recessions especially whenever this is more easily done when building the forms in which the corresponding base plates are foam molded than it would be to shape the angular pieces illustrated in the drawing nor was consideration given in the illustration to the formation of curvature radii etc the person skilled in the field of tile laying does not require further explanation to know that provisions for this need to be made it is possible especially when integral foam molded positioning devices are used to use these for positioning at a right angle to the level of the tiles as well for this purpose the height of the positioning elements must match and be limited in order to prevent a vertical displacement of the tiles to one another fig1 and 13 do not show a heating system this can be easily provided however just as with the other illustrated variants fig1 and 15 show especially preferred variants of the invention with which a very simple and yet especially precise installation of the tiles can be accomplished for this purpose in the illustrated embodiment an installation strip 40 49 is attached to the floor or substrate or subfloor 30 for example by means of the depicted screws 41 the installation strip 40 49 bears projections 42 43 and can if necessary also have recesses not shown the installation strip 40 49 makes contact with the floor 30 by means of an equalizing layer 50 with the help of this equalizing layer contact over the.