A lot of measurements taken from a stained-glass window of the eastern wall of the edifice, on the one hand inside the choir, on the other hand outside the church, makes possible to draw up the height of the base.

From the stained-glass window, measurements show us that the floor in the choir is 4m 50 highest than the lower part of the outside wall, unknown the thickness of that floor. It's allowed to imagine the inside of base arched hall-shaped, like a capitulary hall.