I worked for a commercial greenhouse that had rough finished concrete walkways in some of their greenhouses. Even with the rough finish the walks would over time become slick with a green slippery moss that grew under the benches, and would eventually work its way into the walks. Periodic washings with a pretty strong Clorox solution would fix it for a while, but......

We were growing orchids/indoor foliage, so were throwing a good deal of water at a lot of plants.

Bill

I have concrete that is sloped towards a trench drain the runs across the structure. I do have to spray a bleach solution on it to keep algae in check. This only takes a few minutes. I have radiant heat in my floor and am happy with it.

My greenhouse floor is about 8 inches of gravel. It's easier on my feet, very stable to walk on, and I enjoy finding self sown seedlings from cyclamen and the like. If we ever get any low humidity days (which are few in my climate), I water the gravel, and on summer days when the residual water in my long hose is too hot for watering plants I just spray it into the floor until the cooler water from the pipes gets to the nozzle.

My GH floor is pavers on a sand bed, with sand in the joints. When I have spills, the water goes through the sand joints and I never have a slipperiness problem or algae growth.

The floor in my small greenhouse: