That is the case where i am learning Spanish, techo, roof, cielo, cieling. I think the reason they call it cielo is because when you look up at the cieling , you are looking in the direction of the heavens, and cielo means heaven, so thats where the word got its meaning most likely.
I'm sorry, are what the ones used in Spain? If you mean which words do they prefer, I've heard that they prefer 'tejado' for all roofs and 'techo' for 'ceiling' in Spain. I'm used to only using 'tejado' for tiled ceilings, but apparently this is different in Spain. I don't think they ever use the word 'cielo' for describing a part of a house. This may vary by region in Spain as a few other things do. You'd have to ask people from all over Spain. In Latin America, usage varies, sometimes even within one country. You'd have to find out from the locals which words are preferred. Maybe Babella will come back to Duolandia sometime soon and give us a perspective from Spain.
techo. (Del lat. tectum). 1. m. Parte superior de un edificio, que lo cubre y cierra, o de cualquiera de las estancias que lo componen. 2. m. Cara inferior del techo, superficie que cierra en lo alto una habitación o espacio cubierto.
tejado. 1. m. Parte superior del edificio, cubierta comúnmente por tejas.
Techo 1. male. Top part of a building, which covers and closes it, or of any of the rooms that compose it. 2.male. Low face of the ceiling, surface that closes in high a room or covered space.
Tejado. 1.male.Top part of the building, covered commonly for tiles.
These are the official definitions.
I am spanish, I use techo for ceiling and Tejado for roof.