Why Dot and Dab Tiling Should Be Avoided
DISCLAIMER - This is a guide only and Tilesporcelain Ltd is not liable for the finished tiling project.
You may have heard the term ‘dot and dab’ in relation to fixing tiles onto a surface with adhesive. In dot and dab tiling, adhesive is applied on only sections of the surface area and the back of the tile opposed to an even layer, which is the traditional method. The dot and dab technique results in the back of the tiles and surface upon which they are laid on not being completely covered in adhesive. Instead there will be gaps where the tile is not secured by any form of mortar which can cause many short term and long term problems. Below we explain why the dot and dab method should be avoided.
First of all because the tiles are not properly secured, some may even fall off walls before the adhesive has set thus potentially causing damage to the floor or application below or even worse harming yourself or somebody else in the room. Although floor tiles applied in this way will pose less risk to yourself and others it is still not recommended.
Moisture damage can be a big problem with tiles that have been applied through the dot and dab method. Even waterproof adhesive cannot compensate for gaps where the area between the back of the tile and underlying surface is not filled. Moisture can cause mould and dampness which over time will not only cause damage to the underlying surface but may also result in the tiles becoming loose. Moisture can also penetrate through to the surface of the tiles, causing permanent staining.
Dot and dab tiling does not provide a secure fix on floors. Areas beneath the tile which are not covered with a layer of adhesive will be weaker and therefore more likely to crack under pressure.
The dot and dab method actually goes against the British Standard code of practice for tiling. Here is a recommended way of fixing tiles with adhesive which complies with British Standard guidelines: Begin by spreading an even layer of adhesive across a small section of the substrate with a trowel. Working in small sections will ensure the adhesive will not begin to set before you fix the tiles in place. Butter the back of the tile with adhesive before pressing and twisting into place. This method will ensure there are no gaps between the back the tile and the underlying surface. Correctly fixed tiles can last a very long time providing they are properly maintained.
Within the Code of Practice BS 8000 Part 11 and BS 5385 Parts 1 to 5 you will discover recommendations on tiling best practice. BS 5385 highlights the necessity for solid bedding regardless of whether the tiles are being installed on a wall or floor.
BS 5385 part 1 was revised and published in June 2018 and clearly states that: “Tiles should not be fixed using the dot and dab technique.” This can be found in item 18.104.22.168. Item 6.3.1 of this section also provides guidance in relation to the installation of tiles: “Tiles with a surface area of less than 0.1 m2, but which weigh more per square metre than 70% of the background’s capacity to carry the weight, should be solidly bedded e.g. the maximum weight of tile that can be supported by Gypsum plaster = 20kg; whereas 9mm thick porcelain tiles, which weigh approximately 18kg/m2, weigh more than 70% of 20kg (14kg) therefore, they should be solidly bedded regardless of their size.”
There is further reference to the correct bedding method for the installation of tiles within item 22.214.171.124 which states: “Tiles can be bedded directly to a background using an appropriate adhesive as the bed. Methods of application and suitability of backgrounds to accept these methods are described in Clause 7 and Table 3. The surface should be true such that, when checked with a 2m straightedge with 3mm thick feet at each end, the straight edge should not be obstructed by the background and no gap should be greater than 6mm.”
Further recommendations are found in BS 5385 Part 3:2014 which concentrates on the Design and Installation of Internal and External Ceramic and Mosaic Floor Tiling in Normal Conditions. You will find this information in Section 7 Clause 126.96.36.199.1 in reference to the notched trowelling and Buttering technique: “When floor tiles are fixed using normal cementitious adhesives, the adhesive should be applied to the sub-floor as well as to the back of the tile to ensure solid bed fixing. The mixed adhesive should be applied to the sub-floor using a trowel as a floated coat, pressing the adhesive into the surface before combing through with a notched trowel as a spreading gauge to provide a uniform ribbed adhesive bed. The backs of the dry tiles should be buttered with the adhesive to coat the surface and to fill flush any back profile or key to form a contact layer before placing the tile on the ribbed adhesive bed. Each tile should then be pressed or tapped down firmly into position with a rubber mallet. The adhesive should preferably be trowelled out as straight ribs and tiles should be pressed into the ribbed adhesive bed whilst the ribs are still wet and workable, i.e. within the “open time” of the spread adhesive.”