5
Substrates
If your tiling is to last, it is essential that
the surface onto which the tiles are to be
laid is sound. Careful consideration must be
given to the floor surface to confirm that
the surface is level, clean, dry, free of dust,
grease and any loose material.
Your tiler must confirm the suitability of
the subfloor before tiling.
Sand and cement screeds
When tiling onto a new screed, a minimum
period of one week for each 25mm of new
screed should elapse to allow the screed to
be suitably dry. Further time may be
necessary, depending on weather and site
conditions. We do not recommend tiling
onto anhydrite or fast setting screeds
without careful consideration - please
contact our Technical Department for
further advice.
A new screed may shrink as it dries, and
this may result in cracks across the screed.
If cracking does occur it is likely to appear
across any tiles that are fixed to the screed.
Ensure that the screed is suitably dry and
stable before any tiling is started.
Any movement or day joints in the screed
must be carried through into the tiled
surface. Day joints or construction joints
must not be tiled over without the
inclusion of an expansion joint.
Bumps and hollows
in screeded floors
Minor irregularities can be overcome with
up to 5mm of
Fired Earth Universal
Levelling Compound*
or
Fired Earth Thick
Bed Adhesive*.
If the floor is very uneven,
with undulations of more than 5mm,
Fired
Earth Universal Levelling Compound*
should be used in conjunction with clean
granite chippings.
Suspended timber floors/
Floating insulated floors
Suspended timber floors/floating insulated
floors (polystyrene with water resistant
chip board over) should be rigid, non-
flexing and stable enough to bear the
additional load. In order to minimise the
damaging effect of lateral movement in the
floor surface, it is recommended that the
floor is prepared using
Fired Earth
Fleximat*
. Our Sales Team will be happy to
provide our separate information sheet.
If the suspended timber floor is subject to
vertical movement, the floor must be
stiffened. Remove flexing by fixing a
minimum 18mm, WBP plywood over the
existing timber, screwed down at 150mm
centres. If the floating insulted floor is
subject to vertical movement the floor
must be braced by screwing and gluing
WPB plywood to its surface, or removing
4
some of the boards so 'bearers' can be
fitted below to provide further support.
Seal all the surfaces of the plywood boards
with
Fired Earth Universal Bonding Agent*
Other types of floors
Fired Earth would recommend that all
existing floor covering and residue adhesive
are removed before tiling. However it is
possible to tile over existing tiles provided
the surface is completely sound, secure and
thoroughly cleaned to remove all
contaminants such as oil, wax and grease,
using an appropriate cleaner.
Cork and woodblock floors must be
removed and any bitumen left on the
subfloor should be scraped away and all
loose material removed.
Vinyl tiles must be primed with
Fired Earth
Universal Bonding Agent*.
Damp
Prior to fixing tiles, damp of any nature
should be rectified. Consult a specialist if
any doubt exists.
Finished floor level
The finished level of an existing floor will
be raised by the maximum thickness of the
tile plus approximately 3–4mm adhesive
bed. Any resultant discrepancy with the
levels of adjoining rooms can be minimised
with the use of threshold/reducer strips.
Underfloor heating
Fired Earth floor tiles can be used over most
underfloor heating systems. The heating
should be correctly commissioned prior to
tiling and switched off during tiling. There
must be no cracks in the screed otherwise
any floor tiles fitted on top will crack.
Fired Earth Fleximat*
can be used as an
anti-fracture membrane over Fired Earth
Underfloor Heating. Our Sales Team will
be happy to provide our separate
information sheet.
Always use flexible adhesive and grout and
provide an expansion gap around all
perimeters and abutments. As a general
guide, do not tile continuously over areas
with a length of over 6 metres, fit an
expansion gap to prevent stress building up
in the floor. Always fit expansion joints in
doorways of adjoining tiled rooms.
DO NOT switch the heating on for at least
two weeks after tiling, then, starting from
ambient temperature, do not increase the
temperature by more than 5°C in a 24
hour period until the normal working
temperature is reached.
'Wet' floors
Please refer to our
Waterproofing Showers
and Bathrooms Installation Guide
for
further advice.
Walls
When tiling onto walls with floor tiles,
consideration must be given to the weight
of the tile and suitability of the substrate.
Our Sales Team will be happy to confirm the
weight of any of our tiles.
