Presidio Chapel Historic Structure Report - Presidio Trust

HISTORIC STRUCTURE REPORTFINALConditionAs a utilitarian space, the boilerroom is in good condition,with only the window showingany signs of deterioration.Most of the boiler roomhallway features and finishesare also in good condition,but the extensive delaminationand efflorescence aroundthe ashpit door is illustrativeof a larger water infiltrationproblem originating at the topof the chimney and bell tower.Boiler room walls: board form concrete and clay tile.Efflorescence and staining from ashpit door.Issues & Recommendations• The roofing, flashing,and/or sealant at thechimney cap has failedImpact damage to interior corners of boiler room hall.and significant amountsof water is poolinginside the chimney aswell as along the chimney walls. Water infiltration, efflorescence, and plasterdelamination is concentrated at the bottom of the chimney surroundingthe ashpit door in the boiler room hall, but the source of the water clearlyoriginates at the top of the chimney. Efflorescence on the interior plastersurface suggests that water is being transported through the material, causingdelamination of the finish coat, and may be corroding the embedded steel.To alleviate delamination caused by efflorescence, the transportation ofwater through the concrete must be mitigated. A qualified structural engineershould assess the viability of the concrete. Once the chimney cap and flashingis repaired, then the plaster can be repaired using Big Wally’s Plaster Magicor similar product (see treatment of common materials below for repairs tointerior plaster).68MARCH 2012