August 2020

Perfectly Pitched
CONSULTANT CASE STUDY: IN A FIX,
SECURE ROOF TILES CORRECTLY
In his latest consultant case study, Pitched Roofing Consultant John Mercer focuses on
roof tile fixings and discusses a new build site he was called out to where all was not
right on a number of properties…
There is now far greater clarity in the pitched
roofing industry about how roof tiles should
be installed, particularly since the current
version of BS 5534: British Standard for slating
and tiling, was published in 2014 which requires
all tiles to be mechanically fixed.
The Standard provides clear prescriptive advice
on how perimeter tiles should be fixed as well as
minimum fixing recommendations for the whole
roof. Roof tile manufacturers offer site and
building-specific calculated fixing specifications,
most of which can be obtained online instantly.
Despite all this, I am still called upon to
investigate roofs where it is suspected that there
are insufficient tile fixings. The following case
study is based upon actual inspections carried
out on several newly built properties on a single
housing development.
Interestingly, this investigation was
instigated by a homeowner who
saw that the left-hand verge
tiles are secured using visible
verge clips, but the righthand
verge tiles are not –
more on that later.
Fixing specification
The fixing specification issued by the roof tile
manufacturer for this development, has been
calculated in accordance with BS 5534: British
Standard Code of practice for slating and tiling. In
summary, it requires all perimeter tiles to be
nailed and clipped, all tiles in the local areas (a
band of tiles adjacent to the perimeters) to be
nailed and clipped, and all the tiles in the general
roof areas (the tiles in the remaining areas of
roof) to be nailed.
John Mercer, Pitched Roofing Consultant.
The width of local areas is
determined by the width and
length of a building; in this
particular case, the local
areas are a band three tiles
wide adjacent to verges and side
abutments, and four tile courses up
from the eaves and down from the ridge.
Inspection
Rather than lifting every tile on every roof, the
way I approached this investigation was to
inspect several ‘representative’ roof areas.
Whatever I find in these areas is a good indication
of how the roof overall is installed.
Tile fixings
Roof tiles can generally be lifted at their tails
sufficiently to observe the fixings, or lack of them,
under the headlaps. The tiles on this
development, clay single lap tiles, could be lifted
to check the fixings. At eaves, most of the tiles,
though not all, are nailed at the head but not
clipped. Similarly, most tiles in the local areas are
nailed, but not clipped. Not all tiles in the general
areas are nailed and no clips have been fitted.
It was clear, therefore, that the installation of the
roof tiles does not comply with the fixing
specification and, consequently, does not comply
with the requirements of BS 5534.
Verges
To comply with BS 5534, all verge tiles should be
twice fixed. On mortar-bedded verges, this can be
done by nailing and clipping.
Above: This image shows a tile without nails Continued on page 28
26 TC AUGUST 2020