The original nucleus of the Holy House consists of only three walls, because at Nazareth, in the wing where the altar now stands there had been no wall as that side opened onto the entrance of the grotto.

The lower sections, to a height of almost three metres, of the three original walls consist mainly of rows of gravel stones, that could be found in Nazareth, while the upper section, wich are later, spurious additions, are made of local brick, the only building material used in the Marche.