Accessories (for roofs)

Complementary pieces for roofing.


Formed through the disaggregation of feldspar rock that becomes malleable when wet. Argil can be found near riverbeds, often forming banks along the margins. Argil can be white, red, gray and brown. It is composed mostly of hydrated alumina sillicata - - Al2O3 · 2 SiO2 · 2 H2O, has low cristallinity and minute dimensions (particles under 2 µm in diameter). Mineralogically, its main components are quartz, illite, caulinite, anatase, hematite and feldspar.


Same as fracture.

Clay tiles

Products for non-continuous application on inclined roofs and wall linings, made by standardizing processes (extrusion and/ or pressing), drying and baking prepared argil, with or without additives.

Construction products

Products to be used or applied permanently in construction projects.


of composing elements (roof tiles and accessories)


Structural defect that consists of a gap with a more or less regular shape affecting the thickness of the piece and is visible to the naked eye.

Distance between laths or gauge

Length of the exposed part of a roof tile or accessory, measured longitudinally.


Edge of a roof along the outer part of a protruding roof slope, made of roof tiles


Edges of a roof along the outer part of a roof slope, projecting beyond the side of a building and composed of accessory pieces.

Effect of ice

This term refers to the wear caused on roofing pieces by successive frost-defrost cycles.


Type of coating, permeable or impermeable, or the material used therefore.


Production process.


Crack with a more or less regular shape that does not affect the whole thickness of a piece.

Fixation orifice

Open or easily pierced orifice for the fixation of a product on the support structure.


Structural defect that consists on the breaking of a product into two or more fragments.


Space under a roof slope

Gutter / Joist

Concave, open piece, usually made of metal, through which liquids run, placed horizontally along the eaves of a roof to drain rainwater, thus avoiding infiltrations.


Property of materials relating to their capacity to absorb water. Ceramic materials are less hygroscopic than concrete or mortar.


Secondary structural piece of a roof arranged in a perpendicular line in relation to the highest inclination of a roof slope, where coating elements are supported.


When used in relation to flat or fitting roof tiles, the value of linearity is given by the deviation in a straight line as measured from the roof tile brim, both longitudinally and transversally.
For Canudo roof tiles, linearity is given by the deviation in a straight line as measured along the generating line at the bottom of a roof tile’s concave end.

Mechanical resistance to flexion

This test is conducted by applying an increasing force on a roof tile until it breaks. The value registered at the breaking point indicates the flexion of the roof tile.

Outeiro da Cabeça

Village located 18 Km from Torres Vedras.
The village covers an area of 5,7 Km2 and has a population of 932 inhabitants. Its main economical activities revolve around red clay ceramic industries (roof tiles and bricks) and agriculture.


 PDM: Municipal Master Plans (Portuguese).


Fixation orifice that is not fully pierced through.

Recommended overlap

Roof tile length that must be overlapped to the next roof tile.

Roofing functional demands

Minimum criteria to be met by a roof. The proper performance of any roof depends on three main factors: correct conception at the project stage, good individual performance of clay pieces and their correct application on the roof.

Roof slopes

Where joists are placed.

Roof tile fixation

Use of nails, screws, metal hooks or any other auxiliary fixation mechanisms that prevent pieces from moving.

Roof tile gap

Gauge or distance between laths.


Also known as pitch or roof surface; any flat surface of an inclined roof.


Surface defect over 7mm on average, consisting of a fraction of the material, separated from the ceramic body on the visible side of the product.

Support spindle

Relief at the underside of a roof tile or accessory allowing its fixation on the support structure, generally consisting of laths.


Colour shade variation on the same make of pieces.

Transversal profiles

This term is applied to Canudo roof tiles and refers to the width of its internal edges.

Underside roof tile ventilation

Also known as micro-ventilation; this refers to the circulation of air near the underside of a roof tile. Aids in the drying of absorbed rainwater and eliminating water vapour from inside a building, which could otherwise condensate on the underside of the roof tile; also aids in the conservation of the lath work, when it is made of wood. Improves roof tile resistance to the effect of ice.


Air circulation process.


In this context, the term relates to the capacity of a roof to completely prevent the entry of water. Impermeability of the clay material used and total roof coverage must be ensured, as well as the correct inclination of the roof. Wind and rain, which in conjunction can provoke ascending water movement along the roof surface, are a serious challenge to the watertight qualities of a roof.

Technical Support

Normative Demands

Clay tiles and accessories must comply with several norms defining the minimum requirements necessary to guarantee their usability in accordance with the performance specifications declared by the maker.

Norm NP EN 1304 – clay roofing tiles and accessories – Products definitions and specifications is the reference norm for this, as it describes the main requirements such products must comply with, cross referencing other norms essential to their proper application.

Structure and fixation characteristics

These products should not have manufacture defects that prevent their joining, nor structural defects such as cracks or gaps.

Roof tiles and accessories can be produced to accommodate fixing pins and/ or fixation holes, but other fixation methods are also permitted.

Geometric characteristics - NP EN 1024

All testing methods to determine conformity with the technical specifications defined can be found in norm NP EN 1024.

The compliance of roof tiles with these requirements is essential to the correct execution of roofing work.


The dimensional stability of pieces is one of the key aspects of their individual characteristics. In the case of longitudinal and transversal fitting roof tiles, the stability of length and width must be ensured. A dimensional variation of ± 2% over the values declared by the maker is, however, acceptable.

In lieu of individual values, the maker can declare the coverage area dimensions. In this case, the average measured value must not present a deviation of more than ± 2% over the values declared by the maker.


Planarity is one of the main characteristics regarding the regularity of the shape of products. The planarity coefficient is expressed in percentage. The maximum allowed values for the planarity coefficient are 1,5% and 2,0%, depending on whether the roof tile length is superior or equal to 300mm or inferior to 300mm, respectively.

This however does not apply to Canudo roof tiles, whose uniformity is not measured in terms of planarity, but rather by their transversal profiles, i.e., the measurement of the width of tiles at their narrower and wider sides. In both cases, the difference between the largest and smallest width values must not exceed 15mm.


Linearity is another key characteristic of pieces. The maximum admissible values for the linearity coefficient at 1,5% and 2,0%, depending on whether the roof tile length is superior or equal to 300mm or inferior to 300mm, respectively.

Physical and mechanical characteristics

Impermeability - NP EN 539-1

The impermeability of individual roof tiles and accessories is an essential functional demand and a contributing factor to the proper performance of the roof they are a part of. The impermeability of clay roof tiles and accessories must be classified as either grade 1 or grade 2; only the former may be used on roofs with no interior watertight coating.

The maker must declare the test method used (1 or 2) from those described in the norm, so as to evaluate conformity with this requisite.

Flexural Strenght - NP EN 538

Roof tiles must be able a certain load in flexure without breaking.

The values defined for each tile type are as follow

Torreense Roof Tiles   Flexural strength - NP EN 538
Marselha900 N
Canudo1.000 N
Lusa1.200 N
Milénio1.200 N

Frost Resistance - NP EN 539-2

Under certain atmospheric conditions roof tiles will be subjected to constant wear due to the frosting and defrosting of absorbed rainwater, especially when sudden temperature variations occur within a short time span. 

Thus, materials must comply with specific requisites when applied in areas prone to this sort of occurrence. The test method to evaluate roof tile conformity varies according to the country where they will be used.

In Portugal the C method is used; roof tiles must resist to 50 frost/defrost cycles with no defects.

Fire Resistance

Requisites relating to fire evaluate two main aspects: resistance to external fire sources and their reaction to fire. 

Clay products comply with the requisites relating to resistance to external fire sources, as they are in accordance with the definitions provided by Commission Directive 2000/553/EC.

As for reaction to fire, products comply with Class A1 requisites and do not require testing, in accordance with Commission Directive 96/603/EC.

Marking and Labelling

At least 50% of all tiles and 10% of accessories supplied must include an indelible and legible marking, either coded or not, that identifies the maker and the production unit, as well as the country of origin, the year and the month of production.

All documents supplied must refer to norm NP EN 1304, specify the impermeability class and the testing method used to evaluate this requisite, as well as the testing method to evaluate frost resistance (A, B, C or D).

Construction products

Decree nº 113/93 of 10 April has transposed European commission directive 89/106/CEE into Portuguese law, in order to homogenise the legislative dispositions regarding this matter across the Member States.

Directive 89/106/CEE is known as the Directive on Construction Products and aims to define procedures to adopt to ensure that construction materials are adequate to the end they are meant for, so that any undertaking falling under its scope complies with essential technical demands.

The Directive on Construction Products aims to ensure freedom of movement to all construction products within the Union by harmonizing national legislation regarding essential requisites concerning health, safety and well-being applicable to these products.

On 8 January 2007, Decree nº 4/2007 was published, introducing new adjustments concerning the updating of current terminology and the responsibilities of relevant institutions. One of its main goals was to clarify the mandatory addition of a CE marking on construction products.

EC Marking

EC marking can only be given to construction products complying with national legislation harmonized with European norms, that meet European technical approval regulations or, in their absence, that comply with national technical specifications that are in accordance with minimum essential requisites.

Essential technical specifications are defined by national norms resulting from transposition of a harmonized norm, i.e., a technical specification elaborated by the European Committee for Standardization (CEN), which, in the case of Clay Roof Tiles and roofing Accessories, is NP EN 1304. 

Thus, all materials with the CE marking meet the essential requisites as defined by the Directive on Construction Products. 

As for the certification of conformity, it is up to the makers to certify, by their own means or by a duly recognised certification organism that products comply with the requisites of a technical specification in accordance with the certification of conformity procedures as described by the Directive on Construction Products.