There is no rule, however 3x5 is not large enough to go without a door. You will have water everywhere. The smallest shower we have done without a door was 42" x 7'. We had a 32" opening without a door for accessibility and the owner still complained that water escaped the shower.

Can you draw a sketch of which way the opening would be? I think you can have a doorless, but what you want is for the opening and the shower head to be on the same wall. So, doorway 30" (you can do less if you aren't worried about getting a wheelchair in there) and 30" with the showerhead centered on it. The water will if anything hit the 5' wall 3' behind you.

I had a 4x6 shower. My door opening was about 26" ( a bit smaller than I planned, not ideal). The shower head was on that wall, spraying towards the long back wall. My shower had a 1.5" curb. Never had water outside (well, until you leave the shower, obviously) :)

Now, if i had put the shower head on the shorter side and sprayed towards the door, would have been a different story, in fact, it was plumbed wrong initially and I had them fix it.

Flo - we live in a warm area so I'm not too worried about the cold. I HATE cleaning glass...and we often keep our house pretty warm 82F...so mold/nasty shower door are more of a concern than a cool breeze. We do plan a small curb and center drain. I have always had tiny showers with doors, so the potential of an open shower is appealing.

mimimomy - thank you for sharing your experience! hmmmm....I don't love the idea of standing on the open side and showering... Will definitely be thinking on this.

Well really you aren't in the open. You would have a 3 sided enclosure of about 32"x36"x60" .... so your typical corner shower is shower is 32 to 36" square. Your doorway would be about a 28" opening on the 32" wall.... Of course, you have to plan on the partition width for the shower head wall... and your doorway can be slightly smaller.... in our older home there is a 2' doorway into an ensuite bath.

Maybe this will help you visualize. We used to live in Florida and my shower was my favorite room in the house :) It was good I drew this up, as I have been trying to plan a shower in another project I have going, and I am pretty sure this design will work.

Note, put your controls on the opposite side so you don't get wet when turning the shower on.

Well having had a very similar shower, and used it for 15 years on a daily basis, I'm pretty confident it won't (but I could be wrong). I would personally make the doorway about 24" if I wasn't worried about using it for disability access. I'd certainly try it first, and if it didn't work, add the door later.

I did not have a super high spray, and don't want one, so maybe that's a factor? My shower right now primarily sprays straight downwards.

I think we will give it a go with the thought that adding a door might happen. We will be putting the shower head on the short wall away from the door. Controls also. Doors happen at the very end anyway, so that is good. This bathroom will be likely put off until we move in and finish some other necessities. We will share with the kids for awhile. I am just planning right now.

Next time you take a shower, lay newspapers on the bathroom floor and leave the door/curtain open during the shower. After the shower make note of where the newspapers got wet. This will give you a good idea of the size of a doorless shower or where walls have to go.

Mark - we are currently using a FEMA trailer to shower (or the gym if I want a long hot shower). No way to test right now. I will try this when we get some plumbing and the kids shower up and running.

Oh, and in case it isn't clear in the diagram, the entire area must be tiled/solid surfaced, as the water will be primarily be hitting the 5' backwall.

I may be building this in the next few months, and if so, will let you know my results. :)