What size black porcelain are you thinking of? I can't picture what you mean by "black and white mosaic dots". Do you have any photos of your choices?

I've seen black porcelain hex tiles and penny rounds used on shower floors in baths with similar design elements to yours, but not a large-format slate-look porcelain. Normally that would be used on the main floor and something smaller with lots of grout lines for shower floor.

I have 12x24 slate-look porcelain with carrera hex tile on shower floor+ white subway shower walls. Sort of sleek yet vintage-y for our old house.

I could see that working but I haven't seen any examples of it. This is a picture of a solid piece of soapstone. I can picture it with smaller tile on the main part of the floor.

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by Ottawa Tile, Stone & Countertops Canadian Soapstoneâ¢

A couple of things to consider:

It may not be a good idea to put the subway tile on the top of the curb. A solid surface threshold will be less likely to leak, crack and last longer.

Most often the smaller tiles are used in shower floors because they conform more easily to a slope with fewer cuts and there is more grout which helps make it less slippery.

Maybe consider using the basketweave both inside and outside the shower and use a black stone/solid surface piece for the threshold. That might give it more of an art deco look than you're going for though.

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by Memphis Interior Designers & Decorators Anna Baskin Lattimore Design

This picture has a combination of basketweave, large tile and subway. I like it!

Thanks shanghaimom and lotteryticket! I was thinking of small square black porcelain slate for the shower floor, not big tiles. Shanghai, the mosaic I mentioned is a 5 row black/white checkerboard that would be an accent on the shower wall and in niche.

I saw a beautiful basket weave tile at Best Tile that is the reverse of what we're using on the main floor (ie, black with white squares) and can't let go of the idea of that for the shower floor, but it's waaay too expensive - the black slate look porcelain idea is aimed at getting the contrast without breaking the bank...

I think it'd look fine.

I do have a photo of Continental Slate Asian Black on a shower floor. I cut the 12's into about 4" squares.

No grout, just tile:

After grouting:

Thats a pretty nice floor Mongo :)

Why thank you Enduring!

That shower was different than any other shower I've ever done in that the tile was already bought, and I had to only use the tile on hand. X boxes of the wall tile and Y boxes of the Asian Black. All were square tiles.

There wasn't enough wall tile to do the walls and there was no way to source any more of it. So I had to fudge the design and add a little asian black where it sort of made sense to do so.

There's not a single uncut tile in that entire shower. Walls, floor or ceiling. When I was done I literally had a handful of scrap offcuts left over.

And it was for a magazine shoot to boot!

Never again! lol

And for the original poster: The reason I included the ungrouted photo is it shows what the floor "sort of" could look like with a dark gray or a charcoal or black grout. You can see how the floor sort of harmonizes or blends into "just a floor".

The light grout on dark tile? The contrast accentuates the geometry of the tile and makes the tile pop.

Different effects.

Wow - I really like that floor, Mongo, in both photos! So now I know a black porcelain 'slate' floor can look great, I just have to decide whether it will look great next to a basket weave floor. Suggestions on grout if we do that pairing (and with white subways on the shower wall)? I'm thinking darker grout - but I could easily be convinced that lighter would be better.

Thanks!!

"I'm thinking darker grout - but I could easily be convinced that lighter would be better."

If you are thinking dark grout with the basketweave...

I find that combination (charcoal or dark grout and basketweave) to be stunning. It really makes the pattern pop. Here's a nice contrasting shot with both options:

{{gwi:1491723}}

Although the following are marble basketweaves, the "light grout" photo is simply the tile ungrouted. The grouted tile had a dark grout. These are from Casey's bathroom, one of my favorites of all time. Simply stunning.

Ungrouted, giving the illusion of a "light grout look":

And grouted with a dark grout:

I kid you not, that floor gets to me. It's simply spectacular.

I could fully see a bathroom with a basketweave with dark grout, then the shower having dark slate with dark grout. The basketweave with dark grout would be the attention-getter and show-stopper. The slate with dark grout would simply "be there". The dark/dark combo wouldn't pull the eye to the shower floor. It wouldn't try to compete with or distract from the basketweave.

If the slate had light grout, causing the tile pattern to pop, I almost think it would be a detriment to the overall design.

Let the basketweave be the star. Let the shower floor play second fiddle.

Do understand that it simply my opinion, based on how my eye sees things. Certainly feel free to do what pleases you!