Texas Heritage, Fall 1983

been removed from parapets and soft plaster installed. Leaking windows
have been repaired and screens installed so that natural ventilation can be
utilized.
Overlays of hard cement mortar pointing, often smeared over the
surface of the stones were systematically removed where possible without
damaging the stones. Repointing is then done with proper joints and
compatible mortar.
In the natural weathering process of the stone, as rain enters in and
evaporates from its exterior, dissolved minerals are deposited on the
surface forming a hard crust. Care is taken to avoid disturbing this crust
because once it is dislodged, the leached area behind is quite soft to a
depth of about one inch before an unaffected limestone surface is
encountered.
Occasionally, where the methods used in the original construction
hasten the destruction of building elements, little can be done. The lower
portion of the facade of Mission Concepci6n contains carved stone
pilasters that were installed with the sedimentary grain of the limestone
perpendicular to the ground. Moisture entering these stones is drawn in
farther than normal and instead of migrating to the exposed face of the
stone, must evaporate at the mortar joint. Over the years, entrapped
moisture has frozen, expanded and caused the surface layers to fall away,
much like slices from a loaf of bread. No structural undermining has
resulted so far and at present, observation is the only action being taken.
We are fortunate to have relatively clean air in San Antonio, and
barring heavy industrial development to the South, anticipate a minimum
amount of acid rain in the near future. The locations of the Missions to the
Southeast of the city - upwind in the prevailing breeze, augurs well for
freedom from future pollutants generated in the city proper.
Moisture entering the walls from the ground exists at all of the
Missions. Called "rising-damp," this absorption through capillary action
and subsequent migration of moisture up the walls grows because of the
increase in the capacity of the limestone to hold water due to the salts
brought into the stone with the ground water.
This condition is manifested most severely at Mission Concepcion
where moisture rising from the ground has intensified the deterioration of
the lower pilasters in the carved facade as well as some of the carved
stone above that level and the facings of stones on the lower exterior
walls. Salts crystalize on the interior walls to a height of six feet above the
floor.
At Mission San Jos6, over one third of the Mission grounds drain
toward the Church and Sacristy building, causing the outside ground to
build up over the years to a level two feet above the floor level on the
interior. This compounds the problem by adding more soil surface of the
stone through which moisture can migrate.
The remedy for rising damp is to insert a barrier at grade level
stopping the upward migration of the moisture, however the cost of
performing this procedure on the two-to-four-foot thick rubble limestone
walls is prohibitive. With the separation of responsibility between the
Catholic Church and the National Park Service for the secular and nonsecular
structures, the burden of financing the repairs for the portions of
the Missions used for religious purposes falls on the Archdiocese. Moneys
are sought for ongoing stabilization from private sources, limiting the
amount of work possible.
The buildings though basically stable have manifested structural
problems throughout their existence. Over the past three years structural
cracks have been monitored with dial and electronic gauges through a
cooperative program between the Archdiocese of San Antonio and The
National Park Service. One crack under scrutiny appears in an 1890
photograph of the Sacristy at San Jose. Of particular concern is the now
documented outward movement to the north of the Convento wall at San
Jose. The National Park Service recently stabilized a 1930's reconstructed
archway at San Jose by shoring its foundation.

The famous "Rose Window" presently with temporary shoring has
suffered settling movement caused by the failure of mortar in the
keystones of its arch due to water in the wall. This will be corrected in the
current phase of work by regrouting the keystones in alternate layers.
Much concern has been focused on recent movement at Missions San
Juan Capistrano and Espada. Emergency shoring for portions of the
compound walls has been erected. Interestingly, the analysis of test holes
drilled at both Missions indicated that expansive soils are not the cause of
the movement.
The most recent cracks in San Juan Capistrano were caused by
drilling for utility installations near the foundations, causing the gravel
substrate to settle. This movement has stabilized.
The problems at Mission Espada are more complex. In 1870 before
Father Bouchu reconstructed the church, all that was standing was the bell
tower facade with its moorish doorway. Now this wall is moving away
from the nave and transepts erected by Bouchu. In addition, arches in the
1930's collonade abuting the south wall of the nave are thrusting against
the walls causing visible movement. Inside the Friary, the east-west cross
walls are thrusting the west wall outward (the east wall is stabilized by
buttresses), and on the roof of the Church, improperly installed air
conditioners are causing the interior plaster to vibrate from the walls.
Projected work here includes tie rods to anchor the bell tower to the
body of the church, buttresses to counterbalance the forces thrusting on
the west wall and isolation of the vibration sources.
The years have taught that these Mission structures remain dynamic.
Their stabilization and preservation is an on-going effort, both to
understand the causes of the problems and to effect a solution that keeps
balance.
Carolyn Peterson, A.I.A.
Principal, Ford, Powell & Carson

Pedro Huizar is credited as sculptor of the "Rose Window" and the facade
of San Josd, the "Queen of the Missions." 1920's photograph courtesy San
Antonio Conservation Society.

Insert to Texas Heritage

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Texas Historical Foundation. Texas Heritage, Fall 1983. The Portal to Texas History. http://texashistory.unt.edu/ark:/67531/metapth45449/. Accessed January 24, 2015.