NHBC Technical Guidance 9.2/06: Tiling Showers and Bathrooms

Have you heard about the new NHBC Technical Guidance 9.2/06 (Nov24)?

The revised NHBC guidance finally comes into force on 1st January 2025. Read on to find out what this means and how it effects you.

NHBC Technical Guidance Diagrams of area to be tanked

NHBC Technical Guidance for tiling shower areas, bathrooms and bathroom pods

NHBC’s revised guidance looks at substrates for the tiling of bath and shower enclosures, wetrooms and bathroom pods. In this article we show you what these changes mean to your business. We highlight the changes to the guidelines – which areas they apply to, and when they come into effect. We also talk you through the issues in waterproofing design that have led to these amendments. After you have read this article you can click on the link to see the full NHBC Guidelines.

Who will the NHBC guidelines apply to and how will this impact design and application?

You need to abide by this guidance for every NHBC registered home whose foundations are begun on or after 1st January 2025. This applies even if you are using offsite manufactured bathroom pods. After the 1^st January 2025 deadline, you are required to take special waterproofing precautions for all rooms covered within the document “Technical Guidance 9.2/06 (Nov. 24). This includes tiled areas around baths, shower enclosures and wetrooms.

For lower pressure showers with less than 12 litres per minute throughput, the required standard is lower than for power showers and wetrooms. For these “lower risk” areas there is now an option to use waterproof tile adhesive and grout, without a specialist tanking. However, there are some extra conditions to this: You must use a water resistant substrate (backing board). Also the perimeter of the bath or shower must have a preformed or adhered up-stand that sits behind the tiling. As an alternative to these special measures, an approved tanking system can be used.

If you are installing any wetroom, or are using a shower with a flow rate of 12 Litres a minute or greater, then a full tanking system is required.

House builders must waterproof these sensitive areas with an approved tanking system. When you use a liquid applied system this must conform to “EAD 030352-00-0503 for liquid applied waterproofing”.

Why use the Aquaproof System?

The great news is that Koster Aquatecnic have you covered. Our market leading, CE marked Aquaproof System has been used in the UK and Ireland since 2000 and has been independently tested to the ETAG and EAD standard since 2018. We can provide you with in-depth technical support, either over the phone or on-site for larger projects.

Ensure you are using the correct products

Where a tanking system is required the installer can’t just use any product that claims to meet some (or all) of the tests in the EAD. You must check that any testing is independently verified. The Aquaproof System is tested by the DIBt (Deutsches Institut fur Bautechnic) and has been issued with it’s own ETA (European Technical Approval) ETA-09/0200. Koster Aquatecnic are based in the uk and are currently the only UK producer with this approval. With our technical certification and unrivalled technical support, Koster Aquatecnic can help on your next project, be it a housing estate or an individual wetroom.

Why have the NHBC Guidelines been amended?

New home insurers have seen a rise in claims relating to the walls surrounding baths, shower enclosures and bathroom pods. This is often the result of insufficient waterproofing of these areas. People often use waterproof tile adhesives instead of a certified tanking system. This is a mistake in the understanding of what a waterproof tile adhesive actually does. When you see the term “waterproof” on a bucket of tile adhesive, this means the tile adhesive itself is resistant to water and will not break down with regular exposure. However, a “waterproof tile adhesive” does not form a waterproof membrane and will not protect your walls from water ingress over time.

In the initial version of their guidance, NHBC said that a tanking system must be used around all baths and shower enclosures. The November 2024 update considerably waters down this requirement and now tanking is only mandatory for wetrooms and power showers. We believe this late change to be a result of pressure from large national house builders. The latest edition now makes little sense, as a “standard shower” dispensing unto 12 litres a minute still produces a very high water pressure and will soak all of the walls around the shower.

British Standard BS 5385 – 4:2015 recommends that for water sensitive backgrounds e.g. gypsum plaster, additional protection in the form of a waterproofing tanking system may be considered. It also states that “The use of impervious grouts and adhesives is no substitute for a tanked installation”. Koster Aquatecnic can only recommend that this advice is followed, we have seen so many failed shower areas over the last 24 years, where no tanking was used. If you want to make sure that you shower area is secure, then full tanking is a very cost effective procedure, which gives added peace of mind.

The purpose of NHBC’s new Technical Guidance Note was to clarify their position on appropriate substrates for tiling in domestic bath and shower enclosures, wetrooms and bathroom pods. If anything, the latest edition creates more uncertainty, and it will once again be down to each individual house builder as to whether they tank all showers or just use waterproof tile adhesive. If your project is not being insured by NHBC, then you may need to check the requirements of other new home insurers. It seems likely that most organisations will follow the NHBC lead on this. To a large extent we find that the new NHBC guidance re-enforces the recommendations given in BS 5385-4:2015, but stops short of clearly recommending tanking for what they consider to be the “lower risk” areas. This British Standard has been largely ignored by house builders over the last 9 years, but at least the new NHBC technical guidelines shine a spotlight on the subject and have opened up a discussion. In time, the hope is, that this will lead to even higher standards.

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