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A Design Guide to Bathrooms

Updated: Feb 26

In this post I want to show you how to create a great bathroom in your home. I'm going to use images from several of my own designs, including this project, as an example. I have been a self-employed Architect in the UK since 2009. In my day job, I specialise in designing private homes. Now, since I’m an Architect and not an interior designer, this guide is based on the assumption you aren’t just updating an existing bathroom. I'm assuming you want to create a brand new bathroom where there wasn’t one before. Either altering or extending your existing home or building a new house from scratch.

We aren’t just talking about colour schemes here, we are going right back to basics. I

I will discuss how many bathrooms a home needs,

where to place the main bathroom in your home,

how drainage in an existing property can limit your options,

the minimum size for a shower room,

how to layout a luxury bathroom,

ventilation requirements

and how to properly heat your bathroom.

Feel free to skip ahead if one of these topics is relevant to your project.

This post is part of a series, where I make a design guide for all the major rooms in a home. I've previously made a video about kitchen and bedroom design and I'm currently working on design guides for bedrooms.

Much of the information in this design guide will apply anywhere but I should also say that since that I am going to reference building regulations in the UK. If you are watching from outside the UK be sure to take advice from an experienced local Architect on which regulations apply to your bathroom.

When it comes to the main rooms in a house, most people have one kitchen and, ideally a separate bedroom for every person plus one spare for a guest. But how many bathrooms should a property have?

There is no easy answer to this. If money were no object, every bedroom would have its own ensuite and there would be main bathrooms on every level of the house. Our building regulations require at least one sanitary accommodation on the principal living level. If your home is on more than one floor, that’s usually the floor with the kitchen.

This means, to meet the minimum standards our building regulations you only need one bathroom per home. I am going to assume you will have as many bathrooms as you see fit. This design guide will focus on how to make one, really great bathroom. So let's look at location, where is the ideal place for a bathroom in your home?

If you are building a new house, I think a bathroom should be off the main circulation space. Whether that’s the hallway or stairs if you have one. The bathroom should be near the main living space but not directly next to it. It's always a good idea to have two doors between the bathroom and any hallway.

When I was a student, I shared a flat with four other guys and we had a bathroom just off the living room. It was so accessible, you open the bathroom door and watch the TV while sitting on the toilet. Needless to say, this innovation is not something I've been able to persuade my clients to adopt. There is such as thing as being too close for comfort.

If you are planning to alter an existing building, your options might be limited, especially if your property is a flat or apartment with neighbours downstairs.

I designed this bathroom

This bathroom was in a flat but the property was over two stores and we were able to run the pipes in the floor without any major issues because the floor below was part of the same property. If there was a separate property downstairs this would never have been possible. You see, no matter what your floor is made from, there is a point halfway between your floor and your neighbours ceiling, where your ownership stops and their ownership begins. Nothing of yours can cross that invisible line, including pipes.

The pipe run within the floor. Not possible if you have downstairs neighbours.

This can be a show stopper if you want to have a shower tray that is flush with the floor. Showers must have a trap, or bend in the pipe where the water flows away. This takes up quite a lot of space and isn't always possible if the property is a flat or apartment. People who aren’t familiar with drainage pipes are often surprised by their size. A toilet needs a pipe 100mm across. Most sinks, baths, and showers need a 50mm diameter pipe.

Not only that but these pipes cannot be laid flat, otherwise the liquid inside wouldn’t go anywhere. Bathroom drainage pipes are usually laid to a fall of 1 in 60. So for every 60 meters or feet they run horizontally, the pipe must drop one meter or foot vertically. What this means is that the further your bathroom is located from the existing drains, the deeper your pipe has to drop in order to get wastewater to those drains. My advice is to have a professional check this one out before you finalise the location of your big new bathroom.

But, on that point, how big should your bathroom be? Well the regulations don't set an upper limit on the size of bathrooms but they do have minimum sizes.

Excerpt from the Scottish building regulations showing activity spaces in bathrooms

The regs ask designers to show activity spaces in front of the toilet, wash basin, shower or bath. As well as a space 80cm wide by 110cm long inside the door. These activity spaces can overlap and in my experience, the minimum size for a functional shower room breaks down into two options.

A long rectangular room, with a door in the middle. The toilet at one end, the shower at the other end and a small wash basin opposite the door. This would measure about 3m long and 1.1m deep. The other option is a square room roughly 2m x 2m.

Now you have some understanding of how the building's regulations operate, let's kick it up a notch and talk about luxury.

3D sectional perspective of the bathroom I designed

This project from 2012 combined a free-standing bath with a feature shower, recessed shelves, wall hung toilet with a concealed cistern, and a bespoke wall-mounted vanity unit. Other bathrooms I’ve designed use many of these same features.

The first thing to get right when designing a luxury bathroom is the sense of arrival. This space must say wow when a person walks in. And to achieve this there should be a focal point.

I also designed this bathroom

In this bathroom, it's the free-standing bath and these aren’t as easy to achieve as you might think. For one thing, they are heavy, even when empty, but keep in mind these things can hold hundreds of liters of water. It's possible a large feature bath could hold half a ton of liquid. So if you want to put one on the upper floor of your home, that floor will need reinforcing to carry the weight.

Free-standing bath, with a free-standing mixer in the background

Free-standing baths often have free-standing mixers. These are mounted to the floor and can be a problem if someone slips getting out of the bath, and grabs the mixer for support. If it's not secured to something robust, it will break and the water pipes inside could rupture. I've seen bathroom companies sell these products to my clients without mentioning any of these issues.

I love wall-mounted toilets, not just because they look cool but because they are also practical. It's much easier to mop a floor around a toilet that is wall-mounted. But to achieve this, the toilet needs a concealed cistern, like this.

concealed cistern for a wall mounted toilet

These are designed to fit inside a timber frame wall so keep that in mind if you are thinking about retrofitting one into a room with solid masonry walls. This room was lined with a new stud frame on all sides. Not only did that allow us space to hide all the pipes and wires, but it gave us the opportunity to create recessed shelves, like this, in the shower.

Now, these elements also have to work with your tiles, it doesn’t happen by accident. To help design the space and communicate the eventual layout of the tiles and units to the contractor, we use internal elevation drawings.

internal elevation drawing of the bathroom wall, showing how the tiles and units align

These are literally drawings of each of the four walls, showing the exact location of everything. Top tip, your wall tiles will almost certainly not fit exactly into your bathroom. To avoid weird cuts at one corner, the best way to set out the tiles is from the center of the room. Start in the middle and work out from there. If there has to be a cut, there will be two equal-sized cuts at each corner.

Also, if you have large-format ceramic tiles keep in mind these are baked in an oven and will have imperfections. They often bow in the middle and this means that if you stack them in a running bond, like this. The thicker part of the tile above will cast a shadow over the thinner part of the tile below.

Wall tiles in a running bond pattern

These tiles are often sold in packs advertised as being rectified, that is the manufacturer sorted them out so the most bowed ones are removed. Despite that, I've seen this go wrong and it’s best to stack bond big ceramic tiles, one directly above the other. Like this.

my joinery drawings for the bespoke vanity unit

I did all the bespoke joinery drawings for this vanity unit. This took a huge amount of time and I am very proud of the end result but afterwards, I decided never to do it again. I lost a lot of money on this project and clients can usually buy these items off the shelf. This project was from the early days of my practice and I chalked it up to experience.

It might come as a surprise that our building regulations do not require a bathroom to have a window. This bathroom has a huge window with really great natural light and if you can create a bathroom with a window it's a big win, for ventilation as well as illumination. While the regulations do not require a bathroom to have a window, they do require the room to have a mechanical extract fan which removes steam and moisture from the building. I can't begin to say how important this is. If moisture builds up within your home it leads to mold, fungus, and rotting timbers, not to mention respiratory problems for the occupants. It's not good. So even if your bathroom has a window, it will also need an extract fan. But if your bathroom doesn’t have a window, then the door to the room must have a trickle vent. This replaces the air which has been sucked out by the extract fan. Without this, the fan won't work properly, and moisture will build up in the room.

My final tip for a great bathroom is to use electric underfloor heating. Regular, wet underfloor heating is great but it runs very hot and can take a while to heat up. Electric systems are almost instant and don't get as hot as wet systems. This is ideal under the floor tiles of a bathroom, just flick a switch and within seconds the floor is warm but not so hot, it might scald your bare feet.

bespoke vanity unit with heated mirror above

We used an electric heating mat behind this mirror to keep it warm and prevent condensation from fogging up. You can buy mirrors with a heating element built in but this mirror was bespoke, made to measure exactly between the wall tiles. If you are planning something similar talk to an electrician so that it gets done safely.

You also need to think about the towel warmer. These are often hybrid systems, a wet radiators run from your central heating but with an electric element included inside, so they can warm up independently on their own.

On the central heating system, if you have several bathrooms in your property it's a good idea to have a hot water cylinder in the house. This will store hundreds of liters of hot water so that everyone can have a shower or bath at the same time without having to wait for the boiler to heat the water first.

If you are going to do luxury you need to think about the practical stuff first.

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