A tenant emails on a Monday about dark spotting along the stairwell wall, and by Wednesday two more people have mentioned it. The instinct is to send someone in with a bucket, and sometimes that’s the right call. But commercial mould removal that skips the question of where the water came from buys you a few weeks before the same patch returns, usually in the same shape. The first week is for working out what you’re dealing with: what to look at, what to write down, and how to tell a cleaning job from a repair job.
Why mould turns up in commercial buildings
Mould needs moisture, something to grow on, and air that doesn’t move. Sydney supplies the moisture for most of the year, between humid summers and long wet stretches through winter. The food source is already in the building, in paint, plasterboard paper and the dust sitting on a cold concrete wall, so the two things you can change are water and ventilation.
The water nearly always comes from a short list:
- a blocked gutter or downpipe pushing water back into the wall
- a bathroom or kitchen waste pipe weeping behind tiles, often for months
- an air conditioning drain pan or condensate line that has backed up
- cold surfaces in a stair core or basement car park where warm damp air condenses
- an exhaust fan venting into the ceiling cavity rather than outside
Fire stairs and car parks are the usual suspects because nobody spends time in them. Unlike a home, where someone notices a damp smell the same evening, a stairwell gets reported once the wall has already gone black.
What to check before anyone cleans
Find the water before you find a cleaner. Walk the area after rain if you can, and look directly above and behind the affected surface. Mould on a wall at head height often starts at a roof or a pipe two floors up.
Touch the lining. Press the plasterboard near the stain and at the skirting. If it’s soft, dimpled or swollen, water has been sitting there long enough that cleaning the face of it won’t help.
Check the air, not just the surface. Look at whether the exhaust fans actually run, whether stairwell vents are painted shut, and whether a tenant has sealed a window vent against street noise. In basements, a dead corner with no air movement will grow mould again even after a thorough clean.
Photograph everything with a date. Photos of the extent, the ceiling above, the unit number on the door and the gutter line give you a record that holds up later with an owners corporation, an insurer or a tenant.
When commercial mould removal is a clean and when it’s a repair
Surface growth on painted masonry, tiles, render or a concrete soffit, brought on by a humid run of weather, is a cleaning job. Treatment of the surface, better airflow, then a re-inspection a month later will usually settle it. That’s the common case in stairwells and car parks, and it’s the one most sites deal with every year.
Cleaning is the wrong first move when the lining is wet, when staining has come back within weeks of the last clean, when the carpet or underlay smells, or when occupants are noticing the issue from a distance. In those cases the repair comes first, because scrubbing a surface that’s being fed from behind just resets the clock. Removal work also generates material, and mouldy plasterboard, ceiling tiles and underlay need to be bagged, carried out through occupied areas and taken off site and disposed of without spreading spores through the rest of the building.
Damp buildings are a problem for people with asthma and allergies, and you have duties as a PCBU to manage risks to workers and visitors. SafeWork NSW sets out how those duties work in practice. For a facilities manager, the practical version is simple: act on the report, record what you did, and don’t let a known damp area sit through another wet month.
What commercial mould removal should leave behind on paper
A contractor who cleans a stairwell and sends an invoice has given you half of what you need. The other half is a record you can hand to a strata committee, an insurer, an auditor or the next manager in your job.
Ask the team to provide dated photos before and after, with the location noted in a way someone else can find. Ask what was found behind any lining that came off, because that’s the evidence of cause. Ask what method and product were used on which surfaces, what materials were removed, and what the contractor thinks the source is. Then ask for a re-inspection date, and put it in your calendar rather than theirs.
A professional report doesn’t need to be long, but it does need to turn one visit into a decision. If the same wall is clean at the eight-week check, the cause was seasonal and ventilation did the work. If it isn’t, you have a defect, and a dated history makes that a much easier conversation with the owners.
Questions to ask before you book commercial mould removal
- Will you tell me what’s causing it, or only clean what you can see?
- Who does the repair if a pipe or flashing is involved, and do I need a second contractor?
- What do I get in writing afterwards, and does it include photos?
- Can the work run out of hours so the stairwell or car park stays usable?
How to check a contractor’s client experience
Online reviews on a cleaning service rarely tell you much about damp. Ask instead for two managers on comparable sites, then ring them and ask one question: did the mould come back the following winter? A contractor with real commercial experience will hand over the numbers without hesitating, because repeat work on the same site is the thing they’re judged on too.
Frequently asked questions
Within the first week, but check the cause before the clean. A few days spent finding the leak is better value than a same-day scrub that you repeat every six weeks.
No, not reliably. Household bleach lifts the colour from the surface while leaving growth in porous render or plasterboard, which is why the stain reappears looking much the same.
Cleaning treats the surface; remediation removes affected material and fixes the moisture source. You need the second one when the lining is wet, damaged, or the growth keeps returning.
Fix the water and the mould stops coming back
If you do one thing this week, go and look at what’s directly above the patch after the next rain. On most Sydney sites the answer is up there, in a gutter, a flashing or a condensate line, and once it’s dealt with the cleaning holds.
Star Property Maintenance has been working across Sydney sites since 2002, which is more than twenty years of stairwells, car parks and plant rooms through wet winters. We clean what can be cleaned, and we tell you plainly when the cause needs fixing first.
If a patch in one of your buildings has already come back more than once, send through the photos and the dates and we’ll take a look with you. Get a free quote.
