There are a few types of grout which we should talk about. They fall into two main families: cement-based and epoxy-based.



Cement-based grout

Cement-based grount uses common Portland cement as the binding agent. You have two main variants of cement-based grouts: sanded and unsanded grout. The difference is whether or not you have sand in the grout or not. When mixing concrete (for a slab, sidewalk, etc.) you use about 1/3 sand as a filler to bulk up the mass of the concrete and reduce the cost of the area you are trying to fill. So for tiling it is very much the same. The wider the space in your tiling, the more likely you are to need to add sand to your mixture.

I have a rule of thumbs for sand in grout: if it is wider than your two thumbs, add sand!

Because cement is a relatively cheap material, the cost of this type of grout is cheaper ($2-4 per pound) than epoxy-based grout.

Cement-based grout can't generally be stored for more than a year. Once you've bought it, and definitely once you've opened it, you'll need to use it as soon as you can. If it is more than a year old, toss it and buy some more.

Epoxy-base grout

The other type of grout is epoxy-based grout. As with all epoxies it comes in two part that you need to mix together thoroughly. It is harder to work with. It can set up on you part way through a large project (which can be a huge headache) and it can be a chore to clean up. The pluses are that it handles wear really well, and won't crack with age. If you are installing tiles in a high-traffic area, either on the floor or in a public place, epoxy-based grout is probably a good option for you.

Epoxy-based grout is more expensive ($8+ per pound) than cement-based grout.

An added bonus is that properly stored it will last a very long time. Once you buy it, if you don't use it all, you'll have quick access to it in the future.