Windloading & Undertile Membranes

The most important environment factor which affects the satisfactory performance of roofs is wind gusting.

During short-term wind gusts, pressure differences occur between the roof space (loft) and the outside of the roof covering. The result is a wind force that causes the total or partial removal of the roof covering allowing further damage by natural elements.

Roof pitches below 30° results in suction on both the windward and leeward sides of the roof. This suction or lifting force, particularly on a low pitched roof, is often the most severe wind load experienced by any part of a building. Under strong wind gusts the uplift on the roof covering may be far in excess of the dead mass of these coverings, requiring both the roof covering and the total roof structure to be securely fixed to prevent the roof and/or covering from being lifted and torn from the building.

Wind tunnel tests and practical evidence have shown that the satisfactory performance of a roof, and a tiled roof in particular, depends on the complementary function of the roof covering and the undertile membrane.

A suitable roofing undertile membrane will afford:

1. A suitable roofing undertile membrane will afford:
2. Reduced dust contamination in the loft space, hence allowing it to be utilised as a storage area.
3. Minimised water ingress and damage resulting from hailstones melting in valleys, concealed gutters, etc.
4. Protection against roof leaks in the event of damage to the roof covering. The working performance of the roofing undertile membrane substantially reduces the lifting forces on the roof covering. In addition the undertile membrane brings definite advantages to the building. In essence an undertile membrane is an essential component of a pitched roof and should be considered an investment and an insurance for a weather-tight roof. If a roof structure is fitted with an undertile membrane of suitable quality and is tiled according to the required specifications, it will withstand excessive wind speeds.