Waterproofing Bathrooms and Shower Areas

While it is generally understood that it is necessary to thoroughly waterproof a wetroom – the situation regarding bathrooms is less clear. In this article we discuss the advice as stated in British Standard BS 5385-4:2015 which advises waterproofing bathrooms and shower areas in certain circumstances. We also discuss what the advice actually means.

The British Standard makes it clear there should always be tanking in a wet room but it also prescribes using tanking and water resistant materials in domestic power showers, communal shower and swimming pool areas. Basically, any area where there is likely to be continuous contact with water (with little opportunity for the installation to dry out between use), the area behind the tiles should be made watertight by tanking.

For areas subject to occasional wetting, for instance domestic low pressure (non-power) showers the British Standard says that for water sensitive backgrounds such as Plasterboard, a waterproofing tanking system may be considered, this is obviously not compulsory, but it goes on to say that “The use of impervious grouts and adhesives is no substitute for a tanked installation” In other words if you want to be sure that your bathroom will not leak then the room should be tanked. This is of particular importance when you have an upstairs bathroom/shower room or when you live in a flat with others living below you.

Waterproofing Bathrooms and Shower Areas to British Standard BS


Tiled Bathrooms and Shower Areas

There can be confusion regarding what is necessary to create a waterproof bathroom, shower room or wetroom. Many tile adhesives and grout are labelled as waterproof and it is not uncommon for people to believe that, by using waterproof tile adhesive and grout, they have created a properly waterproofed room, but this is not the case. It is true that tile adhesives and grouts can withstand contact with water without significantly degrading or losing function in wet conditions, but they are not elastic materials and over time they will crack and allow water to pass through to the wall behind.

By waterproofing your room using a tanking system such as Aquaproof you create a flexible waterproof layer to contain the water within the room: preventing leakage into adjacent rooms and water sitting in the structure of the building.

In a tiled shower or bathroom area, which has not been fully waterproofed, water will often leak under the tiles, causing damage to the timbers before there are any obvious signs of a problem. When the leak finally becomes visible, typically on the ceiling of the room below, it is common to find significant damage to floor timbers and boarding. Concrete is more resilient to water but will still leak, typically through day joints or shrinkage cracks.

Vinyl Floored Bathrooms and Shower Areas

It is often considered that tanking is unnecessary when a wetroom has been floored with a safety vinyl such as Altro, as the product is strong and the seams are welded and shouldn’t leak. However increasingly, such wetrooms are being specified with a liquid applied waterproofing under the vinyl as a safeguard against problems such as mechanical damage, the top edge of the vinyl unclipping or an imperfect weld.

The problem of leakage in a bathroom situation can be much worse. The vinyl used is not usually welded and sealed and so the opportunity for water to seep under it, and leak into adjacent rooms, is higher. The cost of the waterproofing in such a situation will be minimal compared to repairing damaged timbers and collapsed ceilings. The process of waterproofing with a liquid applied membrane is straight forward and will not only increase the longevity of the bathroom but prevent expensive problems developing in the fabric of the building and adjacent rooms.


The British Standard regarding waterproofing bathrooms clearly encourages installers to place a greater emphasis on creating a robustly waterproof environment in domestic bathrooms. The advantages are clear, in terms of protecting the integrity of the bathroom and surrounding areas of the building.