Presidio Chapel Historic Structure Report - Presidio Trust

PRESIDIO CHAPEL (BUILDING 130)SAN FRANCISCO, CALIFORNIAcases, corrosion. There is also some staining and plastercracks in the bell tower stairwell, bride’s room, and bride’sroom hall.Efflorescence is concentrated in areas of visible waterintrusion. Efflorescence, the expansion of salts below thepaint surface, may cause delamination of the finish coat.Although generally uncommon in the Presidio Chapel,efflorescence is visible adjacent to the Hope window inthe chancel, along the concrete apron of the basement, atthe union of the bell tower and sanctuary, within the belltower, and in the organ pipe chambers above the vestryand the bride’s room. To alleviate delamination causedby efflorescence, the transportation of water through theconcrete must be mitigated.Example of corrosion and spalling in organ pipe chamber.Efflorescence and staining at ashpit door.In the case of the bell tower, the path of water can be tracedfrom the chimney where flashing has presumably failed, allthe way down to the lower level. Staining is evident at alllevels of the tower, ultimately manifest at the ashpit door inthe boiler room hallway. Water collecting at this lowest pointhas caused efflorescence and delamination. Repairs and/orreplacement of the chimney flashing or chimney cap shouldalleviate the problem.PART III: TREATMENTRECOMMENDATIONSCONCRETEReinforced concrete masonry is the primary structuralmaterial at the Presidio Chapel. As such, steel reinforcingbars known as “rebar” are imbedded into the concrete toincrease the tensile strength of the material. Lateral (windor seismic) loads are resisted by the existing concrete wallsacting as shear walls in combination with the wood roofsheathing and the concrete ground floor slabs acting asWater staining along chimney mass in bell tower.Efflorescence and spalling in bell tower.Page & Turnbull49