In this post, we will take you through the installation practices that are needed for bathrooms that contain wet rooms, showers, or bathtubs. Bathrooms are split into ‘zones’ and you will need to focus on specifications for every zone to ensure that you adhere to the rules and regulations in place. 

What are the zones and environments?

You need to understand the zonal considerations for every environment, i.e. wet room, shower, or bath. Electricians and candidates need to flag any details that are ambiguous because specialist locations can be volatile. All installations need to be carried out with assurance and confidence. 

For shower wells and bath tubs, there are three associated zones. However, there are only two accredited to wet rooms. There are numerous parts to think about for every zone based on how likely the area is to be exposed to wetness. 

Understanding the Bathroom Zones 18th Edition

You should refer to Section 7 of the BS 7671 18th Edition. This part provides details about the appropriate regulations, as well as giving advisory notes regarding different specialist locations, for example, bathrooms. 

The box is one element that is consistent throughout the entire implementation. This is a reference to a parameter (an imagined one) that follows a standard guideline of measurements, irrespective of the context, and the height of this always needs to be 2.25 m, or the highest fixed outlet or head, i.e. whatever is higher. 

The bathtub, shower basin, or wet room will dictate the width. To give you some reference, the majority of contemporary bathrooms measure approximately between two and a half and three metres, meaning there should be ample room between the ceiling and the upper box level. 

Moreover, any 230V transformations deployed need to be 30mA protected, and guidelines need to be followed on whether or not these units can be facilitated outside or inside bathroom spaces, depending on the size of the room.

Installation of bathtubs as per Bathroom Zones 18th Edition

For bathtubs, your ‘box’ size needs to correspond to the criteria below:

  • Weight – This needs to be the bathtub’s weight, and then you need to add on 60 cm. Therefore, if you have a bathtub that measures 70 cm, you should have a box width of 130 cm. 
  • Height – As a standard, electricians need to mark this at 2.25 m. or, if the fixed head outlet is higher than this, mark down the height of that. 

The surrounding perimeter of the dimensions mentioned relates to the area of your box. Bathrooms have three fixed zones:

  • Zone 2 – Zone 2 refers to the area that is immediately adjacent to your bathtub, i.e. this is where we added the extra 60 cm for safety reasons. You will need to make sure that any equipment you use is subject to IPX4 grading. Nevertheless, if you are going to be installing shaver sockets, this must be done to the BSEN 61558-2 standard. You need to search for a position whereby possible water spray is not likely. Self-sockets and switches are allowed in this area. A ceiling pull switch for any associated shower facility needs to be mounted above the 2.25 m threshold. 
  • Zone 1 – Next, we have Zone 1, which is the area from the floor up to the box’s upper limit, i.e. the standing area above the bathtub. With regard to width, the zone incorporates the bath’s full expanse – i.e. not only the seating area. As a consequence, candidates need to think about external bathtub handles when they calculate this space. If the area under the tub is easy to access, it should be integrated into this zone. Nevertheless, if it is blocked by a panel or barrier, this would be deemed an outside zone. This needs to be accordingly prepared to the provisions set out under this space, which is why it is imperative to get to grips with the next rules and regulations that are in place. In terms of lighting, it must be coordinated on either PELV or SELV circuits, and it should be limited to 60VDC or 25VAC. If an electric shower is needed, compliance with the IPX4 rating is a necessity. 
  • Zone O – Last but not least, we have Zone O, which is the most dangerous region for installation. Because of this, there is a number of extra precautions that need to be taken. Zone O is a reference to the area you would sit while you are in the bath. When you install this part of the zone, you need to ensure that any electrical equipment you use is IPX& rated, which will dually accommodate submersion. It is vital that the voltage does not go above 30VDC or 12VAC in this region. Moreover, it needs to be an extra-low voltage circuit that is separated only, and you need to locate a 230V transform that supports this end outside of the bathroom. Extra-low voltage cables, which are also referred to as ELV cables, are permitted for travelling in this zone and others.

For the rest of the room, this is known as the outside zone. This is inclusive of the area above the box. 

This just gives you a brief overview of the regulations for wiring when installing a bathtub. You then need to learn about wet rooms and showers as well. This is why taking a certified and reputable course is so important. 

Here at Skills Training Group, we are delighted to offer the 18th edition course, and we will make sure you acquire all of the knowledge you need within just three days so that you can ensure all installations are in accordance with the law.

What about showers?

Showers adhere to the same guidelines as bath tub installations. Nevertheless, it is vital to note that the shape of the unit does create some nuances. 

When we are discussing showers, the foot basin space is referred to as Zone 0. Zone 1 is considered the immediate area above this, up to 2.25 m in length. This mimics the measurements of the foot basin in terms of width. Again, Zone 2 is 0.6 m, yet this time it is registered from the foot basin’s outside edge. You are also going to follow the same guideline patterns as a bathtub for the Outside Zones. 

Zones for wet rooms 

Finally, we have wet rooms, which differ quite considerably when compared with bathtubs and showers. As a ‘wet room’ is a free-standing space that does not have any unit attached to it, we refer to the projected line as Zone 0, rather than being linked to any sort of physical entity. This measurement starts from the ground level and is then 10 cm from this. Zone 1 is considered the length up to the 2.25 m upper level. 

Each will share the same width, which is defined as a circle with a radius of 1.2m, with the point in the centre relating to its plughole or fixed water outlet. These dimensions create the overall safety box, which we explained earlier in the guide. In situations whereby the circle’s flow is disturbed due to partitions, it will wrap itself around, ensuring it is still aligned with the measurements we mentioned above.

In a wet room capacity, you do not have any Zone 2. Therefore, any candidate should assume that the space external to Zones 0 and 1 is deemed the Outside Zone. 

If you are going to install underfloor heating in the bathroom in question, this is something that also needs to be considered very carefully. You need to make sure that any cables that pass via Zones 1 and 2 are RCD, 30mA protected.