Commercial mould remediation in Toronto and the GTA is specialist work, and Zusashi does not do it. This page exists because building owners, property managers and facility managers ask us about mould all the time — usually because we are already in the building doing something else — and sending them away with nothing has never felt like an answer.
How this works
Zusashi has been cleaning commercial buildings across the Greater Toronto Area since 2007. Spend that long in one trade in one region and you come to know the businesses around you — who has been doing remediation properly for years, whose name keeps coming up for the right reasons, and who you would steer a client away from. Reputation travels in this business. We have been here long enough to hear it.
So when you have mould in your building, we can point you toward an established contractor instead of leaving you to pick a name out of a search result. Here is exactly what that is:
- We don’t remediate mould. It is a specialist trade with its own containment, equipment and training — not what our crews do. We would rather say so in the first line than work it out with you halfway through the job.
- We’ll give you a name worth calling. A firm that has been doing this work for years and has the reputation to show for it, rather than a name pulled off a directory.
- You deal with them directly. The site visit, the quote, the contract and the work are between you and them.
- We can shorten your list. The last check is yours — and it is a short one. We have written down exactly what to ask them, so it takes about five minutes.
No cost to you, no obligation. And if it turns out to be a cleaning job rather than a remediation job, we’ll tell you that too.
Is it a cleaning job or a remediation job?
This is the question almost everyone is really asking, and it has a reasonably clear answer. The Canadian Centre for Occupational Health and Safety publishes size thresholds that the trade works to:
| How much you can see | What that usually means |
|---|
| Small — one to three patches, each under 1 m² (about 10 sq ft) |
Surface cleaning with proper precautions. CCOHS puts the minimum at an N-95 respirator plus gloves and eye protection. |
| Medium — more than three patches, or patches of 1–3 m² (10–32 sq ft) |
The same work with stepped-up controls, and a point at which most operators want somebody who does this for a living. |
| Large — over 3 m² (32 sq ft), or heavy contamination |
CCOHS is explicit that large remediation projects should be done by trained professionals. This is the referral. |
Size is not the only test. Mould inside a wall cavity, above a ceiling, in insulation, or anywhere in the HVAC system is a remediation job whatever area it appears to cover, because the visible patch tells you nothing about the extent behind it. The same goes for anything that has been wet for more than a couple of days, and anything in a building where people have started reporting symptoms.
One practical note from the same source that gets missed constantly: the HVAC system should be off during cleaning. Running it turns a contained problem into a distributed one.
What mould actually looks like in a commercial building
Very little of what is written about mould is written for someone running a building. It is nearly all homeowner advice about bathroom grout. The commercial version tends to show up in a handful of predictable places:
- Ceiling tiles with a brown halo, usually under a roof penetration, a rooftop unit or a floor with plumbing above it. The stain is older than the day you noticed it.
- Perimeter walls and window returns in an office where warm inside air meets a cold surface all winter. No leak, just condensation doing the same job more slowly.
- Warehouse and cold storage envelopes, where a temperature difference across a wall or a dock door produces condensation on a schedule.
- Behind millwork, under sinks and inside service risers — the slow weep nobody sees for a year.
- Condo and multi-unit common elements, where the corporation carries the repair duty for the common element and a unit owner is reporting a smell.
- After a leak or a flood, when a space was dried out quickly but not thoroughly, or was closed up while still damp.
In almost every one of those, the mould is the symptom and water is the problem. A contractor who quotes to remove it without asking where the moisture comes from is quoting you for a repeat visit.
What to ask them before you sign
This is the five-minute check, and it is the same one we would run ourselves. Worth having in front of you on the call — whether the name came from us or from anywhere else.
- Ask what certification they hold, and ask for the certificate. There is no mould remediation licence in Ontario — anyone claiming one is describing something the province does not issue — so certification and insurance are what you are actually verifying.
- Ask for a current liability certificate and WSIB clearance. Same two documents you should be asking any contractor for, us included.
- Ask how they will find and fix the water source, not just the growth. If that is not in the scope, the job is not finished when they leave.
- Ask about asbestos if the building has any age to it. Opening up walls, ceilings, insulation or flooring is where that risk lives, and unlike mould it is regulated.
- Ask how the area will be contained and how the rest of the building keeps operating while the work runs.
- Ask what proof you get at the end — what was removed, what was treated, and whether any post-remediation verification is included.
- Get it in writing before anyone starts. A verbal scope on a mould job is how disputes begin.
What Zusashi does handle
So the boundary is clear in both directions, here is the work on this subject that is genuinely ours:
- The clean after remediation. Once the contractor has finished and released the space, the building has to go back into service — settled dust on every surface and ledge, floors, carpets, washrooms, corridors, common areas. That is ordinary commercial cleaning and we do it. It is the same arrangement we already have on water damage: a restoration contractor dries and clears the space, we handle the clean that follows.
- The cleaning that stops it starting. Washroom and kitchen extract grilles, drains, condensate trays, hard floors dried rather than left wet, carpets extracted and properly dried rather than over-wetted. None of this is glamorous and all of it is cheaper than remediation.
- Telling you which one you have. Describe what you are looking at and we will give you a straight answer about whether it needs a specialist, including when it doesn’t.
Tell us what you’re dealing with
Where the building is, what you can see, roughly how big an area, and whether you know where the water is coming from. A photograph helps more than anything else. We will pass it to a remediation contractor so they can contact you, and that is the extent of it — you deal with them directly, and checking their certification, insurance and references is yours to do.
Send us the details
By getting in touch you agree we may pass your details to a mould remediation contractor so they can contact you about this enquiry. We do not remediate mould ourselves and we are not a party to any work you agree with them. See how referrals work.
Commercial mould remediation — frequently asked questions
Do you do mould remediation?
No. Mould remediation is a specialist trade — containment, negative air, removal of contaminated building materials, and clearance before the space goes back into use. It needs its own equipment and its own training, and it is not what our crews do. We would rather tell you that in the first line than take the call and work it out later. What we can do is put you in front of a remediation contractor with an established reputation, at no cost to you.
How do you know who to refer me to, if you do not do the work yourselves?
We have been cleaning commercial buildings across the GTA since 2007. Spend that long in one trade in one region and you come to know the businesses around you — who has been doing remediation properly for years, whose name keeps coming up for the right reasons, and who you would steer a client away from. Reputation travels in this business. To be straight with you about what that is and is not: we are going on reputation and time in the industry, not on having supervised their jobs. We can shorten your list. We cannot do your due diligence for you.
Is a mould remediation contractor licensed in Ontario?
Not in the way people assume, and this is worth knowing before you hire anyone. Ontario regulates asbestos work in detail — work is classified Type 1, 2 or 3, training is mandatory, and the Ministry has to be notified before certain projects start. There is no equivalent licensing regime for mould. The Canadian Centre for Occupational Health and Safety talks about “trained professionals”, not licensed ones. So what you are actually checking for is certification and insurance: relevant remediation certification, a current liability policy, WSIB clearance, and references from jobs like yours. Anyone advertising a mould licence is describing something Ontario does not issue.
Is this a cleaning job or a remediation job?
Size is the usual dividing line, and CCOHS publishes the thresholds. Up to three patches each under one square metre (about 10 sq ft) is a small isolated area. More than three patches, or patches between one and three square metres (10–32 sq ft), is a medium job with stepped-up controls. Anything over three square metres (32 sq ft), or heavily contaminated, should be done by trained professionals. But size is not the only test: mould inside a wall cavity, above a ceiling, in insulation or in the HVAC system is a remediation job whatever its area, because you cannot judge the extent of what you cannot see. If you are unsure, tell us what you are looking at and we will tell you honestly which it is.
What happens after I send the form?
We read it, and we pass your name, your contact details and what you have described to a remediation contractor so they can get in touch. That is the whole mechanism. From that point you deal with them directly — the site visit, the quote, the contract and the work are between you and them, and we are not a party to any of it. There is no cost to you and no obligation to go ahead with anyone.
Why does mould keep coming back after it has been cleaned?
Because mould is a symptom, and wiping it off treats the symptom. It needs moisture to grow, so unless the water source is found and fixed — a roof leak, a failed seal, condensation on a cold surface, a slow plumbing weep, poor drainage against a wall, humidity with nowhere to go — it returns to the same spot. This is the single most common reason a building has a “mould problem” year after year: somebody has been cleaning it repeatedly and nobody has fixed the water. Any contractor who quotes you for removal without asking where the moisture is coming from is quoting you for a repeat visit.
Could there be asbestos as well?
In an older building, yes, and it matters a great deal. Mould remediation means opening things up — drywall, ceiling tiles, insulation, flooring — and in a building of a certain age those materials can contain asbestos. Unlike mould, asbestos is regulated in Ontario: work is classified Type 1, 2 or 3 by the hazard, training is mandatory, and there are notification and procedural requirements before a project starts. A competent remediation contractor will raise this before demolition begins. If they do not, ask.
Do you clean up after the remediation contractor has finished?
Yes, and this is the part that is genuinely ours. Once the remediation contractor has completed the work and released the space, the building still needs putting back into service — fine settled dust across surfaces and ledges, floors, carpets, washrooms, corridors and common areas. That is ordinary commercial cleaning and it is what we do. It is the same arrangement we have on water damage: a restoration contractor dries and clears the space, and we handle the clean that comes afterwards.
Do you take mould enquiries from outside the GTA?
Our own cleaning work is Greater Toronto Area. For a mould referral, tell us where you are anyway — if it is somewhere we cannot help you find anyone, we will say so plainly rather than sit on your enquiry.
Is it mould or mold?
Same thing. “Mould” is the Canadian and British spelling and is what you will see on Ontario and federal government pages; “mold” is the American spelling and turns up constantly in product labelling and search results. Nobody is describing a different problem.
Related pages
Where to read things yourself
- Mould in the workplace (Canadian Centre for Occupational Health and Safety) — the size thresholds, protective equipment and work practices quoted above, in the original.
- Asbestos in the workplace (Ontario Ministry of Labour) — the Type 1/2/3 classification, training and notification requirements that apply if remediation means opening up an older building.
General information for people running commercial buildings, not advice about a specific building. Zusashi Maintenance does not perform, assess or test for mould remediation — we introduce you to a contractor, and the work and the contract are between you and them.
