Surface Preparation

Surface Preparation - Every Floor Is Different

Always keep in mind that no two surfaces are the same. Each surface has its own characteristics (such as rate of expansion and contraction, moisture absorption, 'dimensional stability,' and so on). It pays to know the nature of each surface as these characteristics must be considered when choosing the right adhesive for the job.

You may see the word ‘substrate’ used in manufacturers instructions. This is the main underlying surface the tiles will be applied. Regardless of the surface type, all surfaces must be structurally sound and strong enough to support tiles as well as clean, dry, and free from all dust, dirt or contaminants and any existing surface coatings such as polish, lacquers, sealers, or paints.

All surfaces should be flat. Interior floors should have a maximum of 5mm variation across 3 metres whereas an exterior floor or balcony should be no more than 10mm of variation in 3 metres. Where floor surfaces are not flat, a levelling compound may need to be applied before tiling.

Compressed Fibre Cement Sheets

Compressed fibre cement sheets are dense flat sheets of reinforced cement, and should be fixed according to the manufacturer's instructions. Ensure that the surface is clean and dry.

Compressed Fibre Cement Sheet to be used as a substrate for a floor tiling should have a minimum thickness of 15mm and a minimum thickness of 9mm for wall tiling to comply with Australian Standards.

Most fibre cement sheets have a surface layer of dust which should be removed by using a damp sponge or cloth before priming and tiling. Before tiling, prime all compressed fibre cement sheets with a compatible primer with the tile adhesive. Ask your Beaumont store for their recommended primer and fibre cement sheet joint covering products.

Because timber naturally expands and contracts, we don't recommend adhering tiles directly onto timber floors. Untreated floors should be primed and allowed to dry before tiling. We recommend you install an underlay of fibre cement sheet over the timber and prime it before tiling. The minimum thickness for compressed fibre cement sheet as an underlay is 6mm.

You can lay tiles over structural particleboard such as STRUCTAflor YELLOWtongue but there are particular materials to use and steps to follow. Check with your team of experts at your local Beaumont Tiles store for their recommendations.

Ceramic tiles can be laid over virtually any level, firm, rigid surface that is clean, dry and structurally able to support the weight of the tiles; e.g. plaster, cement render, fibre cement sheet, plasterboard. Even surfaces like metal, old tiles and wood can be tiled over using the correct adhesive although it is not advisable to tile over fibreglass.

If you plan to tile over plaster or cement render, patch any small irregularities with one of the many excellent fillers available for this purpose. If the wall is really rough, it will probably be worth lining it with fibre cement sheeting. To do this, simply plug and screw 45mmx19mm battens to the wall at intervals recommended by the fibre cement sheet manufacturer. Make sure that each batten is vertical and level by packing behind the batten until your spirit level shows it is just right. Then, simply fix the fibre cement sheet following the manufacturer’s instructions and prime the surface.

If the existing tiles are glazed, roughen the surface with mechanical means like a grinder, removing 90% of the glaze before tiling over them. Alternatively, you can also use a specialised primer to etch the tile surface. Don’t forget to wear appropriate safety equipment including gloves, hearing and eye protection along with a well-fitted mask or respirator to avoid breathing harmful dust when using a grinder. Once this is done and the patching mortar has dried, thoroughly vacuum the area to ensure it is free of loose material and dust, then scrub the floor clean with tile and grout cleaner to remove oily residues, paying particular attention to grout lines. 

Are There Any Drawbacks To Tiling On Tiles?

The main drawback to tiling on existing tiles is the extra layer of thickness or added height you’ll end up with, particularly with your floor tiles. By effectively adding a second layer of tiles over another one, your floor will end up several millimetres higher. Any additional floor thickness may not be an issue as long as you measure carefully and trim the bottoms of any doors that open into the area and ensure you do not create a trip hazard.

There are some thinner tiles available that can reduce the overall thickness when tiling on top of tiles, especially for walls. 

When removing old tiles, always wear long-sleeved clothing, safety glasses, gloves and an appropriate dust mask/respirator as breaking up old tiling can create a lot of dust and sharp shards of tile.

Cover the surrounding area with a strong plastic drop sheet and have a rubbish bin on hand for tile pieces. The tools you will need are a hammer, cold chisel, flat pry bar, and a flat scraper. 

Very old tiles may have been installed on a bed of cement mortar over reinforcing wire. It is more common, however, to find tiles installed with adhesive onto fibre cement sheets or plasterboard.

First, remove any skirtings and any fittings from the tiles. Carefully cut through any silicone perimeter joints on the tile area you are removing so you do not damage the surrounding surface areas.

It may be possible to remove complete tiles, depending on the type of adhesive originally used. If possible, find an exposed edge of the tiling. Try inserting the flat scraper between the back of the tile and the substrate, using a hammer if necessary. If the tile comes away easily or relatively cleanly, you may be fortunate and not have to replace the substrate. If there is only minimal damage to the plasterboard or cement sheet surface, scrape off all residual adhesive and patch any holes or gouges with patching plaster or patching cement to give a clean, smooth and flat surface to tile onto. Remember, you'll need to seal any newly patched areas and substrate before tiling. 

If there is no exposed tiling edge, use a sharp edge to remove the grout around a tile and a hammer and chisel to break up the tile. Try to slide a scraper or pry bar underneath an adjoining tile and attempt to pry the tile loose. If the tile does not budge, you will most likely have to break up the tiles with the hammer and cold chisel.

If the tile breaks away in lumps with pieces of the substrate still stuck to the back, it will be easier to cut around the edge of the tiling and break up the wall section and remove the underlying substrate of plasterboard or compressed cement sheet from the wall studs in larger pieces with the tiles still attached. The exposed wall studs can then be re-sheeted with new compressed cement sheeting, ready to be primed and accept new tiles. 

Gradients In Wet Areas

The main consideration in the National Construction Code and the relevant Australian Standards for a wet area floor is that all surface water does not remain or pond on the floor but drains away.

The standards that cover the gradient falls required in showers and wet areas include Australian Standard AS3958-2023 for tiling, AS 3740-2021 for waterproofing and the National Construction Code (NCC), formerly known as the Building Code of Australia. There are some variations and higher requirements in certain states regarding the required gradient falls in wet area floors so it is best to discuss with a builder and familiarise yourself with these. 

For all internal wet areas and general bathroom floor areas, the recommended gradient fall towards the waste is a minimum of 1:50 and a maximum of 1:80 (between 12.5mm - 20mm for every 1 metre of distance from the waste inlet). 

This is the same for the shower floor area where the gradient fall should be sufficient enough to prevent water from being retained on the shower floor or discharging outside the shower area, even if the shower area is separated  by a shower screen, hob, step down, or water stop.

For external areas, the gradient fall should be a minimum of 1:100 (10mm for every 1 metre of distance).

Tiles may require diagonal cutting in the area around the waste to achieve the required gradient and sufficient drainage. With many modern bathrooms now featuring large format floor tiles, incorporating a linear drain in the shower area can make achieving the gradient easier and avoid the need to cut tiles to achieve the required drainage. 

You may ask “How do you get the water to end up where you want it”? The answer is to start with the drain or grate. This will include the main shower and any floor drain required outside the shower area. All levels should be taken from there and worked outwards. The floor gradients can be achieved by laying a cement screed onto a suitably prepared substrate. Screeding a floor and setting levels for the required falls is not something for a first-time DIY tiler.