Keeping a Catalan vault when everything else goes

Almost every Eixample building put up between 1870 and 1930 has the same kind of ceiling: steel or timber beams with shallow arches of thin brick between them. In Catalan it is a volta catalana. In most renovations it is the first thing to disappear under plasterboard.

We think that is a mistake, and in most flats an avoidable one.

How a vault works

A Catalan vault is built from flat bricks laid in two or three layers with fast-setting plaster, without formwork. The arch carries the floor above by compression, so it needs little thickness to be strong. In the Eixample the vaults span between beams set 70 to 80 centimetres apart and rise only a few centimetres in the middle.

The technique is much older than the Eixample. Builders in Catalonia had used it for centuries in farmhouses and churches, and in the 1880s it became the standard way to floor a city block quickly and cheaply. The modernista architects later built stairs and whole roofs with it.

That shallow rise is what makes a room feel taller than its measurements. Light from the window runs along each curve and catches the edge of the next, so the ceiling has a rhythm even when the walls are plain. In the late afternoon, with the sun low, you can count the vaults from the door.

What can go wrong

The vaults themselves rarely fail. The beams are another matter. Steel rusts where a bathroom has leaked for decades, and timber rots where the roof has. Before we price a flat with vaults, we ask for a survey of the beams, and we tell the owner why. Vaults that have been covered for decades are often in better condition than exposed ones, because the plaster has protected them from damp.

Most problems show long before they become serious: a crack along a beam, a brown stain, a patch of plaster that sounds hollow when you knock on it. A structural engineer can check a whole flat in a morning. When a repair is needed, it is usually a steel plate bolted along the old beam, fitted from below without touching the floor above.

Keeping it

In the top floor at Consell de Cent the owners kept every vault in the flat. The plaster was taken back to the brick, the beams were cleaned, treated and painted, and the cracks were stitched with lime mortar. Insulation went on the roof above, so nothing covers the brick from below. New wiring runs in the floor rather than the ceiling, and the lights hang from the beams on short cables.

It cost more than plasterboard, but less than most owners expect, and it changed the price. Buyers notice a vaulted ceiling before they notice the kitchen. Over the last five years, Eixample flats we sold with exposed vaults found a buyer about two weeks sooner than comparable flats without them.

If you are about to renovate, ask your architect for one thing: open a small section of the ceiling in each room before you decide. What is under the plaster is often better than what you would put in its place.