Dry, smooth and flat concrete floors are suitable for any kind of tiling.
If the floor is very uneven - differences in depth greater
than 12mm, use a sand and cement screed of at least 12mm
thick. Use a coat of proprietary sealer on the uneven surface
before laying the screed, especially if the original surface
is dusty. Leave the floor for approximately four weeks before
commencing tiling. Tiles can then be laid directly onto
the screed.
A water-based levelling compound is suitable for levelling
a concrete floor, if the depth is less than 12mm. It comes
in powder form and is mixed to a paste and then a thin layer
- no more than 4mm (3/16 inches), spread over the floor.
Before beginning, repair any cracks deeper than about 3mm
(1/8 inches) by cleaning the cracks and removing any
loose debris - with a hammer and chisel if necessary. Apply
PVA adhesive and then fill the cracks with a sand and cement
mortar. Deeper cracks (10mm) should be cleaned, and using
a bonding agent filled with sand/cement using a 3/1 mix.
Allow the area to dry and make sure the floor is clean before
applying the levelling compound. Use a wire brush to clear
out any cracks or corners and remove any oil or grease by
washing the entire surface with detergent.
Mix up the compound, following the manufacturer's instructions
- it should be free of lumps and have a creamy consistency.
Start in a corner of the room furthest from the door and
trowel, using a steel float outwards to an even thickness
of approximately 3mm (1/8 inches). Keep the level horizontally
even, but it is unnecessary trying to smooth over any marks
from the surface, as the compound will seek its own level.
Continue across the room until the entire floor is covered.
When the floor is hard enough to walk over, smooth out
any small lumps with a little water and the steel float.
Although it is safe to walk on the surface after an hour
or so, the covering should wait for a few days to allow
the compound to harden.
