Proper waterproofing in sanitary facilities – protecting against damage and moisture

From planning to execution, ensuring structural waterproofing is able to provide long-term protection against moisture is a significant challenge. A lack of due care and attention here risks costly repairs later on, delays or claims for compensation. For planners and tradespersons alike, this means well-designed approaches, tried-and-tested system solutions and clear coordination are needed to properly fulfil the technical requirements.

Why structural waterproofing is important
Starting point: the DIN 18534 standard
Requirements for sanitary facilities on commercial and public premises
Waterproofing by tilers
System solutions from SCHELL: expansion sleeves

Why is good waterproofing so important?

From structural damage and rework to legal disputes and claims for compensation: when things go wrong in construction, the outcome is often very serious. One of the commonest reasons for such problems is waterproofing that doesn’t meet the technical codes or standards.

Structural dampness: leaving the door open to water

Substandard waterproofing can cause significant structural damage that not only affects the building fabric itself but also leads to health risks for the property’s inhabitants. Areas that are not watertight permit the ingress of moisture – with catastrophic consequences.

Typical problems:

Mould
Wood rot
Material failure
Structural damage

Important: Even small problem areas can develop into serious issues later on.

Poorly executed waterproofing can result in massive repair bills

Water damage is often discovered too late – when the damage becomes visible and is already expensive to fix.

Especially problematic:The longer moisture damage remains undetected, the more extensive and expensive the subsequent repairs will be.

Water pipe damage: overview of costs and causes (figures are approximate)

Source: haustec.de, sanitary/installation equipment
Total insurance claims for water pipe damage	EUR 3.08 billion/year Average claim	EUR 2,717 Substandard waterproofing as a contributory factor	1 in 4 claims

Key standards for structural waterproofing

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Interior waterproofing: a brief guide to the DIN 18534 standard

DIN 18534 Waterproofing for indoor applications:

Part 1: General rules for all types of waterproofing

Part 2: Waterproofing with waterproofing materials in sheet form

Part 3: Waterproofing with liquid-applied waterproofing materials in conjunction with tiles and paving(AIV-F = composite waterproofing – liquid waterproofing materials)

Part 4: Waterproofing with mastic asphalt or asphalt mastic

Part 5: Waterproofing with waterproofing materials in sheet form in conjunction with tiles and paving(AIV-B = composite waterproofing – waterproofing materials in sheet form)

Part 6: Waterproofing with waterproofing materials in panel-shaped form in conjunction with tiles and paving(AIV-P = composite waterproofing – panel-shaped waterproofing materials)

Important: Parts 2 to 6 must always be considered together with Part 1.

Joint responsibility for plumbers and tilers – requirements apply to both trades

The waterproofing of wet rooms – particularly showers – and their associated requirements is typically assumed to be a task for the tiling trade. Yet it’s not quite that simple. Indeed, DIN 18534 clearly states the following: ensuring the professional waterproofing of interiors is the joint responsibility of all of the trades involved.

Accordingly, while tilers have a part to play, they share responsibility with planners, installers and other trades for ensuring that the work meets the required standards.

Good practice: Start by getting everyone on the same page. Getting the work by the various trades properly coordinated early on saves time and money, and avoids unnecessary rework.

Requirements for sanitary facilities on commercial and public premises

High-traffic areas – greater wear and tear

Higher rates of use and larger volumes of water make the requirements for waterproofing much more extensive in sanitary facilities on commercial and public premises.

Especially problematic:

Communal showers (column/row) and changing rooms
Swimming baths
Extensive, floor-level shower areas
Areas regularly/continuously exposed to water spray, service water and water accumulation

Other, additional risks may include blockages, flooding and vandalism

Why water exposure classes make all the difference

The water exposure classes defined in part 1 of DIN 18534 are authoritative here, as the DIN standard categorises wet rooms into four water exposure classes based on the intensity of this exposure. This classification then forms the basis for waterproofing planning. The higher the class number, the more demanding the requirements for processing, material, installation conditions, etc.

The water exposure classes are as follows: W0-I (low water exposure), W1-I (moderate water exposure), W2-I (high water exposure) and W3-I (very high water exposure). As a general rule, domestic bathrooms are assigned a water exposure class no higher than W2-I, and class W3-I is therefore basically reserved for use with public or commercial premises. The following diagram clearly illustrates how the planning decisions taken affect the respective interior’s water exposure class.

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Good practice: The water exposure class must already be taken into account as part of draft/preliminary planning. This allows local conditions to be checked early on – such as feasibility, quality of the existing structure for renovations and any potential extra work needed to ensure that the requirements for the substrate are met.

Why crack classes and room usage classes are also important

Alongside water exposure classes, DIN 18534 also defines crack and room usage classes to aid in the selection of waterproofing options.

Crack classes: Crack classes specify the extent to which the waterproofing needs to accommodate movement and later crack widening in the waterproofing substrate over the long term. R1-I is the typical crack class assigned to interiors.

Room usage classes: As the name suggests, room usage classes relate to how the room is used, and offer information about the additional waterproofing measures that may be required to improve the interior’s ambient conditions and avoid the formation of mould.

Key definitions from the standard:

W0-I (low) Surfaces with infrequent exposure to water spray	R1-I (up to approx. 0.2 mm)	Wall surfaces in domestic kitchens and in bathrooms outside shower areas Floor surfaces in domestic areas without drains – e.g. in kitchens, utility rooms, guest WCs W1-I (moderate) Surfaces with more frequent exposure to water spray or infrequent exposure to service water, without heavier exposure due to accumulated water	R1-I (up to approx. 0.2 mm)	Wall surfaces above baths and in showers in bathrooms Floor surfaces in domestic areas with drains Floor surfaces in bathrooms without/with drains and without significant exposure from shower areas W2-I (high) Surfaces with more frequent exposure to water spray and/or service water, with occasional heavier exposure on floor surfaces due to accumulated water	R1-I (up to approx. 0.2 mm)	Shower wall surfaces in sporting venues/commercial premises Floor surfaces with drains and/or gullies Floor surfaces in rooms with floor-level showers Wall and floor surfaces in sporting venues/commercial premises W3-I (very high) Surfaces with very frequent or prolonged exposure to water spray and/or service water and/or water from extensive cleaning activities, with exposure intensified by accumulated water	R1-I (up to approx. 0.2 mm)	Surfaces near to pool surrounds in swimming baths Showers/shower facilities in sporting venues/commercial premises Surfaces in commercial premises (commercial kitchens, laundry services, breweries, etc.)

Waterproofing by tilers

Why the use of a SINGLE system is always recommended

DIN 18534 states that the sealing tapes, sleeves and accessory parts to be used must have been tested and approved together with the waterproofing materials from the respective manufacturer.

Once a waterproofing system has been selected, it must then be used exclusively within the project.

‘Latent defects’ due to untested combinations

The use of multiple waterproofing systems – such as the rest of the sealing tape from manufacturer A combined with a waterproof coating from manufacturer B – risks legal claims for latent defects.

Sole exception: The property developer signs this off and formally approves it as a custom combination – although this is not a recommended approach.

System solution for waterproofing: the certified expansion sleeve from SCHELL

What makes the expansion sleeve a system solution?

Expansion sleeve for structural sealing of SCHELL masterboxes according to DIN 18534:

concealed fittings from SCHELL are installed with the SCHELL masterbox – which needs waterproofing compliant to the DIN 18534 standard.

Important: This requires a solution approved for use with the SCHELL masterbox that has been tested by the manufacturer.

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SCHELL offers a matching and certified expansion sleeve, with installation and the installation instructions both being part of the certification process, and therefore properly tested, alongside compatibility with popular waterproofing systems.

Overview of technical specifications

Waterproofing to DIN 18534
Fulfils all requirements for water exposure classes W0-I to W3-I
KIWA certification – product plus installation
Approved for use with:
- Otto Coll M 500 (hybrid adhesive/sealant)
- ARDEX S7 Plus (flexible waterproof coating)
Additional adhesion to masterbox with sealing/adhesive tape
Colour coding (to avoid mix-ups with old and new products) plus SCHELL logo for no-hassle installation
Clear-cut markings avoid potential installation errors

Installation: The expansion sleeve is fitted over the masterbox and pressed down against the existing substrate.