Scan-to-BIM for a Heritage Seniors Home on Sherbourne Street, Toronto

Overview

237 Sherbourne Street sits in Toronto’s Garden District Heritage Conservation District. Built well over a century ago as a pair of brick-fronted, wood-framed semi-detached houses, it was converted to apartments in 1978 and is today a City-owned seniors residence, the William Dennison Apartments.

By the time iScano arrived, the building had been gutted to its structure. A Toronto architecture firm working with the City of Toronto had been engaged to retrofit it: preserve the heritage fabric of the house, and rebuild the interior as accessible senior living. The existing drawings could not be trusted for a structure this old and this altered, so every dimension the design depended on had to be measured, and measured to a standard that would also stand up as heritage documentation.

Why terrestrial, not mobile

Heritage work is one of the cases where the choice of scanner is not a matter of speed. A mobile (SLAM) scanner is the right tool for mapping large, regular spaces quickly; it is not the right tool for a building whose value lies in its arches, mouldings, irregular framing and a century of small deformations. Those need a stationary, high-precision terrestrial scanner: higher point density, lower noise, and geometry that holds to a few millimetres across the whole structure rather than drifting along a walked path.

This building was also going to be lived in. The architects needed millimetre-level geometry to design accessible units around the original walls and floors, and the City needed documentation of the heritage fabric that would remain valid long after construction. Terrestrial scanning gave both. For more on what that standard involves, see our guide to heritage-grade 3D laser scanning.

How it was done

1. Scope and control

We agreed the capture area with the architect, including the neighbouring buildings and site features the City would need for its review, and set out control so that every scan, interior, exterior and roof, would register into one coordinate system.

2. Interior and exterior capture

Every room, stair and opening was scanned from multiple stations, along with the full brick exterior, in about a day and a half on site. With the interior stripped to structure, the scanner recorded the framing, the openings that had been cut and re-cut over the decades, and the condition of what was left.

3. The roof junction

The most difficult part of the building was where the two original houses meet and the roof structure above the upper living quarters. From inside and from the street, those areas were partly hidden: the arched openings, the crevices where roof framing meets the party wall, and any deformation or damage in the roof structure could not be captured fully. Without them, the construction team would not have had the dimensional information needed to make changes there safely. So we scanned the roof itself. That closed the model from foundation to ridge and gave the architects the full envelope, including the sag, movement and past repairs that only show up when you can see the structure from above.

4. The basement, modelled as structure

The lower level was not modelled as surfaces but as structure: foundations, beams, posts and the timber joists carrying the floors above. Much of that timber had deteriorated over a century of use, and the retrofit loads would sit on it. The scan data, together with the site imagery captured alongside it, recorded the condition of the exposed timber, deflection, decay and past alterations, so the design team could assess how much of the central structure had been affected and what needed reinforcement or replacement.

5. Timber in the model

Framing members were modelled with their actual sizes and, where identifiable, the wood species, aligned directly to the point cloud rather than drawn from assumptions. The result is a drawing set that describes what is really in the walls and floors, which is what a heritage review and a structural engineer both need.

6. Drawings and clash checking

Plans, sections, internal elevations and reflected ceiling plans were produced from the model, along with a 2D CAD set. The same Revit model was set up for Navisworks so the design team could test the new mechanical, electrical and plumbing routes against the measured structure before anyone cut into it.

What the architects received, and what it did

The deliverable was an LOD 300–350 existing-conditions model in Revit, heritage-grade point cloud data, and a coordinated set of architectural and structural drawings. That one dataset did three jobs:

• Design. The architects laid out the new accessible units on measured geometry, not on assumptions, and cross-referenced the structural drawings with the construction team as work progressed.
• Construction. The crews on site worked from the same model and drawings, with the new services checked against the real structure in advance.
• Heritage review. The same documentation was reviewed and submitted to the City as formal heritage documentation of the building: a record of the house as it stood before the retrofit, usable long after the work is done.

That is the point of measuring a heritage house this carefully: the retrofit could preserve what makes it a heritage house, the brick façade, the arched openings, the original proportions, while the interior was rebuilt for the people who will live in it.

Project facts

Location	237 Sherbourne Street, Toronto: Garden District Heritage Conservation District
Building	Heritage semi-detached houses; 3 storeys + basement; converted to 11 apartments in 1978
Use	City-owned seniors residence
Client	Toronto architecture firm working with the City of Toronto
Method	High-precision terrestrial laser scanning; roof captured separately to close the envelope
Time	About a day and a half on site; model and drawing set delivered in roughly a week and a half
Model	Revit existing-conditions model, LOD 300–350, architectural and structural
Deliverables	Point cloud · Revit model · plans, sections, elevations, RCPs · 2D CAD · Navisworks model · heritage documentation

Planning a heritage retrofit? See our Scan-to-BIM services, 3D laser scanning in Toronto and our architecture and heritage work.