3' x 4' Bathroom Example

The Tiniest Half-Bathroom Possible

I live in a small space with my husband and two kids. We love where we live and aren’t ready to move, so we’re making it work. The most difficult thing about our small space is that we only have one bathroom.

Because we live in a condo/townhouse, we could add a bathroom, but we can’t add on to the house. So, I’ve been considering adding a tiny half-bath somewhere in our already tiny house. Which leads me to the question: What is the tiniest possible half-bath?

Not as small as I hoped, it turns out. According to my research, a toilet requires a 30″-wide spot to sit in to adhere to U.S. building codes (that’s 15″ from the center point on either side). So, the tiny bathroom needs to be at least 30″ wide. Possibly wider when considering sink placement (we’ll get to sinks later).

Basic Code Requirements For Bathrooms
Image source: Fix.com Blog

The length of the bathroom is the next factor. Toilets (and sinks) require 21″ in front of them by code. So, the length the toilet projects from the wall plus 21″ is the minimum possible length of the room. The smallest standard toilets I could find project about 2425” from the wall (24″ toilet available here, 25″ toilet available here).

Valentina Close Coupled Toilet from Drench projects about 24"
Images, from left: the Better Bathrooms Close Coupled Compact Space Saving 600 Pan and Cistern projects about 24″, the GALBA small toilet projects about 25″, the Valentina Close Coupled Toilet projects about 24″

I also found some small toilets with the tank in the wall that project only about 20” and 22” (22″ toilet available here) and a high tank toilet that projects only about 20” (20″ toilet available here). With these options, I think we should allow 20″ or 25″ for the toilet plus 21″ in front of the toilet, equaling a minimum bathroom length of 41″ or 46″, depending on toilet choice.

Images: Basong White Wall-Hung Dual-Flush Toilet Bowl In-Wall Tank System projects about 22″, Barclay 2-413WC Victoria Vitreous China Round Front Adjustable High Tank Toilet projects about 20″

What about the sink? By code, a sink requires a space 20″ wide to sit in and 21″ in front of it. There are small sinks that only project from the wall about 12” (12″ sink available here), or a corner sinks that are 12.8″ x 12.8″ (corner sink available here). The sink can be placed next to, perpendicular to, or across from the toilet — there are many ways to arrange the two to maximize space.

Images: Fine Fixtures Small Wall Mount Sink projects about 12″, Cheviot Products Inc. 1349-WH-1 Corner Wall Mount/Vessel Sink projects about 12.5″

One idea I had was to place the sink and toilet perpendicular from each other so that the 21″ space in front of the toilet and the 21″ space in front of the sink overlap. Here’s a quick example I made in a floorplan app of a 3′ x 4′ (36″ x 48″) bathroom with a toilet that projects 25.5″ (22.5″ clearance) from the wall and a 12″ x 12″ sink.

3' x 4' Bathroom Example

I think the above example meets building code (although I’d check with a contractor before building it) and maximizes the space. The toilet is set slightly to one side to prevent the sink from blocking the 21″ required in front of the toilet. Obviously, a few inches can be cut depending on whether you choose a smaller toilet or sink. (Edit to add that the above picture doesn’t take into account the 20″ clearance width for the sink. This design may work better with a sink that projects 6″ from the wall.) Another thing to remember is that walls take up space, too — about 4.5-6.5″.

Another option to save space is installing a corner toilet. It’s hard to find a straight answer on this, but it appears that as long as there is the 21″ space in front of the toilet, the 30″ width doesn’t really come into play (disclaimer: again, I am not an expert here). I found a small corner toilet that projects only 26.5” from the corner and a more standard one projecting about 30“. If you add a 27″ or 30″ projection to the 21″ space in front of the toilet, a square bathroom with a diagonal of 48″ or 51″ could work, in other words, a 34″ x 34″ or 36″ x 36” room for just the toilet.

RAK Evolution Corner Toilet projects only 26.5"
Image: RAK Evolution Corner Toilet projects only 26.5″

To add a sink to this scenario, I would place the corner toilet in one corner and a sink in a corner of the same wall, so that the 21″ allowance in front of both features can overlap. You’d need to add a few inches to length of the room along the wall with the sink to give the sink the required 20″ width allowance (10″ from the center point in each direction).

Here’s a quick example floorplan for this scenario, where the room is 37″ x 34″ (the wall with the door is longer). The toilet is a corner toilet projecting 26.5″ with 21.5″ clearance in front of it. The sink is a 12″ x 12″ sink placed four inches from the wall to the left (to give it a 20″ width allowance) and has 22″ clearance in front of it. I think this example would meet building codes (but barely!).

34" x 37" bathroom

Or I could get rid of the sink all together and install a sink on the toilet or a toilet with a built-in sink. It might sound odd, but these sink-on-toilets are designed so that the built-in sink uses only fresh water, and the used sink water fills the toilet tank, recycling the water as flush water. So, it’s water-saving, space-saving, and a great conversation piece. A sink-on-toilet would require a toilet with a standard tank, though, so the tank-in-wall or high-tank toilets wouldn’t be an option.

Caroma Profile Smart 305 Toilet with built-in sink
Image: Caroma Profile Smart 305 Toilet with built-in sink

Another thing to consider is that code requires the doorway to be at least 32″ wide. So, the room needs to be at least 32″ wide in one dimension. But then you need to add the door frame, which gets you to 34″ for the door.

Final minimum half-bath size? I’m going to say 34″ x 34″ — with the smallest corner sink-on-toilet. With the smallest non-corner sink-on toilet, I think it would be 30″ x 46″.

With all these considerations in mind, I also need to find a space in my house to add a half-bath. I was hoping to put my bathroom in one of my closets. Unfortunately, none of my closets are perfect for the project. I thought the closet under my stairs would be ideal, but the ceiling height is too low. By code, the ceiling must be 80″ high at the front of the toilet and 60″ high at the back. Unfortunately, my ceiling slope is too steep for this option to work.

In tiny homes, some people are using are composting and dry flush toilets instead of traditional toilets. These toilets are portable and not connected to plumbing, and so they don’t need to adhere to building code. Composting toilets have some associated odor, and so I don’t think it’s a good option in a regular house. Dry flush toilets are supposed to be odor-free because they use a new technology that basically vacuum seals your waste (like in The Martian!). That’s intriguing, but I’m not ready to give up on plumbing just yet.

Dryflush toilet by Laveo
Image: Dryflush toilet by Laveo

I haven’t found a space in my house that is ideal for my tiny bathroom yet, so it’s still a dream for now. I wrote this post to share my research, for those of you considering their own tiny bath project. If you do, please get a contractor or architect to sign off on the project — I am not a building professional and this is all just friendly advice.

Are you planning to add a tiny half-bath to your space? What are your thoughts on designing one?

Note: If I got anything wrong here, please send me a friendly note or comment to let me know!

Disclaimer again: I am not a building professional and everything in this article is strictly my opinion. Use this information at your own risk. Do not rely on information found here without independent verification.

Some helpful links:

Information on building codes: http://homeguides.sfgate.com/dimensions-building-regulations-small-bathroom-68909.html

This article has some great images to guide you: https://www.fix.com/blog/best-bathroom-design-rules/

Another good article about small bathrooms: https://www.pickatoilet.com/compact-toilets-for-small-bathrooms/


Add comment