If your felt roof is over 15 years old the chances are that it will need renewing soon. Tell-tale signs are blisters and cracks on the surface. When to renew it, depends on how much you value what is below the roof. A garage roof is less critical than an extension on your house but bear in mind that damage occurs as soon as water enters a building. A roof covering needs to be waterproof, to keep out the weather, flexible to cope with building movements and still be porous enough to allow the roof to breathe. In other words, it should be like your skin. Pitched roofs with slates or tiles which act like scales on a fish, accomplish all of these, but are useless on a flat roof.
So….what
should you use to re-cover your roof?
Felt is the cheapest but is seriously affected by U.V. radiation. With increasing U.V. rays passing through the thinning ozone layer, even the more expensive elastomeric modern felts are unlikely to last more than 20 years.
Metal roofs are too rigid to accommodate building movements over time and suffer from corrosion. Fiberglass roofs are similar to metal roofs, becoming even more inflexible as plasticisers break down under U.V. radiation. Various P.V.C. systems are available which are fairly long lasting but also suffer from leaching plasticisers. The environmental and health related benefits of “Building without P.V.C.” are highlighted in the Greenpeace report.
Costing much the same as a
quality felt roof. Firestone E.P.D.M has recently become available to
the domestic market. Firestone are the world’s biggest manufacturer of
E.P.D.M. (a synthetic rubber similar to heavy-duty pond liner) and are
famous for not only tyres, but also high performance roofing systems for
commercial buildings.
E.P.D.M. is unaffected by U.V. radiation (tested to 50+ years), is very flexible (over 300% elongation) is vapour permeable (allowing trapped moisture below to evaporate through membrane), can be simply laid on top of existing covering giving a fast effective installation without mess and a superior weatherability.