The key step to installing a successful tile floor or wall finish is choosing the correct thinset and applying it the correct way. Poorly applied mortar will result in tiles not having proper adhesion, which will cause the tiles come loose over time. Poly-modified Thin Set Mortars will always ensure better adhesion, even for ceramic tiles, but are more costly. If using standard un-modified Thin set mortars, the mortar may eventually crack, which will result in tiles coming off prematurely. If you’re on a budget, you can purchase an unfortified adhesive and just add liquid latex to it according to its instructions. Otherwise, you can purchase an already polymer fortified adhesive and just add water to it as directed.
You will need a notched trowel to apply the adhesive. The tile manufacturer will recommend a specific trowel notch size needed for the job. As a general rule of thumb:
- mosaic tile installations up to 2″ square will need a 1/8″ deep notch
- wall and floor tiles up to 4″ square will need a 1/8″ deep notch
- tiles between 4” and 16” square will require a ¼” notch
- tiles between 16″ and 24” square will need a ½” deep notch
- tiles 24″ square and higher will need a ¾” deep notch
If the mortar begins to harden while you are still working on the project, you will need to discard it and mix a fresh batch. The same applies to thinset that has been spread; if it begins to skin over before the tile is placed, it needs to be removed and discarded. Otherwise, your tiles will not adhere properly. Do not apply mortar in direct sunlight or wind-blown areas as this will cause fast drying and poor adhesion.
How to Spread the Thinset
1. Before spreading the mortar, make sure to clean the area and remove all dirt and debris that could cause uneven results. Using warm soapy water, or a mixture of 1 teaspoon trisodium phosphate to 1 gallon of warm water, wipe the area down and let it dry before moving on to the next step.
2. Measure out where you want your tiles to be placed and snap the chalk outline to define tile placement. Do a dry run by placing the tiles along the chalk line markers and ensure that the layout is satisfactory. Make sure to leave room for spacers when you are doing a dry run on your tile placement. Once satisfied remove the tiles and begin.
3. In a 5 gallon bucket, place clean clear water and add the dry thin set mortar and mix the thinset according to the manufacturer’s directions. You can substitute the water with a suitable acrylic additive if needed. This helps to increase the flexibility and bond strength of the mortar. Using a hand-mixer with a paddle, mix the product on slow speed and work the mixture up and down in the bucket while mixing. Mix for at least 3 minutes. Once it is thoroughly mixed,you’ll need to let it rest for about five minutes. Then mix it again before using.
4. Using a trowel, scoop some mortar out of the bucket. Apply the first coat of mortar to the floor at a slight angle with the flat side of the trowel on the surface. Then, using the notched side of the trowel, apply a second coat of mortar immediately following the first.
5. Go back over the area with more pressure this time.You’ll want to hear a scraping sound as the trowel scrapes against the substrate. Apply the thin set in ONE linear direction.This creates grooves needed to allow air to escape after the tile is placed onto the mortar and pressed in.
6. To ensure better adhesion, apply a thin layer of mortar with the flat side of the trowel to the back of the tile before setting it into place. This allows proper adhesion since the mortar gets into the pores of the tile.
7. Set the tile into place on the freshly mortared area and twist it slightly to work it down. Make sure mortar does not seep out over the top of the tiles. If this is occurring, you may need to change the size of the notched trowel for a smaller notch.
Repeat these steps until the project is completed.