10 ways to avoid mould/water damaged buildings when hunting for a property

Keen to avoid mould/water damage in your next rental or purchase? While it’s not entirely possible short of inviting a mould technician, building biologist and remediator to the inspection to absolutely guarantee that you’re going to be mould-free, there ARE a few signs something isn’t quite right. Naturally, you have more time on your side if you’re considering buying, but that’s absolutely not to say there aren’t some quick visual/smell cues you can’t look out for as a renter.

Being someone hit by mould illness myself –  (more on this here where I chronicle my entire story) I understand the importance of spotting these homes early, now, instead of living in one for a year and another for 8 years before realising the damage that a water-damaged building can cause to someone’s health! I’ve put together 10 things to look for when renting a house so you can work to minimise the chance of exposure to mould through a water-damaged building. 

But first, what is mould?

Mould is part of a group of very common organisms called fungi, including mushrooms and yeast. It is virtually everywhere, indoors and outdoors, but thrives in damp areas and water-damaged homes lacking adequate ventilation, including walls/ wallpaper, ceilings, bathroom tiles, carpets (especially those with jute backing), insulation material and wood. There are different species, and over time, science has discovered that the different types can impact us in different ways, from allergies to neurotoxicity to infection to carcinogenic impact. If you’re familiar with the basics on gut health and knowing that some pathogens exist happily in the gut and can even be useful in small colony size, but it’s when they proliferate and take over from the ‘good guys’ that they cause havoc, it’s essentially the same with mould. At very low levels they’re part of a healthy functioning ecosystem, but allowed to proliferate, they can cause havoc on allergies, and set off a chronic inflammatory response from the mycotoxin exposure that dysregulates both the immune and the nervous systems. It is the opposite of a walk in the park to go through. 

Why should we be avoiding mould and water damage?

Water damage and dampness occur in buildings when a pipe or roof is leaking and/or a building has not been built with the correct ‘wet area’ foundations to enable optimal ventilation and drying. Or maybe it’s an old place and the waterproofing at the base has broken down and rising damp is kicking in. Recurrent water dripping or leaking in one place results in an excessively damp area, often hidden behind the paint, foundational walls, under furniture or in nooks and crannies of a building. If you’re fortunate – or unfortunate – enough to discover the actual site, it can be a pretty shocking and menacing-looking thing, and for our health, it often is. 

Once this icky toxic mould is growing it produces tiny particles called spores. Spores are carried through the air and may cause health problems if inhaled by people who are sensitive or allergic to them. Common symptoms look like an unexplained running or blocked nose, irritation of the eyes and skin and sometimes wheezing. If you’re one of the unlucky folk who is highly susceptible to mould illness, your symptoms might be far more severe, like a racing heart, diarrhoea, nervous system issues, electric shock, migraines, mood swings, depression, joint and muscle aches and twitching and chronic unexplained illness… just to name a few. While it only seems to be about a quarter of the population that is affected, it is said by leading doctors such as Dr Ann Shippy who I had on the podcast discussing mould, that it affects the whole population to varying degrees depending on individual factors. You might also want to listen to the show I did with Dr Sandeep Gupta on mould and CIRS (chronic inflammatory response syndrome)  

10 things to look for when renting a house 

So now that you have a general understanding of why landing a good home is important, here are 10 key signs you want to look for when inspecting your next rental or potential home purchase. I should also add that if you live in a humid climate, mould prevention through keeping indoor humidity low is very important, too. I did a solo podcast on that very thing here. Getting a climate gauge is one of the best things you can do to monitor and know, and then back it up with a dehumidifier to reduce humidity. You have 10% off with AusClimate if you need either for your home. CODE: LOWTOXLIFE.

1. Visible mould. Seems obvious but it’s definitely the first red flag – if mould is visible, then chances are there’s far more hidden under the surface. Look behind cupboards, shine your phone torch into air vents/air conditioners, curtains (back and front) and blinds, in the corners of rooms, in built-in wardrobes, around edges of the bathroom, under the sink, behind couches, on widows and along window frames. Leave no stone unturned! Mould can be black, green, brown, white or furry spots. 

Image result for mould

2. Broken pipes and downpipes around the building, under the sink or in the laundry area/bathroom/kitchen areas.  While you can’t see pipes behind walls, there is the opportunity to assess the health of visible ones on an inspection. The most common offender of these is plastic water supply lines to sinks and toilets, which newer buildings tend to use more. (Tip: Copper, which older buildings tend to use, almost never leaks. Galvanized steel is another sturdy material in this regard.)

3. Mildew (a surface fungus) is typically a grey or white colour – that can become black as the fungus grows. It’s commonly found in bathrooms and laundry areas as a result of poor ventilation.

4. Condensation, much like mildew, is an indicator of dampness. It looks like water running down walls, windows, or laundry surfaces. Condensation equals poor ventilation and means the building isn’t “breathing” properly. You’re left with a significantly increased chance of a damp indoor environment, especially if you’re going to be unable to leave windows open for long periods of time due to either weather or security.

5. Peeling or bubbling paint on walls. This commonly occurs as moisture is seeping between the hard wall surface and the paint. If you see this, it’s a cause for concern and definitely an indication that there is either rising damp or a broken pip leaking behind the wall – check the walls on the other side of any bathrooms or laundry for this. Typically the area above or below the paint will have a leak. 

6. A musty smell. Most moulds have a pungent, musty odour. If there is a strong smell in the rental property, this indicates that there is likely mould present, coupled with poor ventilation and dampness in the room. Go into the wardrobes and built-in drawers and have a good sniff around. If there is synthetically perfumed clothing in the wardrobe that could mask your mould detective nose, then remove a drawer from the built-ins and sniff behind there (or get someone who isn’t prone to becoming ill to do so – My husband is our sniffer dog these days!) 

7. You experience allergy-like symptoms or a pounding heart or – I know it might sound weird – a tense tongue. A good indicator is your body’s physical response when you enter a room. If you have sinus issues, coughing, wheezing, a tight chest, asthma triggers, irritated eyes, metallic taste, shortness of breath or a racing heart – to name a few, then this is a sure-fire sign that this is not the home for you. Be calm, take a few deep breaths if you can so that you rule out any fear and anxiety being the culprit, and if you tune in and feel these symptoms without a shadow of a doubt, then walk on out and into the next inspection. 

8. Water stains on the exterior. If you notice that the exterior of the building has water patches or stains dripping down the wall, look for the root cause and question the real estate to find the source. Sometimes it’s just from rain or another tenant but if it’s a continuous dripping stream of water this is the ideal home for mould and damp to grow (especially if you live in a humid city). Avoid!

9. Moss growing on outdoor or porous surfaces. If you can see visible moss growing from brickwork, this may not indicate that the building has a leak, but it definitely highlights that the house is in a damp location. Be very discerning here – if the home feels musty inside too then you get a double no – run! Image result for moss on buildings

10. Poor drainage. Check the gutters around the property – are they clogged, dirty or mouldy. Clogged gutters mean drainage is not adequate and a cause for concern. If they can be cleared out you might be ok, however, if the overall state of the rental or home is not in good condition, don’t commit to it.  It’s a sign that the upkeep is poor and not prioritised, and you’ll face uphill challenges asking for things that aren’t in good condition to be attended to. 

Another bonus trick I’ve employed when searching for a new mould-free home is to avoid any apartments or houses that are at the base of a large hill, or in a part of a suburb that is shaped like the base of a valley with hills coming up from the area from all sides. Homes on slopes tend to be bigger traps for foundation issues and rising damp and/or homes that are shadowed in large bushland/trees overhead. Typically these types of places experience higher levels of water runoff in storm periods, allowing for a greater chance of pooling water and water damage to occur. I’m now living in a location that is raised from the ground, free of tropical-humidity-trapping trees and less susceptible to the weather with good guttering and drainage. It can be done! 

Aside from the visual cues you can look for at inspections, I highly recommend you arm yourself with some tools that you can take to do your own sneaky analysis when the real estate agent isn’t looking! 

I use the Hygrometer for testing humidity in the air space and the moisture meter for testing damp in walls. Both will give you a near-instant answer if you’re still unsure about a place. When we moved to one apartment years ago, hilariously my husband distracted the agent talking cars in the living room, while I went on a full Mission Impossible inspection of the rooms. 

If you want to hear about my mould story you can listen to this podcast where I talk through the whole experience of moving from a water-damaged building a couple of years ago and how/what we cleaned and what we had to get rid of, sadly. There’s also my big aggregated post “So You Think You’ve got Mould” with lo9ts of resources and links.


If you’ve struggled with mould illness you might like to check out my course, Inflammation Ninja that I developed as a result of experiencing chronic inflammation after mould exposure which has now helped hundreds of people who have lived with many different types of inflammatory conditions and illnesses. I know the feeling of feeling like it’s not possible that it will ever get better and everything hurts and there are scary symptoms in the mix. I also know the debilitating cost of testing and scanning everything and bouncing around on a million protocols, supplements and even trying medications because, hey, I’m open to anything that will move the needle for someone in SOS mode – I just don’t think finding answers and a path forward should be expensive for people. This was a huge part of my motivation in creating this one. If it’s found you at the right time then, yay! xx

Has this list helped? I’d love for you to share your experience of trying to find your perfect safe home below! 

If you’re buying a house and there’s one you’re really serious about? I’d test it with a Mould Technician or Building Biologist – get them to take a couple of samples – a mix of dust/air/swap in any room you’re not sure about, and test, don’t guess!

Low Tox. Healthy People. Happy Planet


Comments 9

  1. Thanks for this checklist Alexx, it’s really helpful! We are living in a house that gets condensation on the windows and internal plantation shutters in winter, we try to open the windows for ventilation each day. But, do you also recommend using a dehumidifier or one of those moisture absorbing tubs?

    1. Post
  2. Hey Alexx – great article and recommendations.

    I had my own experience with mould-related illness and another recommendation I would add would be around airflow and ventilation. Whether the property design allows for natural crossflow (e.g. air able to move east to west, north to south through the house) and new air coming in can be really important.

    A lot of newer build apartments and duplexes only have windows on one or two sides, which reduces the capacity for ventilation and can create environments more conducive to mould. It’s definitely something to consider for ground level apartments in particular.

    1. Post

      Yes, absolutely Shannon. I have just shared a series on social media about this. New builds aren’t all that great! Hope you are feeling better.

  3. Hi Alexx great article. Do you have any recommendations on living with Mould. Other then increase ventilation if possible? I am renting and unfortunately it’s the only place we can get at this point in time. There a visible signs of mould and our bedroom/ensuite takes most of the day to dry out after having the aircon at night. I have just learnt about dehumidifiers which I am purchasing one on the weekend.
    Do you recommend an air purifier? Do you think would assist?
    Any advice is appreciated, thank you.

  4. I can totally relate to this. I have all kinds of tools for detecting mold but it’s not practical to show up to an apartment looking like a ghostbuster, people will just think your fucking nuts. I wanted to add a few more tips from my own experience, this a California perspective:

    1. Black ring in the toilet. Although this can happen naturally after a toilet sits for weeks on end it shouldn’t be something that happens within days of normal use. If you find yourself constantly cleaning the ring it means there are either a lot of spores in the air or there is a lot of glucose in your urine.

    2. Stucco patching. If you see patches of stucco that are large it’s likely been repaired due to water damage. Sometimes you see this around windows where improper flashing likely caused water intrusion. Unfortunately the repair is usually done by a handyman and doesn’t get rid of the actual mold in the wall. So spot patches on stucco can be a huge red flag, line patches less so. In all honesty it’s better to avoid stucco all together, too many opportunities for mistakes. Unfortunately stucco is extremely popular because it’s cheap. In LA it’s something like 7 out of 10 places have a moisture issue, some of course are worse than others.

    3. Flat roofs. Although flat roofs have the ability to divert water, they also tend to collect water as the surface is often uneven. It doesn’t guarantee water damage but it’s a definite risk over the traditional roof.

    4. Cockroaches. They love to nest in moist places like decaying particle board etc., if you see them chances are there is atleast some form of moisture issue. Put it this way I haven’t lived at a single place personally that didn’t have both cockroaches and mold. I’m sure a place can exist without both but I’m convinced the odds are high that if you have one than the other isn’t far behind.

    5. Newer buildings, its estimated something like 70% of newer buildings (California) will fail from water damage within the first 5 years due to cheap materials and labor coupled with a tight building envelope to ensure energy efficiency, this creates the perfect storm for mold to form. Due to tight deadlines on contractors and an emphasis on ROI, it doesn’t take much for that $3000 luxury condo to have a random improperly installed plastic pipe burst and start a swamp in the walls. Of course management will fix the wall but they won’t properly remediate it. Hidden mold is the worst.

    6. Dust sampling. Although not very cost effective, for about $100 a pop on Amazon you can swab some dust from your prospective place fairly incognito (take a tape measure and a notebook with you as a distraction) and send it in to find out the relative mold index within a fairly reasonable amount of time. It’s expensive but far cheaper than the ERMI/HERTSMI test which are just as great and super reliable. This IMO is one of the best ways to truly know, it’s not perfect but it’s practical and it’s cheaper than moving into a place that will make you feel worse than you already do.

  5. Hi Alex, I want to thank you for all this amazing info you share- I’ve been learning a lot from your website and podcasts.
    we have lived in a house for the last 3 years and I have been getting sicker and sicker. A natural path has suggested that mould might be the issue. We are planning to move, as the house is built on the soil and although lifted in areas – some areas are very close to the soil and I do not think there’s enough ventilation. My question is regarding our current furniture etc. I’m not sure if in this case we will have to get rid of 4eg our beautiful wool rug (I smell mould on this) and the couch. Or if a good clean (I will probably have to get carpet cleaners in) would do the trick? I’m a bit confused between what would be considered toxic mould build up and others where you could treat with conqurium, 4eg)

    1. Post

      You’re very welcome Gea. ,I know we’ve spoken via email. Wishing you luck on the journey and strength through the very boring and often tough mould maze! Alexx x

      1. I would love to know the answers to this too! I am currently living with hidden mould (toilet and shower/hallway walls) and probably under my sons carpet… We all have mould allergies and possibly CIRS for me…all reacting with snotty noses, I have constant inflammation, etc etc. This is all from a house we left back in 2019 due to lots of hidden mould. We are in a rental now for 2.5yrs and have unfortunately just realised there is mould due to our reactions and have already been searching for a rental for over 6 months with no luck. I don’t know how bad the mould is and whether we are the point where we have to ditch all our belongings again. The last time was so traumatic for my daughter, she has had mental health issues since. Is there a way to test your furniture and belongings?

Leave a Reply

Your email address will not be published. Required fields are marked *