Masonry is generally a good foundation for applying tiles although there will be variations according to how old and in what state the brickwork is found. If the brickwork is uneven it may be necessary to create a flat surface with plaster or a sand cement render, such as PCI’s Polycret 5 (see guidance notes on gypsum plaster on page XX and sand cement render). There will also be variations depending upon the type of masonry.There are three general types:
High-density clay bricks, dense concrete, glazed brick and some glazed tiles and natural stones - these provide a dense, strong and smooth surface with a low porosity.While very little shrinkage will occur with such materials, they provide minimal suction and their smooth surfaces offer no mechanical key.
Most bricks and blocks - they are porous and quite strong with a moderately high suction and a good mechanical key.
Lightweight aggregate blocks, autoclave aerated concrete and some low-density bricks - these are generally too weak and porous to support any type of tiling application. The only exception is when a self-supporting reinforced wire mesh render is placed on top of these materials.
Existing masonry walls Preparation technique
Check that this existing masonry has a DPC (Damp Proof Course). If one isn’t present, a chemical DPM can be injected into the masonry.
Where water can build up along a construction interface there is always a possibility of failure and this should be minimised whenever possible.
Make sure that the masonry is clean (free from dust, dirt, dust, grease and residual adhesives) and of sound construction.
Prime the surfaces which have a medium to high suction rate. Use a primer, such as PCI’s Primer G (dilute 1:1,water:Primer G).
Adhesive application
For dense blocks with low suction use PCI’s Tilefast 6 Flex Thin or Thick Bed Adhesive
For standard bricks and blocks, any cementitious adhesive is suitable such as PCI’s Tilefast 6.
For external applications use PCI’s Tilefast 6 Rapidflex.
When using a white grout, always use a white adhesive.
For light toned marble or natural stone tiles use a specialist adhesive, such as those from PCI’s Carra range, so as to avoid any discolouration.
When using porcelain or vitrified tiles, use PCI’s Tilefast 6 Rapidflex to promote bond strength.
Grouting
-
Once the adhesive bed has firmed up, grouting may commence.
-
A polymer-modified grout is ideal for masonry, such as PCI’s Groutfast 20 Rapidflex or Groutfast 8 plus and admix.
-
Drying time will depend on the site conditions and type of tiles.
Movement Joints
Please refer to Special Situations Bulletin 1 due to the complexity of this subject.
New masonry walls Preparation technique
-
New masonry walls are subject to shrinkage (please refer to the Special Situations 3:Masonry - shrinkage and movement).
-
After construction, and before tiling, allow at least 6 weeks for the background materials to sufficiently dry out.
-
Prime existing surfaces with high suction. Use a product such as PCI’s Primer G (dilute to 1:1,water: Primer G).
Adhesives
-
For dense blocks with low suction use PCI’s Tilefast 6 Flex Thin and Thick Bed Adhesive.
-
For standard bricks and blocks any cementitious adhesive is suitable such as PCI’s Tilefast 6.
-
For external applications use PCI’s Tilefast 6 Rapidflex.
-
When using a white grout, always use a white adhesive.
-
For light toned marble or natural stone tiles use a specialist adhesive, such as those from PCI’s Carra range, so as to avoid any discolouration.
-
When using porcelain or vitrified tiles, use PCI’s Tilefast 6 Rapidflex to promote bond strength.
Grouting
-
Once the adhesive bed has firmed up, grouting may commence.
-
A polymer-modified grout is ideal for masonry, such as PCI’s Groutfast 20 Rapidflex.
-
Drying time will depend on the site conditions.
Movement Joints
Please refer to Special Situations Bulletin 1 due to the complexity of this subject.