Hi,
I am installing a new hardwood floor in a bar in Vienna Austria and need some advice please. The concrete floor is uneven and is heated by water coils. What is the correct procedure to lay a floor of 22 mm thickness. Will be appreciative of a reply. I want to be "educated" first prior to employing a local contractor

Just a observation probally from spending too many hours in establishments as yours, wood flors take a lot of abuse from spilled drinks, bar stools and neccesary routine maintence. I would go with something with a natural finish and nothing with a real smooth grain pattern like maple or beech. You will have to level the floor for a succesfull install and manufactures are picky about how and what floors can be put over this type floor system, you need to contact the manufacture of the flooring and get them to give you the specifics each method may be a little diffrent.

Thanks Kevin for that. I will probably use natural waxed Oak.

In a wet commercial setting, I would defiantly look for something that has been acrylic impregnated. I am assuming by you user name that it will be a real Pub. If you are looking for authentic flooring then you will have to look at European Oak, Birch, Beech or Scots Pine. Those are predominantly the woods found in Irish pubs.

Waxed is the worst choice possible for a bar floor. Every spill will stain the wax and it will require buffing. If the nightly routine will be to buff or re-wax the floor then this is not a problem but it will be a magnitude more labor. Creative use of Tung oil, stains, chemical processes and modern commercial finishes can give you the warm antique look of wax finishes without the problems.

is heated by water coils

Its basically radiant heating and it does cause some concerns when installing floors over. Some manufacturers will not warrantee their product over radiant heating. I don’t run into it a lot where I am at so someone else may be better suited to give you advice on this.

As Kevin said the floor needs to be even no high or low spots. It does not have to be level just even.

The wood floors in most Irish pubs are so battered up that you can just barely tell they're wood!. As a Dublin born Paddy I've picked up many a drunken friend from this type of floor.

Odds are good this floor won't be buffed or refinished very often (if ever) so something like tung oil will work good, it'll give it a slightly aged look.
Oak or Pine where used a lot

26 + 6 = 1. Erin go bragh!

Many thanks for that very helpful response. It gives me something to think about as I "impress" the contractor with my "knowledge".
Again thanks guys. Incidentally it will be the best Irish Bar in Austria.