Overview
Two buildings were going up in Rosedale, boutique residential. The glass installation contractor came to us with a problem we hear a lot: the architectural drawings show the openings one way, the building gets built another way, and the glass has to fit the building, not the drawing. They wanted to skip the tape measure. Give us CAD outlines of every opening, and show us how the glass sits against the structure.
So the ask was as-builts of the whole site. Both buildings, the lot around them, and the garage, because they wanted to see the structure in context and not just one opening at a time. Mostly 2D CAD, with a 3D model behind it.
The scan itself is only half of this story. The other half is the gap between what a client thinks they are getting when they hear “laser scanning” and what a survey-grade dataset actually is, and what it took to close that gap. That is the part worth reading if you are a glazier.
What we were given
- Two buildings under construction, a full lot and a garage, on a dense residential street with real site-safety constraints
- Architectural elevations with every glass opening numbered
- A contractor who worked in 2D CAD and wanted to bring 3D and Revit into their workflow for the first time
- A glass fabricator downstream who cut from 2D CAD in their own template
What we delivered
- Registered, high-density terrestrial point cloud of both buildings, the lot and the garage
- A decimated working copy of the cloud and a free online viewer for quick measurements
- Point cloud tied into the project surveyor’s control coordinate system
- 2D AutoCAD opening drawings and elevations, with clearances, re-issued in the fabricator’s own CAD template
- Revit as-built model of both buildings, with IFC export
How it was done
1. Capture
About three and a half days on site. It was an active construction site, tight access, and there were real limits on where we could safely stand, so almost everything was done with a terrestrial scanner on a tripod rather than a mobile unit. Slower, but it was the only safe way to get the density the openings needed. Both buildings, the lot and the garage, all scanned at high density and registered into one point cloud.
2. The dataset was the first problem
High density across a whole site means a big file. The registered cloud came in around 50 to 60 GB. The client was expecting something closer to Matterport, a walkthrough you open in a browser and click around. A survey-grade point cloud is not that. It needs a proper workstation and point-cloud software, and the first time you open one it is a lot. The first reaction was hesitation, which to be honest is the normal reaction.
3. Making the data usable
Two things fixed it. We decimated the cloud by a few millimetres into a working copy that moves comfortably on a normal machine, and we set up a free online viewer so their team could walk through both buildings on screen and pull quick measurements without buying or learning anything. The full-resolution data was still there for anything that needed it.
4. Tying it to survey control
The project already had surveyors. We got in touch with them, got their control network, and merged our point cloud into the same coordinate system. Now every opening and every slab edge was sitting on the same grid the rest of the project was using. That tightened the data up and, just as important, gave everyone one reference to work from instead of arguing about whose numbers were right.
5. Clearances
This was the turning point. A scan tells you the size of the opening as it is. It does not tell you the size of glass to order. The contractor was reading the drawings as one to one, opening equals glass, and there is no such thing. Every installation needs clearance for the frame, the gaskets, the tolerance of the opening itself and the movement of the building. The moment we put clearances on the drawings as their own variable, the numbers made sense, the calculations worked, and the whole tone of the project changed. Nothing about the data changed. What changed was how it was being read.
6. Drawings the fabricator could cut from
The people cutting the glass worked from 2D CAD in their own template, and our first CAD set, correct as it was, was not in that format. So the contractor sat down with the fabricator, the fabricator sent over their template, and our design team re-issued the opening drawings in it. After that it ran the way it should: scan, CAD in the fabricator’s template with clearances, cut, install.
The outcome
Once those four things were in place, a viewer the team could actually open, the cloud on the surveyor’s grid, clearances on the drawings, and CAD in the fabricator’s template, the contractor had a workflow they could fabricate from, based on what was built and not on what the architect drew. The glass and frames were made and installed to the as-built openings, the fabricator cut from drawings in their own format, and the extra time on this job went into getting everyone on the same page, not into going back to re-measure the building. At the end of it, everyone was happy. It just took a few more pieces of information than anyone expected at the start.
What we learned, and what a glazing contractor should know before ordering a scan
- Don’t assume 1 mm just because it’s a laser scanner. Installers ask for millimetre-perfect openings all the time. A 1 mm tolerance across a whole project is a real specification, with its own equipment, setup and method, and it is not what a scan gives you by default. On this job the registered scan gave us the few millimetres the openings needed, and the clearances were handled as a separate variable on top of that. Agree on the accuracy, the registration, the survey control and the clearances before the scanner comes out of the case.
- A point cloud is not a 3D tour. Decide up front how your team is going to look at the data: a viewer, a lighter working copy, or the full dataset on a workstation. If in doubt, ask for the viewer.
- Find out who cuts the glass and what they cut from. If the fabricator works in 2D CAD in their own template, that is the format the drawings need to go out in, whatever 3D model is sitting behind them. Ask before the first drawing gets made, not after.
- If there is a surveyor on the project, tie the scan to their control. It costs very little and it takes a whole category of arguments off the table.
- Be clear about what you are buying, and be clear about what you are selling. The scan went fine. The delays came from expectations on both sides, and fixing that took conversations, not another scan. Small misunderstandings about deliverables turn into big delays on site, and this one taught us to have those conversations first.
What we deliver for glazing work now
Since this project, every glazing or curtain-wall job we quote starts with three questions. What are you going to open the data in? Who cuts the glass, and what format do they cut from? And what clearance rule do you want on the drawings? Then we deliver a viewer, a point cloud tied to survey control, and 2D CAD in the fabricator’s template. The 3D model is there to support it, not the other way around.
Fitting glass to a building that is still going up? Have a look at 3D laser scanning in Toronto, our as-built documentation service and Scan-to-BIM services, or read about the difference between static and mobile LiDAR.
