Introduction
The Université de Sherbrooke needed an existing interior concrete slab demolished inside its Faculty of Science building so that foundations for a new addition could be prepared. What looked on paper like a routine demo became a complex problem: the existing slab proved to be far thicker and more heavily reinforced than the drawings indicated. Here’s how our crew adapted, kept the schedule, and delivered a clean foundation pad ready for the next contractor.
1. Site Assessment & Unexpected Conditions
Before breaking ground, our team reviewed the available structural drawings and coordinated access with the university’s facilities group. The first cuts told a different story: the slab carried several stacked layers of rebar that weren’t recorded on any plan. We paused, re-assessed loads, and adjusted our demolition approach so we could remove the slab safely without compromising the surrounding structure.
2. Heavy Demolition Evenings & Overnight
Because the building remained in active use during the day, the bulk of the breaking work was scheduled for evening and overnight shifts. The heavily reinforced slab demanded larger hydraulic breakers, controlled cutting sequences, and continuous debris removal so the work area stayed safe for the next shift. Working off-hours protected staff and students while keeping the project on schedule.
3. Excavation for the New Foundations
With the slab removed, the crew transitioned to excavation. Tight interior conditions meant working with compact equipment, careful spoil management, and constant elevation checks. Every cut was verified against the structural plans for the new addition so the next trade could pour footings with full confidence in the subgrade.
4. Pipework & Utility Installation
Underground services, drainage, sleeves and utility runs, were installed and tied into the existing systems before any backfill was placed. Sequencing the pipework correctly at this stage avoids opening the slab again later and keeps the building’s mechanical and electrical teams on track for tie-in.
5. Backfilling & Hand-Off
The final phase was structured backfilling in compacted lifts around the new foundation work. Each lift was tested before the next was placed, producing a stable, well-drained base for the addition. The site was then cleaned, secured, and handed back to the university ready for the structural contractor to take over.
Conclusion
Working inside a live academic building, on a slab that turned out to be twice as reinforced as planned, is exactly the kind of project that rewards experience. By rescheduling around campus activity, mobilising the right demolition tooling, and tightly sequencing excavation, utilities and backfill, A. Préfontaine & Associés delivered the Faculty of Science foundation pad on spec and on time, ready for the next phase of construction.
Are You a General Contractor?
We are the reliable subcontracting partner you’re looking for. Excavation, earthmoving, civil engineering let’s talk about your next project.