Historic Versailles Hotel: board approves detailed plan for three‑level basement and strict monitoring conditions

The Historic Preservation Board on May approved a certificate of appropriateness allowing the excavation and construction of a three‑level basement beneath portions of the contributing Versailles Hotel at 3425 Collins Avenue, contingent on new monitoring and reporting requirements meant to reduce risk to the historic fabric.

Board members approved the plan after a detailed presentation from the applicant’s engineering team showing sequencing, soil‑improvement and shoring measures designed to preserve the existing structure while construction proceeds beneath it.

The board’s vote came after the applicant’s engineers described a staged approach in which temporary shoring towers and steel platforms would support the building while auger‑cast and jet‑grouted piles and pile caps are installed, columns are jacketed and new internal slabs are built. “We are going to improve the soils around the building,” said shoring engineer Youssef Hashim, describing a mix of deep‑soil mixing and jet grouting to create hard, load‑bearing soil blocks around and beneath the structure. “We are not pounding or vibrating anything. It’s going to be augering — very low impact construction.”

Staff said the additional technical submissions received since the board’s earlier review — including letters from Keller (foundation contractor), Desimone (structural), and NV5 (geotechnical) — supported the proposal but recommended conditions to lower implementation risk. Those conditions adopted by the board require, among other things, a pre‑issuance letter from the project structural engineer that identifies “critical events” that would render the building most vulnerable, on‑site supervision by the structural/shoring engineer of record during those critical events, continuous vibration monitoring with alert thresholds, and a requirement that the applicant notify the planning department no later than the next business day if any indication of structural compromise appears during work.

The applicant’s team, which included Keller North America, Desimone Consulting Engineering and NV5, walked the board through the staged plan — installing perimeter soil‑mixing, driving auger‑cast piles for temporary towers, constructing pile caps and steel platforms under the existing floors, removing interior slabs to get headroom, improving soils inside the footprint and then installing interior piles and new columns and slabs in a progressive sequence up to the roof. Desimone’s structural engineer said the approach creates a new internal structure that will be connected to the existing exterior via drilled and epoxied anchors and concrete jackets around existing columns.

Public commenters included preservation advocates who called the project “fascinating” and urged strong oversight; several engineers present described similar projects in South Florida completed with success. The board discussed worst‑case scenarios and legal remedies. City staff explained that if construction were to exceed the scope of work approved by the board (for example, collapse requiring demolition), the historic preservation ordinance allows the board to require reconstruction; after‑the‑fact demolition would be subject to an after‑the‑fact certificate of appropriateness and code enforcement.

The board approved the certificate of appropriateness by roll call (Weinstein Berman, Paschal, Lopez, Litt, Liebman, Klein, Finglas — yes) with the additional conditions described above. The applicant agreed to the monitoring and reporting language and to provide a more detailed construction schedule and the on‑site supervision plan before building‑permit issuance.

The approval authorizes the structural approach as presented and requires the applicant to return to staff (and the board if required) with any significant deviations or if the monitoring data indicate compromise.

For residents and neighbors, the work is likely to be noisy and staged over months; the applicant estimated the sequence of structural restoration would take on the order of 18 months from the start of this portion of work. The board’s adopted conditions are intended to ensure early detection of structural problems and rapid notification to city staff so the board can exercise its authority if an emergency or demolition‑level event occurs.