OK again a show of hands (or a definitive answer if there is one!!) please.

Do people apply an elevation figure to the Survey Point or Project Base Point? Or does it depend on whether you have received elevation information from an OS / survey file or whether it's simply related to an arbitrary level such as a floor?

I've looked at loads of guides all of which seem to discuss the differences between the 2 points based on the Northings, Eastings part but neglect to mention the elevation part.