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Common Bathroom Floor Plans: Rules of Thumb for Layout

There are a few typical floor plans to consider when designing the layout for a bathroom in your house. These eight lessons illustrate the common plan options and describes the advantages and disadvantages of each. Of course, there are always exceptions, and a good designer can find a solution that meets your needs.

Jeff Pelletier

July 5, 2019

I’ve been in enough homes over the years to observe that designing and laying out a bathroom is apparently a tough nut to crack for a lot of American production builders. Weird-shaped rooms; angled tubs, toilets, showers; and generally, spaces that are just plain awkward — these all seem to be hallmarks of poorly-designed bathrooms.

When planning a bathroom (either when building new or remodeling) there are plenty of rules of thumb to follow for bathroom layout. So, in the selfless interest of trying to make the bathrooms of America a little better, read on for some standard rules of bathroom design.

Side Note: This post covers the basics for single-family residential bathroom design. We’ll look at bathrooms with a shower (¾ bath), or bathrooms with a tub (full bath), or even combinations of both. Bathrooms with just a toilet and a sink, known as powder rooms, are a different animal altogether, and not covered in this post. Also, bathrooms in multifamily buildings (like apartments) are a whole different ballgame due to accessibility rules. (If you'd like to learn more about either of these, let us know, we’d be happy to elaborate in a new post!)

Rules of Thumb for Bathroom Design

Lesson 1: Start with the Basics

This is the good old “three-in-a-row” bathroom we’ve all seen. It is around 40 square feet (5’ x 8’) and here are the typical rules of thumb for how it works.

This is an efficient bathroom, and, it just plain works. There’s an efficiency in plumbing cost, as all the plumbing is on one wall. However, that efficiency comes with the downside that the room isn’t all that special, and it has limited counter space. Still, it is a classic and always a bathroom powerhouse. And — wow — I just typed the phrase “bathroom powerhouse” — I’m checking off life milestones left and right today.

The other tweak to this one is the “banjo” top which has a smaller countertop extension above the toilet. I’ll be honest, I don’t love it, but I understand the value, and it can sometimes be a good solution. I won’t hate on you for going down this road, I promise.

Lesson 2: A Better Three-in-a-Row

With this plan, you commit to the idea of one plumbing wall, but then extend the bathroom (and hopefully widen it) a bit. You can easily get two nice sinks in a more public area, and then have a pocket door into a toilet and bath/shower room. This allows for two people to use this bathroom at once — making it great for a shared kid’s bathroom — with some built-in privacy.

Conversely, this can also serve as a bathroom that does double duty as a full guest bath or a powder room.

Put the sink and toilet in the room off the hall, and then have a door into the shower room beyond. I find it a little odd, but it is definitely a solution for someone who wants a room that looks like a powder room, yet has the ability to handle the occasional showering guests.

Lesson 3: The Opposite Wall Bathroom

From a space point of view, this one usually takes up more room — but — it provides a far more generous layout. It will cost more, as there’s more plumbing work and overall square footage, but it provides flexibility for how the space is used.

There are variants from small to large here. You can also modify the same 5’ x 8’ footprint that is in the classic three-in-a-row and go “opposite-wall” here, but I think you end up with higher plumbing costs and not that much better of a bathroom. I think this works best when you have a little more room.

Lesson 4: The Hotel Special

Here’s a tough one: I understand the benefits of this, but I personally can’t stand it. Hotels have found that the standard three-in-a-row is pretty drab and has limited counter space. So, they took the same footprint as the three-in-a-row and put the countertop across the wall, opposite the tub.

Plenty of counter space, sure, but it means you have to put the toilet precisely in the floor space that you’d need to actually take advantage of that counter; and, the toilet is in full view through that open door. Good luck easily opening the bathroom door; or, having more than one person in there at once. Use this layout only if countertop space is your absolute must.

Lesson 5: The Compact, Five-Piece Master

Master bathrooms tend to have two sinks, a toilet room, and a shower. Bathtubs are something that I only recommend if you know you’re going to use it, or if it really suits the space. Sometimes, though, you’ll want one — and, so, how can you efficiently lay one out?

Here is an efficient way to get all of those program elements into an 8’ x 12’ space (less than 100 square feet). This gives you options for door layouts and for window locations, as well. If you want to add some extra space to this, you can easily pull the tub into a wider space and have it be free-standing.

Lesson 6: The Shub

This is a hot topic in our office (!!). People divide into factions of either "pro-shub" or "anti-shub" — wait, you probably have no idea what a “shub” is, do you? Here at Board & Vellum, we’ve coined the portmanteau, shub, to cover the situation when a shower contains a tub. Fans of this point to the compact design and the general aesthetic, and detractors think you’ll be freezing cold in a big open shower and can’t imagine how you can clean around a free-standing tub. Regardless of how you feel, here’s how it generally can lay out.

The benefit is, you can get down to a 6’ wide space (or even 5’ if you’re OK with a cozier space) — but really, that’s a little insane. It can be as short as 12’ (although only with one sink), or if you can tuck the toilet off in a separate room (ideal) it’ll work better. You see these frequently in townhome designs, as space is at a premium. Personally, I think if you’re down with the realities of what a shub means, then I’m here for you. Just don’t ask Sara in our office what she thinks. ;-)

Lesson 7: The Small, Square Bathroom You’ve All Seen

I hate this bathroom. There, I said it. I just do not like corner showers.

Some people may like corner showers; and, well, that’s fine for them. But I’m writing this, so I’m here to tell you that this bathroom is just rough. It feels tiny. But if you’re curious how it lays out, there you go.

Lesson 8: The Super-Tiny Bathroom That I Don’t Hate

I’ve written about this before, and there are lots of tips to getting it right.

But here’s a compact way to get in a real ¾ bathroom without too much pain.

Lesson 9: There’s Always an Exception

For every rule of thumb described above, there’s always a bathroom that we approach that has some weird exception that simply doesn't fit into these rules. A good designer will be able to help fit a comfortable (and not odd) bathroom layout into even a strange space. You can sneak a long counter under a sloping roof; or, deal with a window right where you want your mirror, or even tuck an attic access hatch behind a tub.

Design is an exercise in understanding the rules of thumb and then building or expanding upon them to create something great. Push the limits of what your bathroom can be, and make it better than the vast majority of bathrooms out there!

Common Codes for Bathroom Design

In the interest of providing some more rules of thumb, here are some common codes and typical dimensions to consider:

• A normal tub is 2’-6” by 5’-0”. However, you can get ones wider — 3’ is common, and a shorter 4’-6” is common enough. For a soaking tub, you’ll want at least a footprint of 3’ x 6’ (although some vessel tubs can be smaller or more compact).

• A good two-person shower is 3’ x 6’. A nice one person shower is 3’-6” square. Technically, a shower only needs to be 2’-6” in each dimension. That’s only “fine,” in my opinion, when the other length is at least 3’, so you can raise your arms to wash your hair easily.

• For a single family residential application, you only need 2’-6” of width to fit a toilet. If you have accessibility concerns, then bump this to 3’ wide.

• A wall-hung toilet can save you about a foot in floor space. I love toilet rooms that are 2’-8” to 3’ wide, by 4’-0” long, with a wall-hung toilet on the short dimension.

• A double vanity for a master bathroom can be as narrow as 5’. Even so, you’ll see narrower ones at places like IKEA, but I think they’re a touch too tight. You can sometimes get away with one trough sink (with two wall-mounted faucets), but ideally, is at least 6’ wide.

• Bathrooms designed for aging in place, or for people who need grab bars or more accessible design, warrant more room in almost every direction. While all of these layouts can be modified, the classic three-in-a-row is the hardest to make truly accessible.

So there you have it, a barebones lesson on basics bathroom design. Laying out a bathroom is one of the most rewarding parts of my job, and if this helps reduce the amount of new sad bathrooms being built, then I’ll be a happy man.