I think you are right. Today the cement is starting to cure and getting harder so it think it will be ok.
I did go out buy the primer for the rest of the job and its dead simple to use and my guess is that it is just acrylic, same as what gets added to mortar to make it stronger so it increases adhesion right at the surface.
> I am not from cold country (san diego ) I was wondering how the wood would hold up to the heat
A few years ago most radiant heating suppliers were saying "tile only" but recently both the heating and flooring suppliers say engineered wood floors are okay over radiant flooring. Floor warming system are pretty low power, for example, 15 watts per square foot so you can imagine that the 15 watt light bulb wouldn't be a lot of heat to put to a piece of wood, especially multiply wood flooring.
Also, I'm not *heating* the room with the floor system, it also has forced air. The radiant floor system is just to keep the draft off of the floor: one whole wall is a glass solarium so while its very well insulated glass its cools the surface of floor on wicked cold days. The solarium company recommended radiant floor warming as being a very nice to have with this arrangement.
thanks for the advice.