Tiling onto Masonry
In general masonry can provide a good background onto which tiles can be applied,
though differences are found between existing and new masonry construction.
Unfortunately, however, the specification for masonry construction does not
necessarily provide a suitably flat surface onto which tiles can be applied. In these
instances it will be necessary to cover the masonry with a cement sand render or
plaster onto which the tiling can be applied.
Existing brick/blockwork walls
There are three basic classes of masonry units, as listed below:
Dense, strong and smooth surfaces materials. These materials (which include
high-density clay bricks or blocks, dense concrete either pre-cast or in-situ, some
natural stones, glazed brick and some glazed tiles) have low porosity, little suction
and smooth surfaces that offer no mechanical key. Very little shrinkage will occur with
such materials.
Moderately strong and porous materials. Most bricks and blocks fall into this category;
they have moderately high suction and usually provide a good mechanical key onto
which to tile.
Moderately weak and porous materials. Blocks made of lightweight aggregates,
autoclave aerated concrete and some bricks of low density may be too weak to
provide a suitable base onto which tiles can be applied. Such materials should not be
used as a background for rendering prior to tiling unless a reinforced wire mesh is
incorporated into the render to make the material essentially self-supporting.
Preparation
As the masonry is not new no particular drying period should be required. If however,
the masonry has suffered from rising damp and no DPM is present it may be
advisable to have a chemical DPM injected into the masonry prior to tiling. Where
water can build up along a construction interface there is always a possibility of failure
and this should be minimised whenever possible.
The masonry should be sound, clean and free from loose deposits of dirt, dust, and
mortar. If the surface of the masonry is poor, the affixing of ceramic tiles may result in
a failure along this interface. Where surfaces appear to have moderate to high suction
priming is required.
Multiprime should be used and applied using a brush. Coverage will depend on
porosity and regularity of the surface. The drying period would be best judged on site,
and will also depend on the ambient temperature and humidity.
Adhesives
For dense blocks and low suction i.e. engineering, bricks Superglue or Megalastic
fortified Fixall or Superfixall should be used. When using white grouts, light toned
marble or natural stone tiles a white adhesive such as Superfixall White should be
used.
For moderate masonry units any cementitious adhesive is suitable. For external
applications use Fixall or Superfixall.
Grouting
Grouting may commence once the adhesive bed has firmed up. We would
recommend the use of a polymer-modified grout, such as Bostik Coloured Grout or
Bostik Sanded Grout. Drying will vary according to the site and ambient conditions.
Movement Joints
Any movement joints visible should be followed through the tiling to the surface.
Failure to do this may result in excessive movements within the structure being
transferred to the tiles with the likelihood of resultant failure of the system.
New brick/blockwork walls
Preparation
With reference to the above, it must be concluded that new masonry is subject to the
highest risk factor with regard to shrinkage and the consequences thereof. Ideally,
masonry should be left for at least 6 weeks after construction, for the materials to
stabilise to the ambient conditions after rendering, prior to any commencement of
tiling.
Where surfaces appear to have moderate to high suction, priming is required.
Multiprime should be used and applied using a brush. Coverage will depend on
porosity and regularity of the surface. The drying period would be best judged on site,
and will also depend on the ambient temperature and humidity.
Adhesives
For dense blocks and low suction, i.e. engineering, bricks Superglue or Megalastic
fortified Fixall or Superfixall should be used. When using white grouts, light toned
marble or natural stone tiles a white adhesive should be used.
For moderate masonry units any cementitious adhesive is suitable. For external
applications use Fixall or Superfixall.
Grouting
Grouting may commence once the adhesive bed has firmed up. We would
recommend the use of a polymer-modified grout, such as Bostik Coloured Grout or
Bostik Sanded Grout. Drying will vary according to the site and ambient conditions.
Movement Joints
Any movement joints visible in the screed should be followed through the tiling to the
surface. Failure to do this may result in excessive movements within the structure
being transferred to the tiles with the likelihood of resultant failure of the system.