New flat roof – How to choose the correct roof membrane

By Robin Whitlock on January 6th, 2012

There are a number of materials available  for the construction of new flat roofs, including single ply membranes such as TPO (Thermoplastic Polyolefin), EPDM (Elastomeric membranes) and PVC, mastic asphalt and built up felt.

It will depend on the project involved, as to what type of material is utilised for the flat roof. Certain membranes are not suited to habitable buildings but are ideal for the construction of a flat garage roof, for example.

Most flat roofs have an average life expectancy of around 10 to 12 years. However, it will depend on how exposed the roof is to the elements.

Different types of flat roof membranes

TPO’s or Thermoplastic Polyolefin’s are closely related to other thermoplastic elastomers and are therefore properly called thermoplastic polyolefin elastomer’s. They have been appearing in construction projects since around 1990.

However, their use exploded when it was recognised their environmental benefits became apparent. Heat-weldable and reusable – especially if fixed mechanically or ballasted with pebbles or water – they do not pollute rainwater run-off and are durable, being highly resistant to UV, ozone and chemicals. This comparatively new product is untested over long periods and is derived from non-renewable oil.

EPDM (Elastomeric membranes) contain EPDM (Ethylene Propylene Diene Monomer), which is a form of synthetic rubber obtained through the polymerization of ethylene and propylene in association with ethylidene norbornene. Highly durable, it is reusable if laid loose or mechanically fixed and similarly does not pollute rainwater runoff.

A tried and tested durable roofing material, PVC – which is manufactured through a complex process which combines ethylene and chlorine to ethylene dichloride (EDC) – is not as environmentally friendly. Recently there has been concern over its effect on the environment, producing a move away from this material.

Other types of flat roof membranes

  • Mastic asphalt –  a mix of of limestone powder, limestone aggregate and asphalt, it contains bitumen which is formed from natural deposits or the distillation of crude oil.
  • Polymer-modified mastic asphalts – usually contain styrene butadiene styrene block copolymers which give flexibility and also some resistance to temperature effects. It is highly durable where provided with support and has been used for a long time.
  • Built-up felt – one of the most highly efficient materials, built-up felt features two or three layers of bitumen sheet, which is bonded with an adhesive or with hot bitumen. Despite being known for its waterproof ability, it is not particularly environmentally friendly.

Whatever the project, Builder Guide can help you to find a local recommended roofer to provide a cost-effective roofing solution to meet your needs.

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