What is the smallest you can build a bathroom?
The smallest you can build a full bathroom with a toilet and shower is 18 square feet. The bathroom is able to achieve these small sizes by using smaller toilets, walk through showers and no sink or smaller sinks. To build a small bathroom you must very efficient with space in the design.
Why build a small bathroom?
You want to build a small bathroom when there is a lack of available space to build. Houses only have a certain amount of square footage that can be used and sometimes you must be efficient with bathroom design to make the most of that small space. I don’t value a large bathroom space so it makes sense for me to design the bathroom to my specifications. The idea is to get maximal functionality for the least square footage.
Where to build a small bathroom?
Small bathrooms are built in smaller structures or unusual areas. Small structures like tiny homes, RVs, boats, container homes, and old houses all need to use space efficiently. They are also a good choice for a basement bathroom, garage bathroom, outside bathroom, or studio apartment bathroom. The biggest requirement for a small bathroom is that they are built close to plumbing.
How to build a small bathroom on a budget?
I built my bathroom with free reclaimed building materials. What I couldn’t get reclaimed I bought used from habitat for humanity. The bathroom was designed small and uses affordable materials so it meets any budget.
How much does it cost to build a tiny bathroom?
| Material | Mosaic tile shower | Toilet | Shower valve, shower head and pex | Shower pan liner, drain, cement | Door | Shower curtain and rod | Total |
| How much | Free tile!, tile adhesive, grout | 1 | 3 pex pipes, 1 shower valve and head | 3 bags cement, 1 liner, 1 drain | 1 bifold door | Copper pipe, curtain, pipe fitting | |
| Cost | $30 | $52 | $107 | $30 | $20 | $23 | $262 |
How do I design and build a small bathroom?
I have built and designed two small bathrooms. My bathroom in the tiny house is a 6’x3’ space which is 18 SqFt total. My bathroom in the garage I built is 5×5 or 25 square feet pictured above. In the tiny house bathroom to use space efficiently I designed a walk through shower with the toilet facing out from the back wall. The shower floor was going to be a mosaic from old tiles left over from other projects.
What doors did I use?
Using space saving doors is very important to build a small bathroom. The door to the tiny house bathroom would be able to fold into the stud bay of the wall to make space when the shower is not being used. I used a pocket door in the garage bathroom to save space. In my garage bathroom I used a smaller 18” long toilet and small bathroom sink to save space.
The sink was a 1.5 by 1.5 pedestal that I bought from home depot pre made. Instead of using a mosaic shower I bought the smallest 3’x3’ shower pan they had. In the tiny house the bathroom has no sink to save more space. I was able to do this because there was the kitchen sink very close to the tiny house bathroom so it was able to function as the bathroom sink as well.
How did I do the shower curtain holder?
For both bathrooms I built my shower curtain rod to be made of copper pipes that are attached to the walls with flanges. In the tiny house the shower curtain that has southwest theme with colors that match the house. The curtain I wanted to use wasn’t long enough so I used dog tag chains to extend the curtain until it reached the floor. In the garage bathroom I decided that a bright pink shower curtain would match the other pink colors in the bathroom.
The walls of the bathrooms were in the same style as the rest of the house. In the tiny house I implemented an open stud bay design with the walls being painted white.
How to get started to build a small bathroom?
You will start by making markings on the subfloor where you want the toilet flange and shower drain to go. If you have already existing plumbing in place than you can build around the existing plumbing. Otherwise you can mark these holes for when the plumber installs the rough in plumbing. I only did the plumbing in the bathroom and hired out for the rough in plumbing under the house.
How do I determine where to place a toilet flange?
In the tiny house I used a full sized toilet so I marked 15” off the wall for the location of the toilet flange. You can choose to use a smaller toilet to save even more space and your toilet hole may be a different distance from the wall. My small 18” long toilet in the garage only needed 10” off the wall to fit. I made sure the toilet flange holes were equidistant to the walls and other items in the bathroom.
How do I determine where to place the shower drain flange?
Next is placing the hole for shower drain pipe. These next few paragraphs will be about the tiny house bathroom because in the garage bathroom I bought a 3×3 pre made shower pan. The toilet in my tiny house took up 2 feet of the 6 foot length of the bathroom. This meant I had 4 feet left to work with. I measured and chose a location at 2 feet from the toilet and 2 feet from the end of the bathroom. Make sure the measurement is equidistant from both walls. This central location would be where a hole would be drilled in the subfloor for the plumbing.
The drain pipe for the shower had to be the lowest location in the bathroom for draining. For this reason I needed to raise the area up under the toilet so there would be a slope from the toilet to the drain pipe. I used 2 sheets of durrock cement board under the toilet flange to raise the flange up. Then I used tile adhesive between the sheets and screwed them down. To finish, cover any cracks between the durock sheets with tile adhesive.
How do I install a shower pan liner DIY?
After installing the sheets under the toilet in the tiny house I had to install the shower pan liner. The shower pan liner is the water proof layer that is installed under the shower flange and mortar bed. The shower pan liner is extremely important as it is the protection from shower water getting onto the wood subfloor that can rot.
Shower pan liner
Laying a shower pan liner is an art form for sure. You want to be very careful there are no ways for water to escape the area of the pan liner. Make sure the liner is cut to a size that is appropriate to the space but don’t make any additional penetrations. Push the liner to lay flat on all areas of the shower and nail into place. Leave 4” of liner on all sides to go up the edge of the wall. Use red guard water sealer on any areas that are near the shower liner.
Important note: build a small bathroom DIY
The most tricky part of laying a pan liner is setting it up with the shower flange. The pan liner will lay over the flange with the clamping ring of the flange installed over the liner. This will ensure the area where the drain is located will be water tight.
How do I lay a mortar bed for a mosaic tile shower?
The mortar bed will be laid over the shower pan liner that will act as the surface for tile to sit on. I wanted to make sure my mortar bed was laid in a way that created a slope to the drain spout on all sides and was smooth enough to lay pieces for a mosaic tiles.
I set the drain spout into the flange and adjusted its height to where I wanted it. My goal was to have the drain spout at the lowest point in the room. I used an Oatley drain flange that allowed adjustment by screwing it in or out.
How do I create a slope on my mortar bed?
You want to create a slope that is 3/4 inch drop per foot of distance. The distance between my drain spout and the wall was 1.5 feet so I knew I needed a 1.125 (1.5x.75) inch drop at least. The edge of the shower wall was 3 inches tall so this would mean I would set my drain at 1.875 off the ground.
Mortar mix is a concrete that is designed for building shower pans. Mix the mortar in a bucket with water to the consistency of peanut butter. Start by laying clumps of mortar mix on the perimeter of the shower pan liner. Smooth our your work with a trowel as you go. Create another ring in from the perimeter that is slightly lower. Make rings of mortar inward towards the drain spout descending a tiny bit every time.
Tamp down the mortar
After filling the shower pan with mortar use your trowel and tamp to smooth out and tamp down the surface. The mortar should run at an angle from the walls to the edge of the shower drain. Let the mortar set for 24 hours before walking on it. You may need to come in the next day and touch up spots that need more mortar.
How do you tile under a toilet?
In the tiny house bathroom and garage bathroom the area under the toilet was the durock sheets I laid. This area was flat and would be able to have normal large tiles installed on them. I kept the mosaic style by having multiple different tiles. For waterproofing I applied red guard to the durock under the toilets before tiling.
Then I laid the tiles on this durock surface with tile adhesive and let it dry. For both the tiny house and garage bathroom the tile that was directly under the toilet needed to have a hole cut in it for the toilet flange. I used an angle grinder with a masonry blade to make the cut.
How did I tile the walls in the tiny house bathroom?
In the tiny house bathroom I chose to not tile all the way up the walls. Instead I installed footer tiles near the floor that would serve to catch splashing water from the shower. My footer tiles extend up 1.5 foot off the ground of the shower so that water is caught and redirected. The footer tiles were arranged in a mosaic style to match the style of the planned bathroom floor. I installed the footer tiles on to durock pieces that I cut to size. I screwed in the durock and covered it with red guard.
Other surfaces in the shower area like wood or walls have been coated with multiple layers of oil based sealer to protect against water damage. I caulked the edges with silicone grout to make everything look smooth.
How did I tile the walls in the garage bathroom?
The tiling in this bathroom was rather standard as it was built off of a pre made 3×3 shower pan. The shower pan itself was level so I just needed to tile up from there. I decided to tile all the way up to the ceiling to contain steam moisture.
How do you build a mosaic bathroom floor?
I built a mosaic for the shower in the tiny house and also built a mosaic for the floor in the garage bathroom. Before building the mosaic you must decide what colors you want to include. You will take old tile and break it into pieces and then puzzle the broken pieces to create the mosaic. I also did an inventory of all of my left over tile from old projects to see what I had readily available. Another good source for tile material is to use colorful old ceramic plates as pieces in the mosaic.
My bathroom
I had a ton of left over white and gray tile so I knew those would be the good neutral base colors of the mosaics. In the garage bathroom I chose to go with a simple all white tile mosaic because this matched the rest of the bathroom. The main colors of the tiny house were blue and green so I knew I needed to incorporate those into the design of the tiny house bathroom. There was also pop colors of red, yellow and purple that played off other pop colors in the tiny house.
What tiles did I use to build a small bathroom?
I used gray, white, yellow and blue left over tiles from other projects. The purple and red colors from ceramic plates I was able to acquire for really cheap. Before installation I took the tiles and broke them up until the pieces were roughly a few inches in size. You can make your pieces bigger or smaller just understand the smaller your pieces the more work to glue more pieces.
Use a hammer wrapped in a towel to brake the tile and contain dust. Using a tile sanding stone sand the edges of the tile mosaic pieces to make sure they are smooth to stand on.
How do I lay out a tile mosaic floor to build a small bathroom?
It helps to lay out the mosaic pieces on the floor in the shape of the bathroom so you can plan ahead what it will look like. This will allow you to be organized when it comes time to glue pieces. Measure the space of the bathroom then make sure your layout mock up is the same size. In the tiny house I decided to have the tile of my bathroom extend into the kitchen area. This would help with containing water when I exited the bathroom after a shower. In the garage bathroom the mosaic was smaller and just the area under the sink.
Start gluing the pieces with tile adhesive starting with the back row and working your way forward. Make sure the pieces are glued flat and creates a smooth surface with the pieces next to it. I left a quarter inch of space between each tile for the grout. You can choose more or less space than this. For the shower drain the tile pieces should overlay the drain.
How do I grout the bathroom?
After letting the tile adhesive dry for 24 hours I was ready for grouting the tiles. I chose a dark gray grout to compliment the gray of the tiles. Grout comes in a bag and needs to be mixed with water to the consistency of peanut butter. Dark colored grout is a good choice as grout gets darker over time. I used trowel to spread the grout to the area and a grout float tool to smooth the grout into the gaps between tiles.
How did I start grouting?
I had to grout the tiles under the toilet, the mosaic and the footer tiles up the walls for the shower. After applying grout to an area I used a sponge and a bucket of water to wipe off the excess grout. You don’t want to skip wiping excess grout because if you let it dry it will be a major pain to remove. Make sure everything looks good because after it dries its hard to fix.
I worked my way from the back of the bathroom until I got to the front area outside the bathroom. Let the grout dry for 24 hours then go over the grout with 5 coats of grout sealer to protect it.
How do I choose a door when I build a small bathroom?
I chose to fix up a folding wood door with glass inserts in it. My plan was to stain the glass parts to add more light and color to the house. I acquired the door before I framed the doorway so that way I could have the door custom fit the opening. The wood parts of the door were painted white and I stained the glass multiple different colors to match the colors of the house.
To make the wood door water proof I added multiple layers of oil based sealed to protect the door from rot. I had a left over crystal door handle that I installed on the door to replace the old handle.
How do I add lighting to a small bathroom?
I wanted the lighting in my small bathrooms to be effective for the space. For both of the garage and tiny house bathroom I chose a light fan combo that would illuminate the space but also eliminate excess moisture from the room. The shower light fan sits above the shower head and has a vent that pushed the water vapor outside.
What I hired out
I hired out for electrical wiring of the house and had the electrician mount the light on the ceiling of the bathroom. From there I drilled a hole in the side of the house the diameter of a metal vent tube. I connected the metal vent tube to the light and fastened it down with circular clamps. The outside vent attached to the metal siding of my house. I finished off the installation with spray foam to fill the gap where I drilled the hole.
What are the finishing touches to build a small bathroom?
In the garage bathroom I added a multicolor mirror over the sink area. For towel hooks in the garage I used old hose faucet knobs and a bathtub knob to add an extra detail. To compliment the jackson pollock theme of the mirror and shower curtain I hung up old painting palettes from the wall to add some more color. A bidet hose is a good choice for when you build a small bathroom as it makes it easier to clean the bathroom when needed.
To save space on storage I built corner shelves made of plywood. The toilet paper holder is made of left over steel pipe fittings that screwed into a steel flange. The trim matches the rest of the house with 1×4 common board painted white.
How did I build towel hooks?
In the tiny house bathroom the towels hanging from long gutter nails from an old project. The nails were placed within the studbay to save the space of hanging towels. The toilet paper holder in the tiny house is a reclaimed commercial grade toilet paper dispenser. This allowed the toilet paper roll to be covered so it wouldn’t attract moisture from the shower.
Conclusion: how to build a small bathroom
Learning how to build a small bathroom can be exciting and rewarding! Finding new ways to make more out of less space. In this post I have listed out my process for building the components of my efficiency bathrooms. These components include shower mosaics, fold away doors, pocket doors, small toilets, small sinks, no sinks, and space efficient towel hooks. These components allow bathrooms to be much smaller than tradition but offer the same utility.
After reading this hopefully I have inspired you to build a small bathroom!
More resources: https://www.thespruce.com/amazing-tiny-house-bathrooms-to-copy-5204302