Flat Roof Life Expectancy – some Examples

Last week we discussed what factors you should consider in choosing a single ply membrane, one of which was lifespan and track record.

The longevity of flat roofs is a popular topic, but what is sometimes overlooked is that the longevity of any roof is at risk if all design and construction elements are not of suitable quality.

The life expectancy of any roof depends on a number of factors including:

  1. The suitability of the construction for the site – have you considered the exposure?
  2. The life span of the waterproofing materials used – for example, not all slates are the same, and neither are membranes;
  3. The life span and suitability of all fixings and roofline materials. Have you chosen the right fixings and are there enough?
  4. Good detailing – including roof mounted plant, penetrations, etc;
  5. Proper installation and
  6. Appropriate maintenance.

Choose the right materials for the job, but don’t forget to choose the right designer and the right contractor as well.

Here are some unusual examples of flat roofing with a long life span.

Protecting Skara Brae – with long lived single ply membrane

Skara Brae is a stone built Neolithic settlement of eight clustered houses, 5000 years old, which can be found on the main island of Orkney. It is part of the World Heritage Site, ‘the Heart of Neolithic Orkney’, designated in 1999, and is one of the most popular tourist attractions in Orkney with as many as 60,000 visitors a year.


One of the houses, number 7, is the best preserved, and has been protected by a glass roof. However although the roof protected the interior from the worst of the weather, an unstable internal environment was threatening the preservation of a number of Neolithic carvings.

Historic Scotland, who are responsible for the protection of Skara Brae, asked FDT to help them protect the carvings in house number 7. Specialist contractors installed a new watertight garden roof over the whole of house 7 using the PIB membrane Rhepanol hg.

In one of the most inhospitable locations in the UK, a single ply membrane is helping to preserve an historic site, and because its lifespan is so long, it can be left undisturbed for up to 50 years.

Worlds oldest Single Ply Membrane – 50 years and counting

When it comes to a long life, the most reliable and credible membrane is PIB, the world’s oldest Single Ply roofing membrane.


In 1956 Prewanol (the predecessor of Rhepanol) was used to waterproof an 180m2 water treatment plant in Leopoldshafen, Germany. 50 years on in 2005 an inspection confirmed no significant damage and even the detailing to two integrated roof vents remained defect free.

The manufacturers, FDT, invited the State Material Testing Institute (MPA) to undertake an independent analysis of the membrane’s integrity including the welded seams. The results confirmed that the roof was still sufficiently waterproof and performing well.

Laboratory ageing tests have proven the longevity of synthetic roofing membranes, but evidence from an in-situ installation over 50 years old is much more convincing. If you’d like us to help you prove the case for a flat roof to your client or insurer, get in touch and we’ll be happy to assist.

Have you got an example of a longlived flat roof?

More information

Download Case Studies on Skara Brae and the 50 year old Water Treatment Plant.

Download more information about Rhepanol hg for green roofs our Rhepanol hg Downloads page

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