Wind related damage

There are a number of potential problems that may be experienced by flat roofs because of the effect of the wind. They are discussed below. (The general background to this subject is discussed in Chapter 7 in the section entitled 'Wind-related damage'.)

THE EFFECT OF SUCTION. As with pitched roofs, negative pressure (suction) is a greater problem than positive pressure and affects the edge of the roof (the eaves and verges) more than the central area of a flat roof. This is because maximum suction occurs at the edge, although flat roof coverings that are particularly light in weight may be prone to lifting by suction across their whole surface area. Any weakness in the (edge) fixing is exploited by the wind and may lead to the covering being lifted. Multi-layered roofs can experience successive removal of the individual layers of the roof, eg covering, insulation, decking, sub-structure. At its worst, it is not unknown for a complete flat roof to be physically removed as an integral unit from the top of a building and deposited some distance away.

SCOURING ACTION ON PROTECTIVE DRESSINGS. The wind can have a scouring action on any gravel covering used as a protective dressing on a flat roof. Loose ballast of less than 20mm diameter on inverted roofs may be particularly affected, leading to damage of the underlying substrate. The movement of the dressing may also result in the exposed roofing material being degraded by ultraviolet light, drainage out-falls becoming blocked, injury of pedestrians or damage to adjoining glazed areas, especially where there is a lack of any raised parapet walling.

PRESSURE ON LAPS, JOINTS AND STEPS. A wind speed of 26 metres per second is not unusual in the UK and is often exceeded (this wind speed is described as 'storm' on the Beaufort Scale, which indicates wind force). Such a wind speed, which is becoming more frequent due to climatic change, will support a 50mm column of water. Therefore, any welted or folded joint or seam, any upstand or step, that is less than this height must be viewed with suspicion as there is every possibility that it will leak under high wind conditions.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment