Techo vs. tejado
The words 'techo' and 'tejado' in Spanish both refer to the roof of a building, yet there exists a subtle distinction between their use and meaning based on regional contexts, architectural specifications and structural forms.
Techo
Techo generally refers to any kind of roof irrespective of the style or material used. Often, it can also indicate the ceiling inside a room.
El techo de mi casa es muy alto.
(The ceiling of my house is very high.)
Vivo bajo el mismo techo que mis padres.
(I live under the same roof as my parents.)
Estamos planeando instalar un techo verde.
(We are planning to install a green roof.)
Tejado
Tejado specifically refers to a sloping, tiled roof. It conveys a more visual and descriptive image of a typical, traditional styled roofing mostly found in Spain.
El tejado de la cabaña es rojo.
(The tiled roof of the cabin is red.)
El algodoncillo cubre el tejado como una manta blanca.
(The snow covers the tiled roof like a white blanket.)
La casa tiene un tejado de tejas viejas y rotas.
(The house has a tile roof made of old broken tiles.)
Summary
'Techo' and 'tejado' both mean roof in Spanish, but they are used slightly differently based on context. While 'techo' could be used to describe any type of roof or even ceilings within a building, 'tejado' specifically refers to traditional sloping, tiled roofs.