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Choosing roofing materials suitable for the UK climate

Written On by RTA Member

The UK already experiences some of the harshest weather conditions of the whole of Europe. Climate change means that severe weather events are likely to increase in the future; such as flooding, droughts, heat waves, severe gales and snowfall. The amount and frequency of rain will change, with winters becoming wetter and summers being hotter and more prolonged.
Not only is a pitched roof the primary means of protecting a building against the elements, it also accounts for around a third of the visible area of the building. It is therefore important that roofs are properly designed, with attractive, sustainable materials and well maintained. When re-roofing, aside from buying a house, a new roof represents one of the most important investments most of us will make, so it is vital to know when a roof needs attention and, if so, what should be done about it.
RTA members develop clay and concrete roof tiles and associated roof systems with the UK climate very much in mind. All their products are subjected to comprehensive testing by RTA members themselves, as well independently by bodies such as BRE and Lucideon.

The following are some of the key requirements RTA members believe are important for good quality roof tiles suitable for the UK climate.

Frost resistance
In an average UK winter there may be many freeze/thaw cycles, particularly when the temperature drops below freezing at night then rises above freezing during the day; sometimes this may go on for several weeks. Often, this coincides with wet weather, meaning tiles may be saturated as the temperature cycles between freeze and thaw. These conditions represent the harshest test of a clay tiles’ durability.
By contrast, tiles installed in colder countries may not experience many freeze/thaw cycles because the temperature can stay below freezing for long periods. Similarly, warmer countries may not experience any freeze/thaw cycles at all during an average winter.
EN 1304: the European Standard for clay tiles, has three pass levels for freeze/thaw resistance. Clay roof tiles used in the UK must pass the highest category: 150 cycles, when tested in accordance with the frost test method detailed in EN 539-2: the European Standard test method for frost resistance. In other areas of Europe, clay tiles only need pass 90 or even 30 cycles to be considered suitable for some areas. Therefore, it is important that tiles intended for use in the UK have passed the highest test level.

Wind and rain resistance
Predicted wind speeds for Europe, based on historical meteorological data, are given Eurocode EN 1991-1-4: 2005. However, the means of interpreting these wind speeds into actual load forces on pitched roofs in the UK is given in British Standard BS 5534. RTA members, who really understand the UK climate, are therefore ideally placed to provide properly calculated roof tile fixing specifications for their roof tiles and roofing systems. It is also important to use the fixings supplied by the roof tile manufacturer to ensure reliable wind resistance and compliance with BS 5534.
Most climate change predictions indicate increases in rainfall in the UK, and, more significantly, increases in the intensity of rainfall events. Therefore, well designed roof tiles and systems are a must to ensure long-term durable and weathertight solutions.
RTA members regularly subject their roof tiles to vigorous wind-driven rain testing, using the methods and conditions specified in European Test Report TR EN 15601. This document provides testing conditions applicable to the UK, meaning that roof tile manufacturers can design and assess the suitability of their tiles for use in the UK.

Installation Standards
Whilst the Standards for manufacturing clay and concrete roof tiles are European, the Standards and good practice for roof design and construction are British. These include BS 5534: Code of practice for slating and tiling, BS 8000-6: Code of practice for workmanship on building sites, BS 5250: the Code of practice for prevention of moisture in buildings and BS 8612: Standard for dry fix ridge, hip and verge systems.
RTA members are ideally placed to understand appropriate UK roof design for pitched roofing products and systems and can provide comprehensive fixing recommendations and architectural specification clauses for each roof element.
Similarly, by using dry fix ridge, hip and verge systems supplied by RTA members, users can be certain that these systems are fully compatible with the roof tiles and are designed and manufactured to be fully compliant with BS 8612: Standard for dry fix products.

Summary
To ensure your roof tiles and associated products and systems are suitable for the UK climate and will remain weathertight and durable in the long term, always consider using products from RTA members, who are able to provide technical advice and assistance if needed.

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