Press Releases


Replacement of the rib of one of the porch vaults

23/11/06 The damage was caused by water leaking from the roofs for many centuries.

While the strengthening works were being carried out on the portico vaults, a problem was detected in the diagonal joist of the vault belonging to the centre of the porch. This problem had been caused by uncontrolled water leakage from the roof over the centuries. This water contains soluble salts that are absorbed by the stone. When this water evaporates it increases in volume and breaks down the stone. This is a slow process but continues until the stone has literally disappeared.

The vaults of the Gothic fan-vaulting of the portico were erected with great structural stone arches that served as a frame for the stonework in the arches placed between them. The ogival joists form part of these main arches, which run diagonally across the covered space and fulfil a fundamental structural role.

To avoid the possible destruction of the vault that would have occurred in the mid-term, it was decided the complex job of substituting the joint would need to be undertaken.

The technical complexity of this operation consisted of preparing and installing a brace, or prosthesis, that would stimulate the structural role being carried out by the damaged joist and would act as a substitute.

This would then allow the portion of damaged joist to be removed so that prosthesis would hold up the vault, opening it up and leaving the arch stones uncovered.

Once the joist had been removed, the damaged arch stones were taken out and replaced with others made from natural stone similar to the originals.

The work was made even more complex due to the small amount of space available, and because in the central part of the damaged joint the vault has a carved keystone, which must be partly preserved (the carved part) and replaced at the end of the work.

Once the five arch stones have been substituted the joist must be replaced and the prosthesis must gradually be taken down.

Lastly, there is a check to make sure that the part of the joist that has been replaced is functioning correctly and the prosthesis is removed along with all the complex scaffolding necessary for carrying out the operation.