ACR recommends that the correct and preferred method for manufacturers/suppliers to use to reference the Red Book test when referring to the  non fragility aspects/classification of their products is :

Tested and Classified to ACR(M) 001: ( insert year/version number of the red book used for the actual  testing) Red Book ( compliant with the current edition).”

The actual test originally defined in  ACR (M) 001: 2000 has remained unchanged throughout each subsequent revision of the Red Book – the various revisions merely seek to clarify aspects of the interpretation of it’s correct application.

When a new version of the Red Book is issued it automatically supersedes the preceding version which becomes obsolete and is withdrawn.

The latest version of the Red Book WILL always be used to validate any claims regardless of which version was current / used at the time of actual testing. When a new version of the Red Book is issued manufacturers MUST check that the interpretation of the Red Book used at the time of testing is still valid in accordance with the new version.

If the interpretation is still valid then the products may continue to claim compliance to the Red Book without further testing.

If the interpretation used is invalid then compliance with the Red Book may no longer be claimed and retesting must be done using the correct interpretation as detailed in the latest version of the document.

Note: By claiming compliance with the Red Book all manufacturers and suppliers MUST accept and agree to these stipulations otherwise the ACR will withdraw it’s permission for any reference to it’s publication/test being used by them.

The ACR recommends that the preferred method of reference indicated above should be used in any future publications/ material.

Existing printed literature which contain a wrong method of reference  may continue to be used but should be revised to use the preferred reference method as soon as reasonably practicable.

The ACR recommends however that more easily amended transient publicity material such as websites, adverts, flyers etc. should be brought up to date as soon as possible.

Note: Merely using a wrong method of reference  does not invalidate the classification claim of any product provided the above principles & requirements are met and should not give cause to raise a complaint against the product under the ACR complaints procedure. Where a wrong method of referencing is found being used Clients/Purchasers should satisfy themselves, by enquiry to the manufacturer/supplier, that the above procedure has been carried out.

[See also ACR’s Legal Page  re acceptable use of the Red Book]

Complaints procedure

In order to ensure that spurious claims concerning conformity with it’s material standard do not lead to unsafe assemblies being installed, the Committee has established a complaints procedure to validate suspect claims of non fragility classifications made by manufacturers, installers and suppliers of roofing products.

It is an requirement of the Red Book that anyone claiming compliance with that material standard must be able to state the ACR classification of the assembly specified and on request provide all the test data to support that classification.

If anyone considers a suspect claim is being made they should initially request the test data from the supplier to satisfy themselves that the required tests of the standard have been carried out.

NOTE: The red book requires that all the test data that led to the product’s claimed classification be made available on demand to anyone who requests it.

If they still consider the claim of non fragility is suspect or are unable to obtain the test data to satisfy themselves about the product, they may refer the matter, in the first instance, to their own ACR Trade Association which initially deals with the material in dispute.

[If they are not in a Trade Association they may refer the matter to any of the Trade Associations which make up the ACR [that Trade Association will then forward the matter to the most appropraite ACR Trade Association – usually the one with the most knowledge of the product material being used – to inquire into the matter.]

However if that Trade Association’s inquiry is unable to solve the issue and it considers that the complaint warrants investigation it may formally request the Committee to investigate and validate the claims made by the supplier.

The formal validation procedure agreed by the Committee is shown in the  flow chart:

Note: Any decision made by the ACR in any matter relating to how this complaints procedure is operated or interpreted, including any outcome is final. Additionally please see the FAQ relating to “acceptable use of the Red Book” and how it should be referenced in publicity

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Please note the primary remit of the ACR is promoting roofwork and roof safety - the Committee only accept questions relating to its work and it’s publications. If your question relates to roof or roofwork specifications or products, or site specific /general roofwork and roof safety issues not covered in our publications, you are asked to contact the various constituent Trade Associations who made or install the products - links to their web pages can be found here.