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

Roof Support Structure

The roof structure must follow a specific project that takes in consideration the materials used and the type of structure planned. 

The most commonly used structures are made of wood, concrete, stone and some mixed solutions resorting to metal profiles. The picture below shows examples of structures with and without insulation.

Wood structure

Stone and concrete

Stone, concrete and metal
profiles structures

The materials used in the structure are irrelevant to the proper performance of roof tiles. The constituting elements must fulfil their function. The roof tiles will be supported by those elements and fulfil their role.

Latch work

Laths are the simplest element of a roof structure. Roof tiles are laid on laths. Laths can be made of pine, concrete, pre-strained beams, metal profiles, PVC or mortar on stone slabs.

Lath spacing is the distance between the upper part of a lath and the lower part of the next lath.

While the roof tile maker should indicate lath values, these are merely suggested, as the actual spacing should be calculated at the construction site in accordance to the tile type, as referred in the section of this manual concerning the laying of each tile type (Lusa, Marselha, Milénio and Canudo).

Executing the lath work

Once lath spacing is calculated, the execution of the lath work must take the following aspects in consideration:

Dimension and shape of the lath

If using a prefabricated lath made of wood, PVC or other, it willl usually come in a rectangular shape with approximately 4x2cm and can be fixated by using screws or galvanized nails; if using metal profiles, fixation can be conducted by welding with na anti-corrosion treatment; for pré-strained beams, fixation is done by using mortar.

If the lath is done in situ (with mortar) it should have the following shape and dimensions:

1. Base: 10cm
2. Height: 3cm

Laths applied on a slab or directly on the insulating element should be spaced to allow ventilation of the lower side of the tile, to avoid the appearance of air chambers between rows.

For more details and instructions regarding ventilation of roof tiles, please consult the section of this manual concerning the laying of roof tiles (Lusa, Marselha, Milénio and Canudo).

Applying the first lath

If the roof does not have eaves but includes a gutter, the following scheme should be followed:

1. 1st lath
2. 2nd lath
3. 3rd lath
4. Lath spacing

When the roof includes eaves, the procedures described in the section of the manual concerning the laying of tiles (Lusa, Marselha, Milénio and Canudo) should be followed, specifically those referring to the application of accessories.

Considerations when planning the roof

One of the most frequent situations faced on building sites is the need to cut pieces to finish the roof. Cutting pieces should be avoided, both for aesthetical and technical reasons (cutting pieces may negatively affect roof performance).

Thus, it is convenient that the roof plan reduce the need to cut pieces to a minimum. The following picture shows an example of a roof where the architectural project took into consideration the adequate use of whole pieces.

1. 8 whole pieces
2. 3 whole pieces