Black Shower Mould

Black shower mould is a frequent topic of conversation with my customers. They want reassurance that their new bathroom isn’t going to suffer from black shower mould in a few months. And I come across black shower mould in almost every bathroom I strip out prior to refitting. It can be the main reason for fitting a new bathroom as the water finds its way through the cracked and dirty grout and sealant, and onto the ceiling below, so it is well worth preventing.

It all starts with the initial installation of the shower enclosure, or cubicle, whatever you prefer to call it. In the UK, the vast majority of enclosures are glass screens and doors, framed to a greater or lesser degree with aluminium, which sit on a shower tray. The walls are most often tiled, and the whole installation is dependent on silicone sealant to keep the water in.

Modern power showers and pumped showers move large quantities of water (15 – 25 litres/min) compared with the gravity fed showers we were all quite happy with a few years ago (4-5 litres/min) and to keep this water inside the shower needs a quality tiling job, with water resistant adhesive and grouts, and high quality silicone sealant.

Before tiling a shower area, or even around a bath that has a shower over it, I “tank” the area by painting on a waterproof coating to make the walls waterproof. Follow that with a high quality adhesive and grout, and the foundation is laid for a tiling job that will last a long time.

Silicone Sealant and Black Shower Mould

The choice of silicone sealant is critical though as it stops the water from leaking underneath and around the sides of the shower enclosure. And, guess what, not all silicones are the same. Locally, in Nottingham, I can pay anywhere between £1.95 and £7.95 for a cartridge of silicone, and although you may think that price and quality go hand-in-hand, they don’t.

When choosing a silicone, first make sure that it contains a fungicide – it may be labelled “anti-mould” or “anti-fungal” but I sometimes wonder how much active anti-fungal ingredient these sealants contain. Ideally the performance related to mildew and fungus resistance will have been tested in accordance with the ISONorm 846.

More important to me is flexibility because mould can be prevented from forming by regular cleaning and drying, but flexibility is an inherent property of the cured silicone. A quality sanitary silicone, such as Dow Corning 785, will be in accordance with ISO 11600-F-20HM. This ISO standard is used to specify sealants and the key figure for me is the “20″ which means that this sealant has the capacity to absorb up to 20% movement in the joint. And when I’m trying to keep large quantities of water inside a modern shower, I want a sealant that is going to to cope with a bit of movement easily. Many of the cheaper silicone sealants only have 12.5% or even 7.5% movement capability, and I guess that’s why they cost ony £1.95 or less.

I’ve digressed a bit from avoiding mouldy showers but I think it’s important to understand the technical side so that if you are replacing sealant in your shower you know what to look out for, and also to try and make sure that your bathroom fitter is using a high quality sealant that will last. Personally, I always use the higher quality, flexible, mould resistant sealants for my customers. High quality sealants are one of the most important materials and have a minimal effect on the price of a new bathroom.

Cleaning and Black Shower Mould

But having said all this about installation and specifications, there is no avoiding the fact that to keep a shower area clean and free from mould it needs cleaning regularly and good ventilation. However good the sealant is, if the atmosphere is really damp and water is allowed to stand on the surface it will, sooner or later, start to go mouldy. I have seen showers installed at least ten years ago which are still virtually “mould free” because;

  • After every shower the surfaces are wiped over to remove any standing water
  • Weekly, or thereabouts, surfaces are cleaned and dried
  • The shower door is left open to allow air to circulate inside the shower enclosure
  • The extractor fan is used, or ideally the window is opened for a few minutes after every shower.

I’ve also seen showers that are left soaking wet all day every day with the door and window closed, and the mould is starting to form within months. It’s soul destroying when I’ve left somebody with a spotless bathroom and if I happen to call back later on a new enquiry, to see that the bathroom is suffering with black shower mould because surfaces are often left wet.

It may be a chore to wipe over the shower every morning when you’re late for work, but believe me, it will be well worth it, helping to keep your bathroom free from black shower mould for many years to come!