What older built-up roofing assemblies can contain, why it has to be identified before disturbance, and what happens to a budget when it is not.
Tear-off on an older commercial building is not always just a matter of stripping membrane and hauling it to a landfill bin. Buildings constructed or last reroofed several decades ago can carry roofing materials that require special handling, and a contractor who treats every tear-off the same way, regardless of the building’s age, is setting a project up for a mid-job surprise.
This is not a niche concern in a city like Calgary, where a meaningful share of the commercial building stock dates back to the 1960s through the 1980s. Understanding what to look for before demolition starts, and what the process looks like when hazardous material is confirmed, is part of planning a tear-off responsibly rather than reactively.
Which Era of Assemblies Commonly Carried These Materials
Built-up roofing systems from roughly the mid-twentieth century through the 1980s frequently used asbestos as a reinforcing or stabilizing additive in several components: felt layers, mastics used at seams and penetrations, and flashing cements applied around parapets and curbs. This was standard industry practice at the time, not a defect specific to any one building or contractor.
A building’s age alone does not confirm what is present. Roofs get partially reroofed, patched, and layered over decades, which means a single low-slope roof assembly can contain a mix of older and newer materials stacked on top of each other. The only way to know what is actually in a given assembly is to test it, not to estimate based on the building’s construction date.
Why a Hazardous Materials Assessment Comes Before Disturbance
Alberta occupational health and safety requirements place a general obligation on employers and contractors to identify hazardous materials, including asbestos containing materials, before work that could disturb them begins. That obligation exists because disturbing these materials, through cutting, tearing, grinding, or heat application, is what releases fibers into the air where they become a health hazard for workers and anyone nearby.
In practical terms, this means a hazardous materials assessment, including sampling and lab testing of suspect components, needs to happen during the planning phase of a tear-off project, not once demolition is already underway. A contractor who skips this step is not just cutting a corner on paperwork. They are creating a genuine exposure risk for their own crew and taking on liability that a proper pre-assessment would have avoided entirely.
Advance Identification Versus a Mid-Tear-Off Discovery
There is a significant difference between finding out about hazardous material during pre-project planning and finding it after a crew has already opened up part of the roof. When material is identified in advance, it gets built into the project schedule and budget from the start: abatement is scoped, timelines account for it, and the client knows the number before work begins.
A mid-tear-off discovery is a different situation entirely. Work has to stop immediately in the affected area. The crew has to be pulled back, the site has to be secured, and an abatement contractor has to be brought in before demolition can resume in that section. That stoppage cascades into schedule delays on every other trade waiting on the roof to be ready, and it turns a budgeted line item into an unbudgeted change order negotiated under time pressure.
Coordinating With an Abatement Contractor
- Sampling results define exactly which components and locations require abatement before general tear-off can proceed
- A licensed abatement contractor handles removal of confirmed hazardous materials under controlled conditions
- The roofing contractor’s tear-off schedule is sequenced around abatement completion, not run concurrently with it
- Air clearance testing confirms the work area is safe before roofing crews resume normal tear-off activity
- Documentation from the abatement contractor becomes part of the project record for the building owner
This sequencing is not optional choreography. Running general demolition crews in an area before abatement is confirmed complete is exactly the scenario the advance assessment is meant to prevent, and it is where the real safety and liability exposure sits.
Disposal and Documentation
Materials confirmed as hazardous cannot go into a standard construction debris bin. They require handling, transport, and disposal through channels approved for that category of material, generally coordinated by the abatement contractor as part of their scope. A building owner should expect to receive documentation confirming proper disposal, not just a verbal assurance that it was handled.
That paperwork matters beyond the immediate project. A building’s hazardous materials history, including what was found, where, and how it was remediated, becomes useful information for the next renovation, sale, or reroof, saving the next contractor from starting the identification process from zero.
Owners who eventually sell or refinance the property benefit from having this documentation on file as well. A purchaser’s due diligence process on an older commercial building often asks directly about known hazardous materials history and how any confirmed material was handled, and a clean, organized record answers that question in minutes instead of triggering a fresh round of testing before the sale can close.
The Same Obligation Applies to Partial Work, Not Just Full Tear-Off
A full reroof is the obvious trigger for a hazardous materials assessment, but it is not the only one. Cutting a new curb for a rooftop unit, adding a penetration for new plumbing or electrical, or removing a section of old flashing during a partial repair on an older building can disturb the same category of materials as a complete tear-off. The disturbance is what matters, not the size of the project.
Building owners sometimes assume that a small scope, a single curb, a few feet of flashing, does not warrant the same pre-work assessment that a full reroof would trigger. That assumption is exactly where problems start. A five-minute cut into old flashing cement on a building from the wrong era carries the same exposure risk as a much larger project, and the obligation to identify what is being disturbed before work begins does not scale down with the size of the job.
This matters for facility managers scheduling routine rooftop equipment replacements or repairs on older buildings. A contractor doing that kind of smaller-scope work should be asking the same questions about the building’s age and material history that a full tear-off project would prompt, and should be prepared to pause and test before cutting into an unknown assembly rather than assuming a small job carries small risk.
Why the Reactive Approach Is the Expensive Path
Some contractors treat hazardous materials assessment as an optional step to skip on older buildings, on the assumption that they will simply deal with whatever turns up. That approach looks cheaper on the initial quote and almost always costs more in practice, once a mid-project stoppage, an unbudgeted abatement invoice negotiated with no leverage, and schedule delays on every downstream trade get added up.
The advance assessment is a small, known cost that buys certainty. A Calgary commercial roofing tear-off and replacement project on a building of unknown material history is exactly the kind of job where that certainty is worth paying for up front, rather than discovering the number under a work stoppage with the crew standing idle and the schedule already slipping.
What This Means for Budget Planning
For a building owner planning a reroof on an older commercial property, the practical takeaway is to build the hazardous materials assessment into the project timeline from the very first conversation with a contractor, not as an afterthought once a quote is already in hand. Ask directly what the assessment process looks like, how long lab results typically take, and how the contractor’s schedule accounts for the possibility of a positive result.
A contractor who cannot answer those questions clearly, or who suggests the assessment can be skipped to save time, is not doing a building owner a favor. They are shifting risk from the front of the project, where it is manageable and budgeted, to the middle of the project, where it is neither.
Plan for It, Do Not React to It
Older commercial roofs are not a liability to be avoided. They are simply a category of project that requires a different first step: identify what is actually in the assembly before anyone starts cutting into it. That step protects the crew doing the physical work, protects the building owner’s budget, and keeps a project on the schedule everyone agreed to at the outset.
A contractor who builds hazardous materials assessment into standard practice on older buildings, rather than treating it as a special case, is a contractor who has planned for the realities of Calgary’s building stock instead of hoping they will not come up.
About the author: this article was contributed by Superior Roofing Ltd., a Calgary commercial roofing contractor holding Euroshield certification alongside $10 million in liability coverage on every project. Red Seal journeymen lead tear-off and replacement work on older commercial buildings across Calgary, coordinating closely with specialty contractors whenever a project’s scope requires it.
