Floor tile grout is the compound which is used to seal the gaps between laid tiles to ensure that the flooring is waterproof. If two tiles were butted directly next to each other no matter how tightly, there would always be a fine gap where water could seep through. By widening the gap though and filling it with wet grout mixture, the floor tiles are then appropriately sealed against the introduction of water. Grout is normally bought in a dry powdered format, and mixed with water to form an applicable paste substance.
Although there may be a multitude of grout colors and brands available on the market, there are predominantly two different kinds of grout. These are sanded and non-sanded grouts, and the brand which I particularly like to work with is Mapei. Sanded grout is basically a cement powder with the addition of fine polymer silicon particles which give it that slight grainy texture when mixed. This is suitable for the majority of tiling applications, except for grout lines of 1/8″ inch and less or for wall tiling applications.
For these purposes you will need to use non-sanded grout, which basically dries to a more compacted compound and will apply easily to narrow grout lines when doing marble or granite floor tiles for example. Sanded grout particles will also tend to scratch these glass-like tiles, so should never be used whatever the case. When doing wall tiling also, non-sanded grout is ideal because it tends to sag less than sanded grout when working where gravity is your enemy for once.
Once your grout has been applied, you then need to seal it with the appropriate grout sealer. Again there are many brands available of which I prefer to use the mid-range Aqua Mix products which are good price and quality, but there are two different types of grout sealant found. These are known as high and low sheen finishes, and are relevant to how much of a gloss you wish to maintain on both your grout lines and floor tiles where applicable.
Sealing grout lines and floor tiles should be done periodically depending on the manufacturer’s instructions, in order for the tiled floor to maintain its waterproof qualities. There is however some more expensive brands of grout sealer available which claim that only one application will do the job for years to come. These I have honestly yet to try and can’t really agree with what they claim, but to be safe and keep costs low, try to stick with the mid-range sealants and be prepared to undertake a simple annual sealing of your tiled floors.