Museum Foundation RepairsPreserving our past for future generations
Cracks and holes in the rock retaining wall and adobe exterior wall on the west side of the building were discovered in 2020. Investigation by a team of structural and geotechnical engineers in 2021 determined the soil was settling beneath the southern portion of the building and the retaining wall below the adobe was sinking and moving outward towards Mission Blvd. This movement created exterior and interior cracks in the foundation, retaining wall, and adobe. It was also causing the exterior stucco and original mud plaster to spall off, exposing the underlying adobe to water damage. The engineering studies concluded the building was in danger of partial collapse in the event of a moderate earthquake on the nearby Hayward fault or a major earthquake on another Bay Area fault. Beginning in 2022 the parish has repaired the mission clay tile roof, replaced missing and leaking rain gutters, and replaced the failing sections of the foundation and retaining wall. Click here to see pictures of the foundation and retaining wall replacement, completed in February 2024. Help us preserve our 1809 Mission Museum for future generationsAs part of the Mission’s 225th anniversary we raised $100,000 towards the cost repairs. We also received $120,206 in grants from the Committee for the Restoration of Mission San Jose, a $25,000 grant from Alameda County, and $16,165 from the California Missions Foundation. The parish contributed $537,110 from parish savings for these repairs. More funding is needed to repair and restore the cracked and spalling stucco and mud plaster coating that covers and protects the building’s historic adobe brick walls, to repair and preserve the building’s wood windows and exterior doors, and improve restrooms. Click HERE to become part of our history with a donation to this project and to see a list of our donors. Foundation and Retaining Wall Repair Work ProgressJanuary 23, 2024 – The building foundation repair project is almost finished! Remaining work includes re-landscaping the construction area later this spring and applying a temporary waterproofing material over cracks in the exterior walls until additional funds are available to repair the mud plaster covering the original adobe brick walls using historically-appropriate methods.
January 9, 2024 – The completed retaining wall has been surfaced with stones salvaged from the original (now replaced) retaining wall. The next steps will be to uncover the windows and door and complete the replacement stair case. The original stairs had to be removed to provide construction access to the building foundation. The new staircase is an exact duplicate.
December 19, 2023 – Concrete for the new retaining wall being delivered.
December 15, 2023 – The concrete grade beam has been completed under the entire portion of the adobe wall that needed strengthening. The photo below shows workers adding steel reinforcement for the new concrete retaining wall in front of the grade beam.
December 2, 2023 – Grade beam construction is completed in sections before the remaining portions of the original retaining wall are removed. This provides continued support for museum’s adobe brick wall during the work. November 27, 2023 – Construction of the new concrete grade beam is underway. The poured-in place concrete will fill the remaining space between the underside of the adobe brick wall of the museum and the concrete columns injected into the soil. Notice the grade beam is being built in sections to ensure continued support for the adobe wall during construction of the grade beam. November 10, 2023 – All the injected cement columns have been completed. The next step is to remove the old rock retaining wall one section at a time and insert a steel and concrete grade beam between the bottom of the adobe wall and the top of the new concrete columns. October 9, 2023 – The drilling machine is injecting 4 to 5 soil cement columns daily. Note the grey tanks holding the cement that will be pumped to the drilling machine for injection into the soil beneath the museum to provide the missing foundation support under this part of the building.
September 29, 2023 –The soil cement injection drilling machine installed on its support structure. The machine will move horizontally along the front of the building on this temporary platform. September 22, 2023 – Plywood protection for the adobe walls and windows and noise insulation have been installed behind the green safety and security fence. Most of the major construction equipment has been delivered and staged. Scaffolding for the drilling rig has been built. This will be followed by testing to ensure everything is functioning properly. Foundation Problems DiscoveredThe building was constructed using typical mission-era practices. The walls are made of Adobe clay bricks and support roof trusses made of redwood. The building is the only surviving part of the original mission complex, most of which was destroyed in an 1868 earthquake. (The adjoining Mission church was completed in 1985 and is a replica of the 1809 church. Click here to read more about the history of Mission San Jose.) When cracks above the rock retaining wall on the Mission Blvd side of the museum began to appear the parish had a team of experts investigate in 2021. They discovered that, for reasons unknown, this part of the building was constructed on un-compacted native soil instead of a typical stone and compacted soil foundation. And the rock retaining wall in front of the building does not extend under the adobe wall and is starting to fall apart. Unless the missing foundation support for the adobe wall is created and the rock retaining wall replaced, this portion of the building could collapse in an earthquake.
Our engineering and geotechnical experts have created a plan to reinforce the foundation under this portion of the adobe wall. The existing rock retaining wall will be temporarily removed and the soil below the adobe brick wall will be injected with soil cement grout to fill existing voids and improve the strength of the subgrade soils. The subgrade soil will be jet-grouted to a depth of 8 feet below the base of the adobe brick wall and 2 feet laterally behind the face of the adobe brick wall. Temporary excavations are needed to provide access for the jet grouting drilling equipment. To prevent damage to the adobe wall, excavation will occur in six-foot sections, one section at a time. Following grouting of the subgrade, a new concrete retaining wall will be constructed in place of the existing rock retaining wall. The new retaining wall will be faced with some of the removed retaining wall rock to conceal the concrete structure. Repairs are on schedule for completion in January 2024.
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The Mission museum is the original 1809 adobe Convento, the former Padres’ living quarters. It is the oldest standing building in Alameda county. Its importance is recognized by the National Register of Historic Places and the California State Historic Landmarks Commission. 
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