January 2020

Perfectly Pitched
long-lasting or heavy enough to wet other
elements or drip onto ceilings, then remedial
action of some kind is required.
Condensation in the roof space may be due to
either a) too much warm air entering the roof
space from the living spaces, b) too little roof
space ventilation, c) overloading of the vapour
permeable underlay, or a combination of all three.
Often, the easiest way to reduce the problem is to
introduce more ventilation into the roof space by
installing tile ventilators. The location of the
ventilators depends on several factors such as
roof geometry and pitch, but as a simple guide, fit
some in the tile courses just above the horizontal
insulation at each side of the roof to aid crossflow
ventilation. Additional ventilators at high level
would act to draw air in through the lower
ventilators.
Roof tile ‘chatter’
Roof tile ‘chatter’ can sometimes occur in high
winds as the tails of the tiles are lifted and
dropped by the wind forces. The sound can be
amplified by forms of roof construction where the
ceiling is fixed directly to the rafters, such as
‘room in roof’ designs.
Tile clips can help to reduce the risk of chatter,
though it is not usually possible to fit clips
retrospectively and their use at the time of the
roof installation would depend on the calculated
wind loading/fixing specification.
Sometimes chatter is restricted to a small area of
roof. Natural or artificial features nearby, or a roof
feature such as a chimney or dormer windows can
affect wind speed or create turbulence causing
uplift in a particular roof area. If such an area can
be identified, then it may be possible to secure the
tile tails in these localised areas by removing an
area of tiling and re-fixing using screws and clips.
The use of adhesive could also be considered,
though this must not be used as a substitute for
incorrectly fixed tiles. Extreme care is needed to
avoid blocking interlocks and water channels and
should be limited to small dabs at the tile tails to
act as ‘cushions’.
“The roof is the primary structure that protects a home” and this offers opportunities for roofers to offer maintenance contracts.
“If efflorescence is to
occur, it usually
happens quite soon
after the tiles are
manufactured and
installed and ceases
just as quickly”
A white bloom on the roof tiles
Although quite rare, a white bloom on concrete
roof tiles is normally a result of efflorescence, a
naturally occurring phenomenon in concrete. As
rainwater wets the tiles, it can draw calcium
hydroxide – which forms during the hydration
process of the cement – to the outer surface of
the concrete. When the tiles dry, a white film – or
bloom – becomes visible on the tile surface. If
efflorescence is to occur, it usually happens quite
soon after the tiles are manufactured and
installed and ceases just as quickly. Then
subsequent rain and general weathering will act
to remove the efflorescence and it will not reoccur.
Sometimes, efflorescence will appear as
streaks emanating from the undersides of the
tiles and running down the tile surface below.
Efflorescence can also occur in mortar bedding at
ridges and hips. Rainwater may wash the salts
down the roof and deposit it on the roof tiles
leaving unsightly streaks. Again, this process
soon stops, and the streaks will eventually
weather away. Of course, the best way to prevent
efflorescence in the mortar is to use dry fix
systems instead of mortar to secure the hip and
ridge tiles.
It is impossible to predict how long the
weathering will take to remove the efflorescence.
There are commercially available liquid
treatments that will remove the efflorescence
faster than natural weathering. A competent
person should carry out the work with full and
safe access and test any product on a small area
first before treating the whole roof.
In summary, the roof is the primary structure that
protects a home, so look after it. As well as
preventing water ingress and wind damage, home
insurance policies are normally only valid so long
as the property is properly maintained.
Contact Edilians / John Mercer
www.imerys-roof-tiles.com
@imerys
@johnmercer3
30 TC JANUARY 2020