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How to avoid mould in joints.

Portrait Peter Brandecker Ramsauer
From Peter Brandecker
Abstract visualisation of a mould spore

Unsightly edges in the corners and joints of tiles? Especially in bathrooms, moisture, organic residues and heat offer mould spores optimal conditions to spread. With the right choice of sealant and a few helpful tips, mould can be eliminated.

Modern bathroom with green tiles, large round mirror and bathroom cabinet with wooden front.

Avoid mould in the bathroom by using the right joint

The basic prerequisite for preventing mould in bathrooms is an intact, waterproof and clean joint. This is because the combination of dirt and moisture provides an ideal breeding ground for the growth of mould spores. In order to ensure that residues can be properly removed, you should use abrasion-resistant silicone than can be easily smoothed for perimeter joints of bathtubs and shower trays. When sealing joints, make sure that the surface is smooth so that water can run off. Fungicidal and bactericidal agents in the sealant have an anti-fungal effect and can thus delay mould growth over a long period of time. 

Fungicidal and bactericidal sealants:

125 Handwerk
Neutral – oxime
color-circle 18 colours
3 sizes
450 Sanitär
Acetic acid/acetate
color-circle 68 colours
2 sizes
445 Stein + Sanitär
color-circle 11 colours
520 Weather Flex
Silicone marine sealant
color-circle 3 colours
440 Naturstein
color-circle 39 colours
2 sizes

Removing joint mould

For mould to develop, the spores must find substances that they can use as nutrients. In most cases, it is not the sealant itself that moulds but dirt residues such as soap residues or dust. This is called primary infestation. In combination with moisture, this results in the formation of mould, which becomes visible as black or yellow spots. If you discover such discolourations in your bathroom, the mould can usually still be removed using cleaning agents containing chlorine.

The abstract illustration shows two different stages of mould infestation. Primary mould, where the joint is untouched by the mould spores, and secondary mould, where the mould spores merge with the joint.
Primary infestation (left) compared to secondary infestation (right).

Once the mould has bonded with the sealant, this is called secondary infestation. The only solution in this situation is to remove the joint together with the mould. To do this, you can cut the silicone out of the joint using a cutter knife or remove it using a special agent. Before reapplying the sealant, the entire area around the adhesion surface needs to be disinfected. Always apply the new seal with a fungicidal sealant.

Portrait Peter Brandecker Ramsauer
From Peter Brandecker