March 2020

Perfectly Pitched
This page and previous, clay roof tiles.
By reducing the thickness and weight of tiles, the
overall weight of material on a roof can be
significantly reduced. There are now many great
single lapped tile designs that closely resemble
traditional plain tiles and slates, meaning less
tiles are required, which in turn means less tile
battens are required, so the cost of materials and
installation times are significantly reduced.
Greater accuracy
The performance of roof tiles in resisting winddriven
rain has also vastly improved because of
greater accuracy within production and design
developments through wind tunnel testing,
particularly significant for roof tiles intended for
use at low roof pitches. A European wind-driven
rain test method was developed and, although it
has not been published as a British or European
Standard, it has been widely adopted as the way
to establish the weathertightness of roof tiles and
associated products such as ventilators. A
simplified method was also developed for testing
“The old ‘prescriptive’ tile fixing patterns for
single lap tiles have now generally been
abandoned in favour of more scientifically
accurate calculated fixing specifications”
dry ridge systems and this has been published in
the Dry fix Standard BS 8612.
Lastly, but just as important, improved
meteorological data, better understanding of
weather conditions and the way roof tiles react to
high wind loads has resulted in advances in tile
fixing methods. Standards are reviewed every five
years, with the latest weather data and new
understanding of weather patterns being
incorporated into roof tile fixing requirements.
This is particularly relevant with the weather
events we have experienced in recent years and
which are predicted to worsen and become more
frequent in coming years. The old ‘prescriptive’
tile fixing patterns for single lap tiles have now
generally been abandoned in favour of more
scientifically accurate calculated fixing
specifications, with all tiles fixed being a
minimum requirement. Roof tile clip technology
has improved also, with clips being more reliable,
easier to use and stronger in resisting the wind
uplift loads on the roof tiles.
In summary, much has changed in our traditional
clay and concrete roof tiles, though most of it is
unseen at a casual glance at the roof. However,
we still prefer our traditional roof tile shapes,
such as plain tiles, slates, pantiles and Roman.
Contact John Mercer
@johnmercer3
24 TC MARCH 2020