If you want to replace an old floor, you might think that the only possibility is to carefully remove the old tiles. However, if the existing flooring is in good condition, you can lay the new tiles over the old ones. However, this procedure requires specific preparation, a little longer than normal.
Steps
Part 1 of 3: Prepare the Surface
Step 1. Check that there are no moving tiles
Tap each old tile with a wooden hammer. If the sound is full, the tile is fine. If it seems to you that it is empty below, it means that the tile is unstable and the problem must be solved.
- Break up the old putty or putty around the tile and lift it up using a crowbar. Be very careful to avoid damaging it.
- Prepare some cement adhesive (mortar) according to the instructions on the package and spread it on the back of the old tile. Then put it back in its place.
- If you need to fix some wobbly tiles, wait 24 hours to allow the grout to dry before proceeding to the next steps.
Step 2. Mark any bumps or bumps
Using a 1.5m level, look for particularly high or low spots on the tiled surface.
- Mark these points with chalk. Use different symbols to tell them apart. For example, you could use a "B" or a dash for a point lower than the surface and an "A" or a triangle for a point higher.
- Make sure all four corners of the bump or gutter are marked.
Step 3. Smooth out any bumps
Use an angle grinder with a masonry disc to scrape off the raised spots on the old tiles.
- Check frequently with the spirit level that the point is even with the rest of the surface.
- At this stage you are only fixing the bumps. We will deal with the bumps later.
Step 4. Scratch the rest of the tile
Sand the entire surface of the tile using a belt sander or an orbital sander with 80-grit sandpaper.
- Make sure any enamel or surface finish has been thoroughly sanded.
- A rough surface has more grooves that the grout can enter, thus making it adhere better to the surface itself. For this reason, sanding the surface of the old tiles will help the new ones to sit better in place.
- If you don't have a sander available, you can sand the tiles using steel wool.
Step 5. Remove the damaged grout
You will be able to keep most of the old grout, but you should remove any moldy or crumbling grout using a rotary tool or tungsten carbide scraper.
Step 6. Clean the surface
Vacuum the old tiles using a powerful vacuum cleaner, then scrub the surface with detergent and hot water to remove any other dirt and debris.
- The detergent must be able to degrease the ceramic surfaces.
- Rinse the old tiles with clean water and dry with a rag or towel. Let the remaining moisture evaporate for a couple of hours.
Part 2 of 3: Laying the New Tiles
Step 1. Apply a layer of cement adhesive to the floor
Mix the mortar with elasticizing latex and spread a thick, even layer of compound onto the work surface using a notched trowel.
- As a general rule, it is best to work from time to time on small portions of the floor, portions that you think you can complete in half an hour or so. If you prepare too much mortar, it may start to dry out on the surface and be less effective.
- Apply the adhesive in one direction only. Don't spread it around. Small grooves should form in the mortar.
- If there is a crack in the old flooring, it may be necessary to use a little more mortar than normal to fill the crack.
- The thickness of the adhesive should be about 6.5 mm.
- You could use powdered mortar to mix with a liquid admixture based on latex, rather than with water.
Step 2. If necessary, give more stability by using mesh tape
When you are laying the tiles on a cracked surface, you should embed a strip of mesh tape in the fresh grout above the crack. Use only enough tape to cover the gap.
The tape will serve to give stability to the mortar. This makes it less likely that the crack on the underlying surface will reappear on new tiles
Step 3. Apply the adhesive to each tile
Prepare the necessary mortar and spread a thin, even layer of adhesive on the back of each tile using a notched trowel. Make sure you cover the entire surface of the tile.
- As before, it's best to work with the amount of tile you plan to lay in about 30 minutes.
- Apply the mortar in one direction only, making small grooves with the notched trowel.
- The thickness of the adhesive on the back of the tile should be no more than 6.5 mm, if not a little less.
Step 4. Lay the tile
Slide the tile into place, placing it according to the pattern you have established for the floor. Spreads of adhesive on the surface should be perpendicular to the grooves on the back of the tiles.
You must start laying from the center of the work surface and move towards the outer perimeter, just like you would for a surface that has not yet been tiled
Step 5. Add cement adhesive to even out any bumps
When you reach points that you have marked lower than the rest of the surface, apply more mortar to the back of the tile that you will be laying there, so that it is on the same level as the others.
Check with a spirit level that the tile is level with the adjacent tiles. Since the mortar dries slowly, you can still remove the tile that has just been laid and add (or remove) some adhesive, in case you were unable to obtain a flat surface on the first attempt
Part 3 of 3: Adding the Final Touches
Step 1. Let it dry for 24 hours
Before doing anything else on the newly tiled surface, you must let the adhesive dry for at least 24 hours.
- In any case, you can clean the still wet mortar residues from the tiles even before this period has elapsed using a wet rag. However, this procedure is recommended, because dry mortar is more difficult to remove.
- Once dry, gently tap each tile with a wooden hammer to make sure they are all secure. As before, you can spot the rickety tiles by listening to the sound - if it's deaf, something is wrong. At this point there should be no unstable tiles, but if this happens, remove the tile in question and spread more mortar on the back. Put the tile back in place and let it dry for another 24 hours.
Step 2. Grout the joints between the tiles
Prepare the grout as indicated in the instructions and place it between the joints to seal the tiles together. Fill the joints well using a putty knife.
- Use a sandblasted grout if you are laying the tiles on a floor, and a non-sandblasted one if you are covering a wall instead.
- Let the grout dry for at least 3 days.
- Once dry, you could seal and protect it by applying a silicone-based sealant.
Step 3. Clean the surface again
Once the grout has dried, remove any residue from the tiles using hot water and detergent.
- This will help you bring out the beauty of your new tiled surface.
- With this last step you will have completed the work.
Advice
- Before starting to work, remove all the elements that will have to be placed on top of the tiles.
- To make sure you have a flat bottom, you can draw a grid on the surface using chalk, after you have prepared it and before you start laying the tiles.
- If you need to cut tiles, use a water-based tile cutter.
Warnings
- While working, wear safety glasses, a dust mask, and sturdy work gloves (leather or rubber).
- You can install new tiles over old ones only if the underlying floor is compact, concrete or mortar. If this is not the case, you will have to remove the old tiles and redo everything from the beginning. You will find that the floor is not consistent if it shifts or moves when you walk on it.
- Watch out for cracks in old tiles. Often these cracks indicate a problem in the underlying concrete layer. While you can lay new tiles on these cracks, it's better to fix the root problem instead of just covering it up.
- The new surface will be a little higher than the old one. Keep this in mind if you need to place elements on a freshly tiled wall or floor.
- It may be necessary to cut the door frame or bottom if the threshold of the new floor is too high to prevent it from closing.
