The height

For additional saving funds, you can not extradite the sockets on the balcony and by the external installation — see. photo.

In order to choose the optimal heating cable, you can contact specialists or make a warm flooring calculation online by setting the required area and focusing on a fairly high power of about 200 watts per square meter (depending on the quality of the balcony insulation, but the general rule is better than more than than less). The cable in the screed will be cheaper and warm better than the mat, even with increased power, but designed for installation in tile glue. The latter option can only be recommended if the loggia is well insulated, and the option with the screed for some reason is unrealistic, for example, there is no way to raise the height of the floor.