Best Ways to Waterproof a Bathroom in 2025 – Methods, Products & Regulations
If you’re tiling a bathroom or planning a wetroom, waterproofing isn’t optional anymore. Between new UK regulations and what we’ve learned from countries that do it properly, the best bathrooms are now fully tanked, not just tiled.
Why bathroom waterproofing matters more than ever
Tiles and grout are water‑resistant, not waterproof. Without a proper tanking system behind them, moisture slowly finds its way into plasterboard, timber, and screeds. The result? Swollen floors, blown plasterboard, mould, and leaks into rooms below.
Insurers and warranty providers have seen enough claims to start tightening the rules. In the UK, the NHBC now requires approved waterproofing systems in many tiled wet areas for new‑build homes covered under their warranty, especially wetrooms and higher‑flow showers. Systems must be independently tested and fall into one of three categories: liquid‑applied membranes, flexible sheet membranes, or watertight boards.
What “good” looks like in countries that do it properly
Scandinavia – fully tanked bathrooms as standard
In Sweden, Norway, and Denmark, the whole bathroom is typically treated as a wet area. Floors and lower walls are fully tanked with sheet membranes or watertight boards, and drains, corners, and penetrations are detailed as part of a tested system. The result is far fewer moisture‑related failures over the life of the building.
Central Europe & beyond
In Germany and other parts of Europe, standards such as DIN 18534 set clear requirements for waterproofing in wet areas, including classification of risk zones and mandatory membranes in showers and around baths. Similar approaches exist in Australia and New Zealand, where bathrooms are treated as “wet areas” with defined waterproofing obligations rather than just “rooms with tiles”.
The common thread: they don’t rely on tile adhesive and grout alone. They use complete, tested systems that create a continuous waterproof layer behind the tiles—or behind decorative waterproof wall boards.
Current and emerging UK requirements
In the UK, the big shift is coming via warranty providers and technical guidance rather than a single headline law. The NHBC’s updated technical guidance for tiling showers and bathrooms, which applies to NHBC‑registered homes with foundations started from 1 January 2025, requires special waterproofing measures in wet areas.
Key points from recent NHBC guidance
- Wetrooms and higher‑flow showers must be waterproofed with an approved tanking system.
- Even standard showers and shower‑over‑bath areas often require tanking if the substrate isn’t inherently water‑resistant.
- Acceptable systems include liquid‑applied membranes, flexible sheet membranes, and watertight boards that meet relevant European Assessment Documents (EADs).
The direction of travel is clear: expect more bathrooms to be treated like Scandinavian wet areas over the next few years, with full‑floor tanking and properly detailed shower zones becoming the norm rather than the exception.
The main methods of waterproofing a bathroom
There isn’t one “best” method for every job. Instead, there are three main approaches, each with strengths. The right choice depends on your substrate, layout, and installer.
Sheet membranes are thin, flexible waterproof layers supplied on a roll or as pre‑cut panels. They’re bonded to the substrate and then tiled over—or used behind decorative waterproof wall boards.
- Consistent thickness and performance across the whole area.
- Excellent for floors and lower walls in showers and wetrooms.
- Often include decoupling properties to handle minor movement.
Liquid membranes are painted or rolled onto the substrate in one or more coats, then left to cure before tiling or panel installation.
- Good for complex shapes and awkward details.
- Easy to carry and store on site.
- Performance depends heavily on correct film thickness and coverage.
Foam‑cored or cement‑faced boards that are inherently waterproof and dimensionally stable. They form both the structure and the waterproof layer when joints are taped and sealed.
- Ideal for building shower walls, niches, and bath surrounds.
- Lightweight, strong, and easy to cut.
- Often used in combination with sheet or liquid membranes on floors.
Unbiased look at market‑leading waterproofing products
Rather than pushing a single brand, it’s more useful to group products by type and highlight some of the well‑established systems that installers trust. The best choice is usually to pick one complete system and follow that manufacturer’s instructions from substrate to finished surface.
Sheet membrane systems
Best for: Floors and lower walls in showers and wetrooms, especially where you want consistent performance and minimal drying time.
- Schlüter‑KERDI: Widely used orange sheet membrane with matching drains and accessories.
- Impey WaterGuard: Self‑adhesive 1mm membrane with decoupling properties, designed to pair with Impey wetroom trays.
- Wedi Subliner / similar sheet systems: Thin membranes from board manufacturers, often used with their own drains and formers.
- Ardex SK100 or equivalent: Sheet systems from adhesive manufacturers, tested with their own tile adhesives and grouts.
Liquid tanking systems
Best for: Shower walls, niches, and complex shapes where a brush‑on solution is practical.
- Mapei Mapegum WPS / similar: Flexible liquid membrane for internal wet areas.
- Ardex S7 / S9 or equivalent: Liquid systems designed to meet European waterproofing standards when applied at the correct thickness.
- Aquaproof‑type systems: Specialist wetroom liquids tested to EAD/ETAG standards and used in commercial projects.
Waterproof boards and formers
Best for: Building the structure of the bathroom – walls, floors, benches, and tray areas – with integrated waterproofing.
- Wedi boards: Foam‑cored, cement‑faced boards and pre‑formed shower elements.
- Marmox / Jackoboard: Similar waterproof construction boards for walls, floors, and features.
- Impey AquaDec & similar tray formers: Pre‑sloped wetroom trays that work with compatible membranes and drains.
If you don’t want tiles everywhere, many of these systems are also designed to sit behind waterproof wall boards such as Wetwall, Nuance, and PVC wall panels. You still tank the critical areas, but finish the walls with large, easy‑clean panels instead of grout lines.
What we recommend in real bathrooms
For most modern bathrooms and wetrooms, especially upstairs or over sensitive areas, we lean towards a sheet membrane or waterproof board system on the floor, with either sheet or liquid tanking on the walls in and around the shower.
That might mean a wetroom tray (such as an AquaDec‑type former) with a compatible sheet membrane across the floor, waterproof boards on the walls, and a matched adhesive and grout system. Or, in some cases, a tanked wall with Wetwall, Nuance, or PVC panels as the final finish for a grout‑free, low‑maintenance bathroom.
It’s a belt‑and‑braces approach that lines up with Scandinavian practice and the direction of UK guidance.
See real waterproofing systems and wall boards in our Norwich showroom
If you’d rather see this in person than read another spec sheet, you can visit our Bubblegum Bathrooms showroom in Norwich. We can walk you through tray formers, membranes, boards, drains, and full‑size Wetwall, Nuance, and PVC panel displays, and show how they all tie together behind the tiles or panels.
- Compare different waterproofing methods side by side.
- See waterproof wall boards and tiled finishes on real displays.
- Talk through UK guidance and what it means for your project.
- Plan a bathroom or wetroom that’s built to last, not just to look good on day one.
Planning a bathroom or wetroom and want it waterproofed properly?
Bring your room sizes, photos, or plans. We’ll help you choose the right system – from tray and drain to tanking, tiles, or wall boards – so your bathroom looks great and stays dry for the long term.
Bathroom waterproofing FAQs
Strictly speaking, regulations focus on wet areas like showers and baths. But countries with the lowest failure rates treat the entire bathroom floor – and at least the lower walls – as a wet area. If you want long‑term peace of mind, full‑floor tanking is the smarter choice.
For most UK homes, a sheet membrane or waterproof board system on the floor, combined with sheet or liquid tanking on the shower walls, gives a great balance of reliability and practicality. The key is using a complete system from one manufacturer and following their instructions.
NHBC guidance directly affects new‑build homes under their warranty, but it’s also a good benchmark for best practice in renovations. Even if your project isn’t NHBC‑registered, working to those standards means your bathroom is built to modern expectations rather than old habits.
You can, but it’s not ideal. Most manufacturers test their systems as a whole – tray, drain, membrane, tapes, adhesive, and grout. Mixing brands can leave you in a grey area for performance and warranty. Wherever possible, stick to one system or get written confirmation that the combination is approved.
Some systems are DIY‑friendly, especially boards and sheet membranes with clear instructions. But for wetrooms, upstairs bathrooms, or projects where failure would be expensive, using an experienced installer is usually the better investment.
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