Slate Floor Tiles

SURFACE PREPARATION FOR CONCRETE FLOORS - Allow new concrete floors to fully cure before tiling (minimum 28 days). If tiling over old concrete remove contaminants by etching with diluted hydrochloric acid. 1:2 with water for really smooth concrete, or a milder dilution for wood floated (slightly rougher) concrete. If tiling over existing tiles etch with a 1:3 solution of hydrochloric. Allow the surface to be etched for at least 15 minutes or until the reaction has stopped (it pays to test a small area first).  Wash the area thoroughly with lots of water and scrub with brush or hard broom to be sure all traces of acid and contaminants are removed. Let the surface dry out before you start  tiling. If you have concrete with structural cracks you will need to repair the cracks before tiling.

SURFACE PREPARATION FOR WOODEN FLOORS - It is ok to tile direct to structurally sound tongue and groove or sound particle board or plywood sheeting providing there is no excess movement. Normally the allowable movement needs to be less that 1/360th of the span between floor joists, or about 1 to 1.5mm maximum.(See below if you have bouncy floors.) Sand down painted floors to remove paint and contaminates and make sure all areas are well nailed or screwed and are clean and dust free. Prime timber floors with a primer or primer/grout additive to ensure a good key to the flooring material. It is important that wet areas are also waterproofed prior to tiling. Timber floors can swell up and lift the tiles and may also rot over a period of time if not waterproofed in areas subject to constant moisture.

If there is excessive movement in the wooden floor is is best to over-sheet the floor with a cement fibre board  prior to tiling. When in doubt use cement fibre board,  it is cheaper to do it right the first time than it is to fix it later. The tile underlay is nailed down around the edges and through the centre to the manufacturers recommendations, normally at 75mm around edges and 100mm through the centre. Most cement fibre boards can be scored with a knife and then snapped to create the required dimensions, which is quicker and easier than cutting it with a saw. After nailing down the fibre board, prime the sheeting and then waterproof  areas subject to moisture or splashes. Allow waterproofing to dry prior to tiling. Always read the instruction on all the products you are using in your project, they will give you invaluable information on the correct use of the material, mixing instructions, approximate coverage etc.  If, having read the instructions, you have any doubts about the suitability of a product for your particular application,  ask your retailer BEFORE you start tiling. It never hurts to double check when in doubt.

SETTING OUT THE TILES - The setting out of the tiles is one of the most important parts of the tiling job. Make sure that you start from the centre and work your way out towards the edges of the room. This will compensate for walls that may not be square, and make the job look more balanced.  Find the centre of the room and then determine where to place the tiles from the centre point that will give you the most even border and the largest pieces when you reach the walls. Try to avoid small  or narrow pieces whenever possible. Before you actually start laying the tiles lay a row out in each direction to help you plan what is going to give you the most attractive look.

A little time spent in the layout will give you a much better end result. If you are laying a border tile first find the centre of each edge and then, either centre a border tile or a grout joint on the centre line  to see which will give you the largest piece or best pattern match when you reach the corner of the room. Often people will lay a 1/4 to 1/2 plain tile around the perimeter and then the patterned border before filling in the central area with plain tiles laid on the diagonal.  It generally looks best to lay tiles diagonally within a border, it also means your border and your tiles do not have to be the same size.  Tiles laid diagonally will generally use approx. 5% more tiles than tiles laid square to the room. In older houses diagonally with a 1/2 tile border may be more in character with your home. In newer homes it will depend on the look you are after. Lay a few tiles out and have a look at which layout you like. Don't forget to allow for the space of the grout joints and a perimeter expansion joint (see below). Normally you would allow 3 to 5mm for inside tiles, 5 to 10mm for outside tiles or even more for very large or irregular tiles. For handmade terracotta, slate or irregular tiles allowing at least 3 to 5  times the variation in the size of the tiles is a good idea. You don't want to have a 3mm joint in one place and nothing in another do you?

As a buying guide work out the nett area then add 10% extra tiles for square laying and 15% extra for diagonal laying. This should give you enough tiles for cutting and some spares. The waste percentage may vary if your room has lots of odd angles or is an unusual shape. - You will want to have some spare tiles at the end of the job for any future repairs.

EXPNASION JOINTS FOR FLOOR TILES - To allow the tiles to expand in the heat make provision for approx. 5mm flexible silicon sealer expansion joint around the perimeter of the job and also every 5 metres through the centre of the work in large areas. If you have an area that gets excessively hot an expansion joint every 3 metres is a good safeguard. Do not lay tiles butted together or hard up to skirting or other materials, expansion joints are a must.

STARTING TO LAY THE FLOOR TILES - After all your preparation is completed, your layout lines are drawn and planning done, you are ready to start laying the tiles.  Use a cement based tile adhesive for concrete floors, a one pack semi-flexible adhesive for over sheeted floors, or floors with underfloor heating, and a fully flexible, two part, adhesive for timber floors, (ask your retailer which is suitable for your job). Mix a small amount of adhesive to begin with following  the manufacturers instructions, you can then mix a bigger amount the next time once you have work out the time it takes you to use it up. Work the adhesive back and forth  into contact with the floor. Then using a notched trowel or notched adhesive spreader, (5mm to 12mm in size depending on the adhesive, tile and substrate), rake the adhesive to form rows of ridges.