Black mould Part 2 - Penetrating Damp

13th Nov 2016

Hello everyone. I’m back with the second part of my series of blogs on household mould and this time we are going to be concentrating on penetrating damp.

As I mentioned previously, penetrating damp can cause mould to appear in random places in your home and as a result; can often go undiagnosed. As water can run horizontally or vertically within walls and ceilings to follow the path with the least resistance, the place where your mould appears and the location of the water ingress may be different. As the name suggests, penetrating damp is when water penetrates your home but although it can sometimes be tricky to discover where exactly it is getting in, with penetrating damp you can resolve the issue with a simple repair. If you think you have penetrating damp, pay attention to it regularly during extended periods of bad weather as it this is likely to cause it to worsen.

For damp to penetrate your property, it has to get in from the outside. Therefore whenever you think you have penetrating damp, it would be worthwhile having a look around outside to see if you can notice anywhere the water may be getting in. Be sure to check: roof tiles for damage, guttering, roof flashings above garages/porches & around chimneys, pointing and seals around openings like doors and windows. If you notice any damage, please seek expert advice on repairs unless you are professionally trained to complete them yourself.

It’s worth noting at this point that damp you have discovered may not necessarily be coming from outside. If there are wet rooms (bathrooms, kitchens etc.) above you, there’s a chance the water may be coming from there. Again this water can travel between floors and so may not be appearing directly below the original source. If you think this may be your cause, a quick below any sinks/baths etc. above you will tell you if that is the source. If you are unsure, you can leave some newspaper below where you think the water may be coming from. Check the paper from time to time and you will quickly establish if it is getting wet.  

If you think you have penetrating damp but you have searched and cannot find an obvious cause, you can get your property surveyed to establish the cause. There are numerous companies available that can carry out surveys so be sure to shop around for quotes before committing to one. I cannot stress the importance of completing this quickly enough as if left untreated, penetrating damp can cause much bigger problems in your home and will end up costing a lot more in repairs in the long run. 

Once you have discovered and repaired the cause, you still have to ventilate your home to remove the moisture that is already inside. The easiest way to do this is to invest in a dehumidifier which will draw out the moisture. You can also dry out the inside by switching your heating on although make sure to keep your rooms well vented while doing this or you may cause condensation to form (which we’ll discuss in more detail later.) One final point I’ll make on venting your property is the moisture contained within it can take weeks or even months to dry out. If you have your repairs completed and a few weeks later you are still getting moisture building up in your dehumidifier it doesn’t necessarily mean you still have penetrating damp. It can take a while for the water to be drawn out depending on how long the problem has been ongoing so don’t assume you still have a problem if the mould/water marks don’t disappear instantly once the works are complete.

I hope if you’ve had a problem with mould forming in random places, this blog has helped you to discover the source and subsequently fix the problem. If you have mould growing in your property and have checked externally and can’t see any obvious damage, it may be your mould problem is being caused by condensation. If that’s the case keep your eye on the site for my next blog which will examine condensation, what you are doing to exacerbate your problem and what small changes you can make to resolve it and make your mould disappear for good.

As always, I welcome all questions & comments relating to my blogs so please don’t hesitate to get in touch if you have either. You can contact me on or via any of our social media platforms to share your views.