Fitting a roof

The roof covering composition has several roles:

• To provide a rainproof cover and guide water away sensibly
• To stop wind penetration
• To insulate the building
• To stop condensation forming

The components of a roof structure are shown in the diagrams that follow:

Generally the layers of the roof (progressing from the outside) are:

1. Roof tile.
2. Underfelt.
3. Ventilation path from eave to ridge.
4. Insulation.

The insulation may be over, between or indeed under the main supports (rafters or trusses).

The ventilation path may be over the top of the underfelt if a breather felt is used (it should be these days).