Yup, but "to be stupid like a brick" does exist and it is used around... or if not around, at least, parallelepiped-ly,
In Spain there is also the usage of "tocho", particularly for books,
DRAE,
tocho
3. m. coloq. Número considerable de papeles escritos.
Un tocho de apuntes de clase.4. m. Libro de muchas páginas.
Ha publicado un tocho de mil páginas.
Tocho is actually a 'brick' or an 'iron ingot'... (the sense of "tocho = brick" it is probably a Catalonia usage, as it is not in DRAE nor Moliner.)
La novela es un tocho, o más pesada que un ladrillo... un plomazo que no veas... (These are common expressions in Spanish.)