Long before most visitors to central Mexico know the name or the benefits of the area's familiar brick roof systems, they fall instantly, firmly in love with bóveda, the beautiful arched natural brick ceilings of the system. The first question from newcomers is always the same, "How do they do that?"
Bóveda is the Spanish word for an arch. It is also the word in Mexican and ancient Spanish architecture and construction, for a long, narrow section of arched brickwork. Sometimes the Spanish language seems amazingly limited in vocabulary. The dome of the heavens is called a bóveda—it's like the inside of a bowl. The arched ceiling cupped over the altar in old churches, the vault that is built to enclose a casket at the cemetery, and even the barrel-shaped ceiling over a hallway are also all called bóveda.
Bóveda is also the correct term for the 36" rows of brick arches that form the ceilings of many area homes. Each of these styles serves a unique purpose and is constructed a bit differently, but all are based on the ancient theory of the arch. The Romans proved the strength of arches to the rest of the world when they built the aqueducts. Once an arch is put under pressure or is bearing weight, it becomes even stronger. The success of bóveda depends on this same basic rule of physics.
Lakeside Bóveda History
Long before our Mexican neighbors began building Lakeside homes with low-arch bóveda ceilings, local masons were very familiar with the art. They used the technique for most burials at the local cemetery. Many families could only afford to buy a few lots in the cemetery. Knowing they would have many family members needing a final resting place, they had the plots dug extremely deep—deep enough to hold three or four or five bodies, stacked one on top of the other. Before the first family member died, the walls of the family plot were lined with brick. When it was time to bury the first body, the casket was lowered to the bottom of the hole and then the masons climbed down into the shaft and built a low-arch brick bóveda top over the casket, forming a crypt. When the casket was enclosed, the masons climbed out of the hole, and covered the hole with a removable slab of concrete.
Do you suppose this very real work is why we talk of seeking closure after the death of a loved one?
How do they do that? First, sufficient support
The starting point of every bóveda project is to ensure that the building's support structure is sturdy enough to bear the weight of all those extra bricks and the concrete layer that goes on top of the bricks to form a waterproof roof system. (See Brick: Lakeside’s Cornerstone, Part 7 The Roof )
Castillos are vertical open cages of reinforced steel that extend from deep in the footings up through the foundations and then to the intended roof line of the house. Interlocking the castillos at the top of the foundation is a dala (platform), which is a larger horizontal castillo. The dala is filled with concrete and gravel, and becomes a steel reinforced concrete platform on which to begin laying the brick walls.
As the workmen build the walls, they extend the bricks slightly into the vertical castillos at the corners of each room and about every four to six feet in between. This way the walls are locked into the castillos, which are then filled with concrete and rock to become vertical support pillars to support the roof.
At the top of the walls is another horizontal castillo, this one is a dala. It also is called the corona (crown). The building’s crown ties the entire structure firmly together when the steel-reinforced concrete vertical castillos are welded to the corona.
Bóveda—The ceiling of low arches
The ceiling-roof structure used almost exclusively in new Lakeside construction is the series of low-arch bóveda. Parallel brick arches form the ceilings of the rooms and are the base for a super strong roof that insulates the house from both the sun's heat and winter's chilly nights.
If the underground and wall support has been well planned, and if the castillos, dalas, and coronas are sufficiently large, this type of construction can easily support a second story.
On top of the corona 5" steel I-beams are welded into place and span the house at one-meter intervals. Then it is time for the abañiles, (brick masons) to start laying arches of bricks from one I-beam to the next.
Masons use a sercha as their guide (you can see the sercha in the photo above) when laying the bricks in each row of the bóvedas. The tool is less than the width of a single brick and fits into the ledges of the two I-beams. When the sercha is leveled and screwed tightly into place, the mason piles concrete onto the end and edge of each brick and places each on top of the curved guide until the new row of bricks reaches across the space from one I-bean to the other.
When the mason reaches the end of the row, he drives in a small rectangular piece of flint stone called a rajuela. This small spacer is the key to the success of this craft. Once the spacer is hammered into place between the last brick and the I-beam, it puts pressure on the arch and removes the danger of the arch falling. Once the arch is secure, the sercha can be moved forward along the I-beam to guide the next row into place.
After every three or four rows, the abañile and his helper smooth and shape the cement between the last few rows of bricks. The preferred tool for this job is a table knife. The men curl the tip, leaving a smooth surface the width of the cement grout.
The local masons prefer to lay no more than half meter to one meter (19-40") of bricks into arches, from I-beam to I-beam across the end of the building each day. Amazingly the newly laid rows of bricks are strong enough for the men to walk across in less than an hour, even when the rest of the ceiling has not been finished—and it's all due to the strength added by the pressure of that little rajuela.
Special thanks go to General Contractor Juan Gilberto Higuera and the maestros of The Little Company in Ajijic who explained procedures to me, answered questions and provided technical information for this article.