A comprehensive guide to waterproofing a shower room in the UK — covering tanking methods, membrane systems, building regulations, and step-by-step best practice for both homeowners and professional installers.

Introduction

Waterproofing a shower room is one of the most critical stages of any bathroom installation. Get it wrong and you risk structural water damage, mould, rot, and costly remedial work. Get it right and your wetroom will perform flawlessly for decades.

This guide covers everything you need to know — from the relevant UK building regulations and British Standards, to choosing the right waterproofing system and installing it correctly. Whether you're a homeowner tackling a renovation or a professional installer, this is your definitive reference.

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UK Building Regulations & Legislation

Waterproofing a shower room in the UK is governed by several pieces of legislation and guidance. Understanding these is essential before any work begins.

Building Regulations Approved Document C – Site Preparation and Resistance to Contaminants and Moisture

Approved Document C of the Building Regulations requires that floors and walls of rooms containing a bath or shower must resist the passage of moisture to other parts of the building. This is the primary legislative basis for tanking and waterproofing in wet areas.

Building Regulations Approved Document A – Structure

Where a wetroom floor former is installed into a timber floor, the structural integrity of the floor must be maintained. Approved Document A requires that any notching or cutting of joists is carried out within permitted limits, and that the floor remains capable of supporting the required loads.

BS 8000-0:2014 – Workmanship on Building Sites

This British Standard sets out the general principles for workmanship on building sites, including the installation of waterproofing systems. Compliance with this standard is considered best practice and may be required by warranty providers.

BS EN 14891:2012 – Liquid Applied Waterproofing Products

This European Standard specifies the performance requirements for liquid-applied waterproofing membranes used in wet areas, including shower rooms. Products such as the Impey WaterGuard membrane are designed to exceed these requirements.

Part P – Electrical Safety

If your shower room installation involves any electrical work (such as electric showers, underfloor heating, or extractor fans), this must comply with Part P of the Building Regulations. Work in bathroom zones must be carried out by a Part P registered electrician or notified to your local building control authority.

Party Wall Act 1996

If your shower room is adjacent to a neighbouring property (e.g. in a semi-detached or terraced house), you may need to notify your neighbour under the Party Wall Act before carrying out structural work, including cutting into floors or walls.

Do I Need Planning Permission?

In most cases, installing or refurbishing a shower room is considered permitted development and does not require planning permission. However, if your property is listed or in a conservation area, you should check with your local planning authority before proceeding.

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Understanding Wetroom Waterproofing: The Basics

A shower room or wetroom must be waterproofed — or "tanked" — to prevent water from penetrating the floor and wall structure. There are two primary approaches:

1. Sheet Membrane Systems (the preferred method)

Sheet membranes, such as the Impey WaterGuard, are flexible, pre-formed membranes bonded to the substrate using adhesive and primer. They are the most reliable and widely specified method for professional wetroom installations. Key advantages include:

• Consistent, measurable thickness (typically 1mm)
• Fully bonded to the substrate — no voids or air pockets
• Compatible with underfloor heating systems
• Eligible for manufacturer lifetime guarantees when correctly installed
• Tested to recognised British and European Standards

2. Liquid-Applied Membranes (Tanking Slurry)

Liquid-applied systems are brush or roller-applied coatings that cure to form a waterproof layer. They are commonly used on walls and are suitable for smaller areas. They are generally less robust than sheet membranes for floor applications and may not qualify for the same level of manufacturer guarantee.

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Where Must You Waterproof?

The extent of waterproofing required depends on the type of installation. As a general rule:

• Red Zone (Mandatory): The entire shower floor must be fully tanked. This is the minimum requirement to prevent water ingress into the floor structure and to qualify for most manufacturer guarantees.
• Red & Blue Zone (Recommended): The floor plus all walls within the wet area, extending at least 600mm beyond the shower zone, should be tanked. This protects against splash and condensation ingress into wall structures.
• Full Wetroom Coverage (Best Practice): Tanking the entire floor and all walls of the room provides the highest level of protection, adds thermal and acoustic insulation, and creates a truly seamless wetroom.

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Step-by-Step: How to Waterproof a Shower Room

Step 1 – Prepare the Substrate

The substrate must be clean, dry, sound, and free from dust, grease, and loose material. For timber floors, ensure all boards are securely fixed and there is no flex or movement. For concrete floors, repair any cracks or voids before proceeding. Apply a suitable primer (such as BAL Primer) to improve adhesion of the membrane.

Step 2 – Install the Floor Former

If installing a wetroom floor former such as the Impey Aquadec EasyFit, this should be installed before the membrane. The former creates the fall to the drain and sits flush with the surrounding floor level. Ensure the drain outlet is correctly positioned to avoid floor joists — the Aquadec EasyFit’s patented 360° rotating drain plate makes this straightforward.

Step 3 – Apply the Membrane to the Floor

Cut the membrane to size, allowing it to turn up the walls by at least 100mm at all edges. Apply adhesive or primer to the substrate, then lay the membrane and press firmly to ensure full contact. Use jointing tape at all seams, overlapping by a minimum of 50mm. The Impey WaterGuard system uses a peel-and-stick application, making it one of the fastest and most reliable membranes to install.

Step 4 – Seal All Corners and Junctions

All internal and external corners, pipe penetrations, and wall-floor junctions are the most vulnerable points in any waterproofing system. Use pre-formed corner pieces and butyl joint sealant at all these locations. Do not rely on jointing tape alone at corners — the additional corner pieces provide a robust, three-dimensional seal.

Step 5 – Apply the Membrane to the Walls

Where wall waterproofing is required, apply the membrane to the walls in the same manner as the floor, ensuring a continuous overlap with the floor membrane of at least 100mm. Tape all seams and seal all corners.

Step 6 – Allow to Cure

Allow the membrane and all adhesives to cure fully before proceeding with tiling or other finishes. Refer to the manufacturer’s instructions for specific cure times — typically 24 hours at 20°C, longer in cold or damp conditions.

Step 7 – Inspect Before Finishing

Before applying any wall or floor finish, carry out a visual inspection of the entire membrane. Check for any areas where the membrane has lifted, any unsealed seams, and any corners or penetrations that may not be fully sealed. Rectify any issues before proceeding.

Step 8 – Apply Your Wall & Floor Finish

Once the membrane has fully cured and passed inspection, you can apply your chosen finish. There are two main options for walls:

Option A: Tiles & Grout (Traditional)

The most common choice for wetroom walls and floors. Use a flexible tile adhesive and grout specifically rated for wet areas. Ensure all grout joints are fully filled and sealed. Apply a silicone sealant — rather than grout — at all movement joints (wall-floor junctions and internal corners) to accommodate structural movement without cracking.

Option B: Wetwall Panels (Grout-Free Alternative)

Wall panels — such as those from the Nuance / Wetwall range — are an increasingly popular alternative to tiles, particularly for homeowners seeking a low-maintenance, grout-free finish. Key benefits include:

• No grout lines — eliminates the risk of grout cracking, discolouration, or mould growth over time
• Faster installation — large-format panels cover walls quickly with minimal cutting
• Seamless, contemporary look — available in a wide range of stone, marble, and wood-effect finishes
• Fully waterproof surface — the panels themselves are 100% waterproof; no additional wall tanking is required above the membrane
• Easy to clean — smooth surfaces wipe down in seconds with no grout to scrub

Wetwall panels are bonded directly to the tanked substrate using a compatible panel adhesive and finished with colour-matched trims and silicone at all joints and edges. Always follow the manufacturer’s installation guidelines to ensure the warranty remains valid.

Which should you choose? Tiles offer greater design flexibility and are the traditional specification for commercial and care environments. Wetwall panels are ideal for residential renovations where speed, low maintenance, and a premium finish are priorities.

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Common Mistakes to Avoid

• Not priming the substrate — primer is essential for membrane adhesion; skipping it is the most common cause of membrane failure
• Insufficient overlap at seams — always overlap by a minimum of 50mm and tape all seams
• Unsealed corners — corners must be reinforced with pre-formed corner pieces, not just tape
• Tiling or panelling too soon — always allow full cure time before applying any finish
• Using rigid grout at movement joints — always use silicone at wall-floor junctions and internal corners
• Ignoring pipe penetrations — all pipe and cable penetrations through the membrane must be sealed with butyl sealant

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Choosing the Right Waterproofing Kit

For most residential and commercial wetroom installations, a sheet membrane system is the recommended choice. The Impey WaterGuard Kit is available in five sizes to suit floor-only, wall-only, and combined floor and wall installations from 5m² up to 20m². Each kit includes the membrane, BAL primer, jointing tape, corner pieces, and butyl sealant — everything needed for a compliant, guaranteed installation.

If you need additional accessories such as extra jointing tape, corner pieces, or sealant, these are available separately via our WaterGuard Accessories page at a reduced price when ordered alongside a kit.

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Summary

Waterproofing a shower room correctly is non-negotiable — it protects your home, your investment, and the people who use it. By following the guidance in this article, adhering to the relevant UK building regulations and British Standards, and using a quality membrane system with the correct accessories, you can be confident of a watertight result that will last for decades.

If you have any questions about specifying the right waterproofing system for your project, our team is here to help. Get in touch and we’ll be happy to advise.

Tags

Building Regulations DIY Impey Installer Guide Tanking WaterGuard Waterproofing Wetroom

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