How much do these floors cost?
$1.50-$25/sf. More than 80% of the floors we make are around $4/sf. They tend to be new construction projects working through builders or architects and even after their mark-up it's surprisingly inexpensive.
Aren't those shiny floors slippery?
Some are, some are not, and here's why:
Our diamond polished floors can be extremely shiny, but since there is no plastic sealer on the top they are surprisingly slip-resistant when wet. Regular dust-mopping is required to keep them as safe as possible.
Floors coated with acrylic, urethane or some other plastic (not how we generally do it) are slippery when wet unless grit is added to the top-coat. Gritty and pretty are inversely related: the more gritty the less pretty (in general). Coated floors are very chemical resistant so we do occasionally install coatings.
What is an overlay?
An overlay is a good solution to concrete that cannot be ground and polished into something sufficiently attractive. They can be resinous or cement-based. Regardless of what the makers of these materials claim, none of the cement-based overlays are as hard/durable as real concrete. We say that humbly: nobody wishes these materials were truly great more than us.
That said, we have devised a process for interior overlays that is not cheap, but often worth doing. We figured out how to diamond polish troweled-down polymer-modified mortars rather than using self-leveling materials that are designed to be polished. That is because those self-leveling materials are gorgeous when first installed, but tend to crack up badly over the years. At more the $10/sf, we would not want to be on the other end of that deal, so we do not generally install those.
What is diamond polishing and why bother with it?
Diamond polishing is finishing concrete by "sanding" it with progressively finer abrasives made of diamonds impregnated in metal or resin. The alternative is finishing concrete by coating or forming a film of sealer. We diamond polish almost all the interior floors we make because we believe concrete floors ought to wear like a pair of blue jean, and one doesn't get the durability and graceful patina intuitively expected of a concrete floor without chemically hardening and diamond polishing it.
Most end up with stained concrete floors that are sealed, waxed and/or coated rather than chemically hardened and diamond polished for a lot of reasons. First off, it's much easier to do - so there are much more installers proposing to seal, wax or coat concrete instead of polishing. Secondly, it is faster/cheaper to apply sealer to concrete than polishing it. Also, most installers are nowhere near as concerned as we are about performance of the floor at year 5 or 10.