: you don't have to, but there are many ways to Rome and the same applies to house construction. : yes there are, the exterior wall is 17.5 cm, the base area has 14 cm thick insulation, then 16 cm on top.
17.5 only? Sand-lime brick? Do you know which one?
Yes, with the sand-lime brick the exterior walls are almost always 17.5 -er, inside there are also some 17.5 and 11.5 -er
They are sand-lime facing bricks