I recently received an e-mail from a reader asking about painting over terrazzo floors; since so many homes built during the 40's and 50's had this material, I thought that it would make a good topic.

Antoine,
Terrazzo floors are becoming a hot, retro, design element, and can be cleaned and buffed into a design asset. However, if you have your heart set on painting the terrazzo:
Yes. It is possible to paint over terrazzo floors, provided that you properly prep the floors, first.
Many times terrazzo floors were covered in the 60's and 70's with carpet or vinyl tile. It is very important that you remove any traces of adhesive and/or foam padding that might have stuck to the floor. You can do this by using a 2"-3" heavy bladed scraper and a solvent cleaner, like "Goo Gone" or "Goof-off".
The next step is to thoroughly clean the floor, to remove any grease, oil or dirt. A product that I find very effective is TSP, or Tri-Sodium Phosphate, available as either a powder, or a concentrated liquid. Mix this according to the directions on the packaging, apply to the floor, and using a mop or large sponge, clean the floor. Rinse with clean water, and let dry for a day before proceeding.
You now need to apply a good, bonding primer; I like UMA, a really strong white latex primer that is sold through retail paint stores (not Home Depot, or Lowe's). Roll on a light coat of the primer over the whole surface, and let dry.
Two things: It is not necessary to apply a solid coat of primer; it is, in fact, a waste of material. A thin coating is all that is needed.
Second, for a primer to reach maximum bonding capability, it must "cure", or harden for several days. The UMA works best if you give it 3-5 days to cure before top coating. Now, the UMA dries to the touch, and can be walked on, in a couple of hours; just be careful not to track any dirt on it while it cures.
You can now paint the floor with any good quality, water based floor paint. Many of these paints are tintable, so it is possible to create a faux finish, using just about any technique that you want.
You can then clear coat the floor with a good, clear acrylic finish, like Benj. Moore's Stays Clear Low Luster Acrylic Finish.
Hope that helps. Good luck, and best wishes,
Glenwood
That Paint Guy