Floor Tile Basics: Applying Grout To Floor Tiles

By Bruce W. Maki, Editor

I had never grouted a floor before doing this small tile job. I had only done small repairs. I simply followed the instructions on the bag of grout, and read Setting Tile by Michael Byrne (published by Taunton Press). It is an excellent book that describes everything a person could want to know about floor, wall and countertop tile work.

The first step in grouting the new floor tiles was to remove the plastic spacers. These little X-shaped pieces are made from a soft, flexible plastic, so I discovered that the best way to remove them was to shove my needle-nose pliers into one edge...

... and just yank them out.  I had first tried using a small screwdriver, but that took far longer than pliers.

I vacuumed up the small particles of thin-set mortar that were dislodged.

I applied 2" wide masking tape to the existing marble floor tiles outside the closet.

I used a small part of a bag of colored grout. Note how the second line says "Polymer-modified". This means that an acrylic latex additive has been mixed in already, which will improve the flexibility of the grout once it has hardened.

Grout that is not "polymer-modified" can be enhanced by using an acrylic latex admixture, which is a milky liquid that is used instead of water.

Note that I used "sanded" grout, which contains sand (as a filler) and costs less than "unsanded" grout. Unsanded grout is used where the gaps are very thin and where the tile is soft, such as marble. The sand would probably scratch the polished face of marble tiles.

Using a kitchen spatula I mixed about 4 pounds of grout in a large bucket with water.

This is a grout float. It has a sponge rubber pad on the bottom.

As suggested by the instructions on the bag of grout, I sprayed a light mist of water on the tiles, so they would not rob the grout of moisture and affect its setting.

I slopped a couple of scoops of grout onto the floor, in the back corner.

I spread the grout with the float held at a low angle, about 30 degrees above horizontal. The wiping motion is done at an angle to the grout lines, otherwise the float will catch on a tile edge and dig into the crack.

I carefully spread the grout into all the gaps at the edge of the floor.

After I had gone over the floor once, I continued to push the mortar into the grooves for a few minutes, to ensure that all the grooves were well packed with grout.

Then I tilted the float almost on edge to scrape off the excess grout.

After the scraping was done, the instructions said to wait about 20 minutes before proceeding to the sponge cleaning. So I dumped out the excess grout and cleaned up the tools.

While waiting for the 20 minutes to pass, I used a damp sponge to wipe the grout from the walls.

The sponge cleaning is meant to remove most of the grout from the tiles, but not scoop out the grout from the cracks. If the sponge tends to smear the grout in the cracks, it's too early. If the thin film of grout on the tiles takes a lot of effort to clean, you've waited too long.

The sponge has to be rinsed in a pail of water frequently, and wrung out well. Drops of water on the grout lines may affect how the grout sets.

Since the grout is so close to the tile color, it's hard to photograph the cleaning process. I turned down the brightness on the camera, which seemed to pick up the difference. That darker patch is the cleaned tile area.

The floor after sponge wiping. There is still a haze on the tiles because it is impossible to wipe up all the grout.

After 40 minutes, I used a paper towel to wipe off the haze. The grout was quite firm but could still be scraped up with a fingernail.

The completed tile job. I've turned up the intensity of the colors so you can see the grout lines. It isn't really that bright of a yellow.

I guess the point author Michael Byrne makes is quite visible here. If you want to downplay the geometry of the tiles, use a grout that is close to the tile color. If you want to emphasize the tile geometry, use a grout that contrasts with the tiles

The grout manufacturer recommends that the grout be given a light misting of water a couple of times a day, for 3 days afterward. So I kept the garden sprayer nearby.

Grout is supposed to be sealed after it has fully cured. This is especially important in wet areas. Sealing the grout will make staining less likely, and may deter the growth of mold and mildew.

If you were wondering what those boards on the wall are for... this closet also serves as access to the attic of this old house. I built a set of ladder stairs (behind the wall to the left of the picture), and these are the winders that turn the corner. There is one more step to build, it will sit directly on the tiled floor.

Recommended Reading:

Setting Tile by Michael Byrne, Taunton Press, product #070209 (Available at Home Depot and other stores.)

Copyright © 2001, 2005  HammerZone.com

Written May 16, 2001
Revised January 11, 2005