Absence of proper roof ventilation might sometimes compromise the whole building. For inclined clay tile roofs, there are two possible types of ventilation:

Ventilation of the underside of roof tiles or Micro-ventilation

Ventilation of the underside of roof tiles is essential for the proper performance of a roof. Air circulation dries rainwater absorbed by the roof tile, avoiding condensation and the appearance of moss.

In areas subjected to high thermal variations, proper ventilation ensures higher resistance to peeling as a result of the frost-defrost cycle, as can be seen in the picture below:

marselha-vento-vapor-chuva This type of ventilation helps in:

  • Eliminating water vapour produced inside the dwelling;
  • Prolonging roof tile durability;
  • Improving roof tile durability against ice and frost;
  • Preserving the lath work, if it is made of wood;
  • Reducing heating by convection during summer.

It is therefore necessary to ensure there are air vents in place on the roof by means of:

marselha-telhas-ventilacao

  • ventilation tiles (minimum 3 per 10 m2); ventilation tiles must be unevenly placed near the eaves and ridge;
  • air vents near the eaves;

However, so that air can circulate, there must be free space under the tiles (2 to 4 centimetres), corresponding to the standard size of laths. Laths, on the other hand, must be interrupted for 2 to 3 centimetres at alternate points each 3 to 4 metres to allow air circulation, as shown in the picture bellow.

marselha-ventilacao-ripado

Ideally, counter-laths will be placed where laths are laid. Counter-laths should have at least 2,5 cm, so as to allow air circulation, as exemplified in the picture bellow.

marselha-contra-ripa Legend:
1. Slab
2. Counter-lath
3. Lath
4. Roof tile


In any case, ventilation should always be enhanced by applying ventilation tiles, as will be discussed later in this manual.

Roof performance can always be improved. However, performance is intimately linked to the roofing project. While at the project phase, it is necessary to carefully consider the materials to be used, how to apply them and the technical qualifications of those applying them. Choosing the best materials will never substitute their proper application.

Garret ventilation

The garret of a roof must always be ventilated. This ventilation will ensure the durability of materials, thermal comfort in summer and a dwelling’s habitability.

If the garret is not used as a living space and the structure is not continuous, ventilation will be performed by the entry of air through the roof, as by wind.
If the garret is used as a living space or similar, where hygienic conditions must be ensured, then some care must be taken, especially if using wooden panelling. In this case, insulation should be applied directly over the panels, and roof tiles must be laid over lath; the space between the insulation and the roof tiles must be ventilated. If the structure is not continuous, insulation does not have to be continuous either. For more details regarding the application of insulation, see that specific section.