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THE  EUROPEAN STANDARDIZATION
OF CLAY ROOFING TILES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

by Michel Albenque

Chairman of TC 128/SC3

December 2000

MA/ct

 

THE EUROPEAN STANDARDIZATION
OF CLAY ROOFING TILES

 

 

 

 

I - INTRODUCTION

Clay roofing tiles have been manufactured and sold from North to South and West to East in all European countries for centuries.

 

Traditional roofing products, clay tiles have developed taking a lot of different shapes according to the country of origin.

 

From the South of Europe to the North of Europe, the climatic stresses are quite different. Moreover clay tiles must give an answer to the various requirements of the consumer according to various codes of practice and local habits.

 

In this context, one can imagine that it was not, a priori, easy for "Standard" people to bring together, in a single document, so many different types of products and, of course, in a document which satisfies all the European users.

 

However, at the present time, clay roofing tile standardization work -voluntary stage- is finished and the different standards have been in application since the end of 1998.

 

 

 

II - ORGANIZATION OF THE WORK

For clay roofing tiles, the standardization work is carried out into Sub-Committee number 3 "Clay roofing tiles", which is a part of Technical Committee number 128 "Roof covering for discontinuous laying and products for wall cladding". The work was started in 1988 with the first meeting of the Technical Committee, in June, in Vienna, and the first meeting of the Sub-Committee N. 3 in December in Paris.

 

Till 1994, TC 128 and its Secretariat were led by Austria. Nowadays, Belgium with Mr Meert as Chairman, deals with TC 128. From the  beginning Sub-Committed N. 3 has been led in France by CTTB (Centre Technique des Tuiles et Briques) and the Secretariat handled by AFNOR, (the French body for standardisation).

 

Nearly, all CEE and AELE countries are present in SC3, except some Scandinavian countries.

 

 

 

SC3 has worked on clay tiles standards according to the directives set at the beginning by SCI "General requirements" which, after, has watched to the consistency of the documents prepared by the different sub-committee (SC2 to SC10) working on the different types of roofing products.

 

 

 

 

III - DRAFTED DOCUMENTS

More than 20, two-day meetings have been organized, country after country, in all represented countries. This gave the possibility to write the five draft standards programmed by SC3. At the beginning, the question was: What could be the frame for a clay roofing standard, only one document or several ? The answer was that a single document could not clearly deal with all families of tiles used to be produced in Europe and also deal with the description of the test methods.

 

After discussion, the accepted frame is :

 

- a standard for the definitions and specifications of all families of European tiles 

- three standards for test methods, one of them split into two parts as described by the following scheme.

 

        

 

 

 

 

IV - TECHNICAL CONTENTS

A clay tiles roof shall be :

- watertight

- durable

- pleasant to look at

- easy to built

and shall present a good security in normal conditions of use.

 

Of course, these requirements are fulfilled only when the roof is built according to the Code of Practice and with products that fulfil the standard requirements. Figure 1 illustrates the links between product characteristics and the requirements for the roofs.

 

When the list of the clay tiles characteristics involved in the behaviour of the roof was known, the remaining work was to draft the test method and to fix the level of the requirements.

 

The schemes enclosed illustrate the principle of the test methods :

 

 

EN 538    Flexural strength test consists of a verification of the ability of the product to resist a centred load when subjected to flexion on two simple bearers (figure 2)

 

 

EN 539-1   There ore two impermeability tests :

Method 1      (principle figure 3)

Determination of the amount of water passing in 48 hours through the ceramic body of the tile.

Method 2      (principle figure 4)

Determination of the length of time until drops of water start to fall, following the application of water to the surface of the tile.

 

 

EN 539-2

Concerning frost testing, according to the number of different methods in use at present in Europe and according to the various principles of the methods (unidirectional or multidirectional frost stress, imbibition under vacuum or at atmosphere pressure, frost of individual products or of complete roof), it has not yet been possible to state a single pan-European method.

 

 

So, the present draft describes four methods to use in accordance with a geographic zone (figure 5).

 

 

 

 

TECHNICAL CONTENTS

 

             

 

 

 

Figure 1

 

 

 

 

NF EN 538 - FLEXURAL STRENGTH TEST

 

 

 

Figure 2 - Test principle

 

 

 

539-1

IF  = cm³/cm²/day

(dimensions  mm)

 

Figure 3

 

 

 

 

NFEN 539-1

IMPERMEABILITY - Method 2

 

 

 

 

 

 

 

 

IC =    

x = Drop time of the first drop

 

Figure 4

 

 

NFEN 539-2

FROST RESISTANCE 

 

 

 

 

 

Figure  5 - Geographic areas of use

 

 

 

 

 

These four methods derive from respectively four national methods :

 

- Benelux method    Method A

- German method   Method B

- French method     Method C

- British method      Method D

 

 

The principle of these four methods remains the same ; it comprises of a soaking by water and the realisation of a certain number of freeze thaw cycles.

The differences between them consist of :

 

- a  more or less important water saturation

- velocity of the degrees of temperature decreasing during ice formation

- number of cycles

- unidirectional or multidirectional frost stress

 

 

Methods A and C specify a saturation under vacuum and a little number of cycles (respectively 24 and 50), methods B and D specify saturation at atmospheric pressure and a great number of cycles (respectively 150 and 100).

 

 

 

EN 1024

This standard describes the procedure to use to measure the geometric characteristics. These comprise  of:

 

- the dimensions (individual or overlap dimensions for interlocking tiles)

- the camber

- the twist

- uniformity  of the transverse profile of over and under tiles.

 

 

 

EN 1304

This standard gives precise definitions of the different families of European clay roofing tiles.

 

- overlapping tiles

- plain tiles

- tiles with side lock and headlock

- tiles with side lock only

- over and under tiles

- flat interlocking tiles

- clay roofing fittings

 

It specifies the requirement for :

 

- appearance and structure

- dimensional tolerances

- uniformity of the transverse profile of over and under tiles

- camber (*)

- twist

 

(*) Camber is determined as a relative variation between the arrow measured and the arrow declared by the manufacturer.

 

This allows the manufacturer to propose to the user tiles with special cambers.

For special tiles and fittings only few requirements apply.

 

 

V - EVOLUTION OF THE CLAY ROOFING TILES STANDARDS

   - CE MARKING

To transform EN 1304 into an h EN1304 (harmonised standard) TC 128/SC3 shall fulfil three tasks :

 

1°) Revise the voluntary part to make some requirements clearer (e.g. structural and surface faults) and to introduce some type of tiles which are not yet within the scope (e.g. over and under tiles with lugs).

 

2°) Revise the two standards EN 539-1 and EN 539-2 to propose a unique
pan-European method in both cases for impermeability and frost testing.

 

3°) Write the annexes ZA corresponding to the harmonised part of the standard in both cases to answer the requirements of mandate M/121 (Cladding) and mandate M/122 (Roofing).

 

 

At present :

 

1°) During its last meeting (June 2000), TC 128/SC3 agreed on a revised version of the voluntary part of EN 1304.

 

2°) A working group of TC 128/SC3 deals with both tests method

 

 

- Impermeability

 

There is reasonable hope in succeeding on getting a single test method based on the drop method amended to :

 

- give a good correlation with the volumetric method, which it is not the case at present.

- give a good sensitivity on low values of impermeability which is not the case at present.

 

 

 

- Frost testing

 

An important study is currently in progress to develop a single method, or a system of methods, comprising three levels of severity

 

- light

- moderate

- severe

 

The three levels could be based on a number of cycles to fulfil.

 

 

This study consists of two parts :

 

 - A practical study

 

Five experimental roofs have been erected in five European countries :

 

BELGIUM                          (severe

SWITZERLAND                  (climate

 

ITALY                             (moderate

FRANCE                          (climate

 

PORTUGAL                      (light climate

 

 

Some tiles are equipped with sensors to record temperature variations and express the velocity of decreasing temperature and the difference in temperature between the tile faces when the ice is forming.

 

Tiles are weighed regularly, so it is possible to know the water saturation when frost occurs.

 

 

 

- A study in lab

 

This part consists on developing a test method according to the recordings made on the experimental roofs.

It is hoped to finish the study getting a draft method at the end of the year 2001.

 

 

 

3°) Writing Annexes ZA

 

According to both mandates, the harmonised standard shall deal with the following characteristics.

 

 

M/121 ( Cladding)                                     M/122 (Roofing)

- Dangerous substances                     - External fire resistance

- Impermeability                                - Dangerous substances

- Durability (frost resistance)              - Mechanical resistance

                                                              - Dimensional tolerances

                                                              - Impermeability

                                                              - Durability (frost resistance)

An example of en Annex ZA is given hereafter.

 

 

 

Clay roofing tiles Annex  ZA to  EN 1304

according to M/122 mandate

 

 

 

 

 

VI - TASKS OF THE MANUFACTURER IN RELATION WITH CE MARKING

As for clay roofing tiles, the level of attestation of conformity is 4. The tasks of the manufacturer in relation with CE marking are :

 

à Realisation, by himself or in an external laboratory, of the type tests (according to the normalised test methods),

à Organisation by himself of a Quality production control : either by monitoring the raw materials, as well as the production or testing products.

 

- CE Marking

The following information and characteristics shall accompany the CE marking symbol  :

 

- Name and address of the manufacturer

- Last two digits of the year of CE Marking

- Dimensional tolerances (could be a declared value or satisfactory (*))

- The frost resistance (past/fail level ^(*))

- The impermeability (could be a declared value or satisfactory ^(*))

- The flexural strength (could be a declared value or satisfactory  ^(*))

 

These declarations, as far as we know at present, will meet the requirements of the CE Marking.

 

If the manufacturer wants to declare his production fulfils the requirements of the voluntary part, he will have to also declare:

 

- Dimensions

- Arrow (to control camber).

 

 

VI - CONCLUSION

For clay roofing tiles, European standardization has been an interesting exercise in which European manufacturers took part with, perhaps, a certain reserve at the  beginning. But confidence grew when people met after many times and the work became easier and, could we say,... amusing.

 

The end of the story is planned for April 2003, which means the adoption of EN 1304 as an h EN.

 

We can hope on getting a revised EN 539-1 with a single method for impermeability testing in 2001 and an EN 539-2 with a single test method or system in 2002, so the bet will be won.