February sits at the peak of the Northern Rivers wet season, and it’s also the anniversary month of the 2022 floods that reshaped how much of the region thinks about moisture and mould. Between the two, it’s a sensible point in the year to run a deliberate mould-proofing check on your home rather than waiting for a musty smell or a ceiling stain to force the issue. This checklist covers the practical steps worth working through before and during the heaviest part of the season, and what to do differently after a significant rain event.
Quick Answer
Mould-proofing a Northern Rivers home ahead of peak wet season means checking four things: that water is being shed away from the building (roof, gutters, drainage), that moisture-generating rooms are properly exhausted (bathrooms, kitchens, laundries), that subfloor and roof void spaces have working cross-ventilation, and that indoor humidity is being actively managed rather than left to outdoor conditions. Running through this in February, before the heaviest rain of the season lands, is more effective than reacting after mould has already established.
Why February Specifically
Northern Rivers rainfall is heavily concentrated between October and April, but February is typically one of the wettest months in the cycle, with warm air temperatures that keep relative humidity elevated even between rain events. That combination, sustained high humidity plus regular saturating rain, is exactly what mould spores need to establish and spread. A home that copes reasonably well in a drier month can develop a visible mould problem within weeks once February conditions set in, particularly in bathrooms, wardrobes, and subfloor spaces that were already borderline.
Roof and Gutters
Clear gutters and downpipes. Leaf litter and debris block water flow, causing overflow that runs down external walls and can find its way into wall cavities through render cracks or window flashings. This is one of the most common preventable causes of wall cavity mould in the region.
Check roof flashings and ridge capping. Northern Rivers storms bring wind-driven rain that tests flashings around chimneys, vents, and roof penetrations far more than a still, vertical downpour would. A flashing that’s held for years can still fail under a sideways storm.
Inspect for ponding or sagging. Any section of roof or gutter holding water after rain has stopped indicates a drainage fall problem that will only get worse as the wet season progresses.
Windows, Doors, and Wall Penetrations
Check window and door seals. Failed seals around older aluminium or timber-framed windows let wind-driven rain track down inside wall cavities, well behind what’s visible from either side of the wall.
Look at external render and joints. Hairline cracks in render, or gaps around pipe and cable penetrations through external walls, are common entry points for moisture that ends up inside a wall cavity rather than on the surface where it can dry.
Confirm weep holes are clear. Brick veneer homes rely on weep holes at the base of the wall cavity to let incidental moisture drain out. Weep holes blocked by garden beds, mulch, or paint are a frequently overlooked cause of slow-building wall cavity mould.
Bathroom, Kitchen, and Laundry Ventilation
Confirm exhaust fans vent outside, not into the roof void. An internally-ducted fan actively moves bathroom moisture into the ceiling space instead of removing it, and this is one of the most common drivers of both bathroom and roof void mould in older Northern Rivers homes.
Run fans during and after use. During and for at least twenty minutes after a shower is the practical minimum. A timer switch is a low-cost upgrade that removes reliance on remembering to switch the fan off manually.
Check the kitchen range hood is ducted, not recirculating. A recirculating hood filters grease and odour but returns the moisture from cooking straight back into the kitchen air.
Subfloor and Roof Void
Check subfloor vents are unobstructed. Garden beds, stored items, and overgrown vegetation against the base of the house commonly block subfloor vents without anyone noticing until a musty smell develops.
Look for standing water or persistent damp ground under the house. In a floodplain or low-lying property, this can indicate a drainage problem worth addressing before the wettest part of the season arrives, rather than after.
Check roof void ventilation. Ridge and eave vents that have been painted over, blocked by insulation, or covered during a previous renovation reduce airflow through the roof space and increase condensation risk on the underside of the roof sheeting.
Humidity Management Indoors
Get a hygrometer if you don’t already have one. A basic digital hygrometer costs under $30 and gives you an actual number to work with rather than a guess about whether a room feels humid.
Target 60 percent relative humidity or below. Above that threshold for sustained periods is when mould spores reliably germinate and spread. Our guide to humidity control in Northern Rivers homes covers dehumidifier selection, placement, and mechanical ventilation options in more detail.
Keep air moving in low-airflow rooms. Wardrobes, spare rooms, and any space that’s regularly closed up benefit from occasional airing on drier days and from avoiding items being stored flush against external walls.
After a Significant Rain Event
Check ceilings and walls for new staining within 24 to 48 hours, particularly after a storm with strong wind-driven rain. Catching a new leak early, before it’s had weeks to soak into plasterboard or framing, makes a meaningful difference to whether surface treatment is enough or removal becomes necessary.
Ventilate any area that got wet as soon as it’s safe to do so. Fans, opened windows on the next dry day, and a dehumidifier if one is available all help affected materials dry out before mould has a chance to establish.
If your property has flood history, don’t assume a repeat clean is sufficient. Where a wall cavity or subfloor space took on water again, even briefly, previous remediation doesn’t automatically mean the area is protected this time. Our region’s building stock, particularly in Lismore and the surrounding flood-affected suburbs, carries this risk more than most. Our guide to why subtropical Northern Rivers homes struggle with mould covers the underlying climate and construction factors in more depth.
When to Call in a Professional Inspection
A DIY checklist reduces risk but doesn’t replace a proper assessment where any of the following apply: a musty smell without an obvious visible source, a property with flood history that hasn’t had a dedicated moisture check since, recurring mould in the same spot despite cleaning, or a pre-purchase situation where you need documented, objective findings rather than a visual guess. A professional mould inspection uses moisture meters, thermal imaging, and air sampling where indicated to establish what’s actually happening rather than what’s merely visible.
Frequently Asked Questions
Is February really worse for mould than other wet season months?
It’s consistently one of the wettest and most humid months in the Northern Rivers annual cycle, and the combination of sustained rainfall with warm temperatures makes it a particularly active period for mould growth. That said, the underlying risk factors, poor ventilation, blocked drainage, ageing seals, are present across the whole wet season; February is simply when they tend to show up fastest.
How often should I run through this checklist?
Once at the start of the wet season, typically in October, and again in February when conditions peak, is a reasonable minimum for most Northern Rivers homes. Properties with known drainage, ventilation, or flood-history issues benefit from checking more frequently.
I’ve done everything on this checklist and still have a recurring mould patch. What now?
A checklist addresses the common, visible risk factors, but a recurring patch despite reasonable prevention often points to something not visible from a walk-through: a wall cavity issue, a subfloor moisture source, or a roof leak that hasn’t been traced yet. At that point, a professional inspection is the appropriate next step rather than continuing to treat the surface.
Does running air conditioning help during the wet season?
Yes, refrigerant-based air conditioning removes moisture from the air as part of the cooling process, making it one of the more effective tools for humidity control during humid months. Keep the unit serviced and its condensate drain clear, a blocked drain can itself become a localised mould source.