What are the 5 key technical aspects to designing a wetroom?

A wet room is the ultimate showering space but what do you need to consider when designing wetrooms that deliver a beautifully functional solution, whatever the project requirements?

1. Drainage

The removal of the waste water is the major consideration in the design of a wetroom.

It is critical to specify the drainage solution that is required for the wetroom at the planning stage as this is directly related to the type of floor build up needed, ie timber or solid, the flow rate required and the number of traps required to support this flow rate, the type of grill required ie square or linear, the positioning of the grill in the wetroom, ie wall-abutted or centred in the shower area, and the type of tiles to be used, ie size, finish, design.

2. Floor build-up

The Federation of Master Builders states: A successful wetroom not only needs to be tanked perfectly and made watertight, but it also needs an absolutely solid sub-base due to the fact that one of the biggest problem areas can be leakage where movement occurs (especially in older homes).

Wetrooms can be installed on both timber and solid floors but they need to be prepared in different ways and mindful of building regulations if they necessitate any structural modifications.

– Timber floors normally require the installation of a floor former before drainage and waterproofing systems are fitted. This former will have the necessary gradient. Floorboards need removing to facilitate the installation of the floor former. It is essential to choose floor formers that have been certified to withstand significant loading weights.

– Solid floors can vary depending on whether in a new build or an older property. In a new property the drainage system and connection to the mains needs to be done prior to the screed being laid. A gentle and consistent slope in the screed is necessary – typically 1:40 and 1:60 run-off depending on the shower. In an older property the old screed needs to be removed before a drainage system can be installed and new screed laid on top.

* If underfloor heating is part of the design, then this needs to be installed at this stage. Energy saving and energy efficiency are to be considered at this stage as well as the most appropriate choice of the heating system.

Pre-formed trays can be used on multi-storey projects. These have a built-in gradient (or even gradients) and a waste and are installed between the joists or screed level with the rest of the floor. The load bearing weight of the joists must be tested to ensure they can support the weight of a wetroom and the floor void can accommodate the drainage system.

3. Waterproofing

Waterproofing, or “tanking”, is a crucial part of the installation process and typically a waterproof membrane is used to line the whole shower floor area prior to the application of the tiles. It must extend at least 1m beyond the intended “wet area” but can be used throughout the entire bathroom floor. It is generally used in conjunction with a wall membrane that fits around the walls to prevent water penetration.

Additional waterproofing using tape to walls prior to tiling, and to any joins in the membrane is recommended.

4. Tiling

Tiles are the usual choice for both the walls and the floor in a wetroom but whether stone or ceramic they need to have a water resistant surface and meet the requirements of BS EN 14411 Ceramic tiles – Definitions, classifications, characteristics and marking”.

The choice of material can be influenced by considerations relating to weight, to budget, to maintenance. The flooring must be non-slip: safety is paramount in wetroom environments. In hospitals and care homes the flooring type will need to meet the pertinent regulations.

The following standards provide further guidance on tiling and flooring:

BS5385-4 Wall and floor tiling – design and installation of ceramic and mosaic tiling in special conditions. Code of practice

BS EN 12004 Adhesives for tiles and BS EN 1388 Grout for tiles. Requirements, evaluation of conformity, classification and designation

For the Health & Care sector the following standard applies:

BS 8300 Design of Buildings and their approaches to meet the needs of disabled people.Code of practice.

5. Ventilation

High humidity and condensation can affect materials and walls in the wetroom area so it is essential to consider appropriate ventilation especially in a windowless environment. The provision for vents, especially in basement areas, and/or windows, perhaps Velux type windows if the wetroom is in a loft conversion, needs to be part of the architectural specification.

In summary, correct design and specification will result in a safe, convenient showering solution in a fully waterproofed space for total peace-of-mind.

If you’d like to learn more about the technical considerations when building a wetroom please contact our technical team on 01460 258 682 or contact us to request one of our RIBA approved CPDs.

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