[ENG] Construction 96: Stone staircase (2) - the archway

10/11/17 | ۩ |

The construction of the stone staircase continues with the addition of new pieces, and is now ten steps high.
It lays over the vault of the service room hiding the woodshed, excepted for a thin split from which is still possible to peer inside.

At a lower level, the walls of the main entrance reached the base of the first stone rounded arch.

Here I have to spend some words to explain how I'm going to build the archway, getting inspired (for a change) by Viollet-le-Duc's illustrations.

Differently from the basement staircase, closed by a sole brick vault that follows the slope of the steps, this new structure will be entirely made of stone.
This responds not only to historical accuracy purposes on medieval genoese architecture, but it's also a visual choice. As the staircase represents the main access to the "noble" floor, it would look richer if built with solid stone instead of bricks.

The stairwell is placed inside the square perimeter of the tower, whose thick walls can easily bear the weight of the stone ceiling. Anyway, the cover of this room will not consist in a single sloping vault. It will be made with a sequence of round arches forming a sort of inverted staircase that will run parallel to the actual steps.

In the following pictures you can see the construction process of the first arch, using a coin as a temporary rib (I had to polish it on one side to adjust it to the arch diameter).

As I said, this is the very first of a long series of identical arches, so it's possible that some adjustment will be needed before the end of the work.
In fatct, every arch should correspond in height and width to a pair of steps, so to keep the same slope of the staircase. In this early test the height is clearly lower, resulting in a small nail shaped split that I'll need to fill with more stones.

As an alternative, I could build thicker arches (especially the middle ashlars) to avoid empty spaces when the full archway is assembled...

gray slate, vinyl glue
tweezers, pincers, files, sandstone, coin, cardboard, pencil
SIZES (in cm):
width: 1,2
ashlars height: 0,6
arch width 2,5
arch height 1,3

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