http://www.iapmo.org/2013%20California%20Plumbing%20Code/Chapter%2004.pdf

Thanks for the document. I also read pages numbered 54 and 55, it not clear to me how curbless showers are tested, let alone built. Would appreciate any other thoughts you may have.

Thanks for the advice. Will follow-up with your suggestions.

"Is my understanding of the Schluter system incorrect (i.e. the whole bathroom subfloor including the shower area can be level)"

You are incorrect. The floor must be sloped a minimum of 1/4" per foot toward the drain. You will quickly get annoyed if the floor in front of your vanity is sloped.

"it not clear to me how curbless showers are tested, let alone built."

It is tested by filling the 2" or greater depression created by the slope with water. The depression is created by lowering the floor joists, etc as your contractor says.

"Our contractor however says that doing a curbless shower will require different framing (shorter floor joists etc.) so that the actual shower area (before tiling) is slightly lower than the rest of the bathroom floor."

A trench, or line drain is often used at the back of the shower with a 1/2" per foot slope to gain the 2" of vertical drop required within a 4' shower area.

Keep in mind the definition of the word "threshold", as it is often misused in local interpretations of the code. They seem to get it confused with a "curb" just because most thresholds on exterior doors are raised.

http://dictionary.cambridge.org/us/dictionary/english/threshold

A threshold does not have to be a different material than the rest of the floor, or different color, or even a different height from the main part of the bathroom floor. It is merely the part of the floor at the entrance to the shower.

Because of this definition confusion, many of the following links won't make complete sense, or agree with each other even though the code is statewide, and why different cities are coming up with different interpretations of the code, and trying to come up with their own "workarounds". It is essential to know what city is handling the permits, and their interpretation to have a real conversation about this.

http://www.cityofpaloalto.org/civicax/filebank/documents/17795

http://www.countyofnapa.org/WorkArea/DownloadAsset.aspx?id=4294980783

http://www.buildingincalifornia.com/wp-content/uploads/2014/01/CurblessShowerOakland21.pdf 

If some of these links don't work, then a goole search of the link might get a link that should work?

http://webcache.googleusercontent.com/search?q=cache:1Kmtr34BpY0J:www.cityofpaloalto.org/civicax/filebank/documents/17795+california+building+code+curbless+shower&cd=5&hl=en&ct=clnk&gl=us&client=ms-android-verizon

http://webcache.googleusercontent.com/search?q=cache:UcZyMnEHzmoJ:www.countyofnapa.org/WorkArea/DownloadAsset.aspx%3Fid%3D4294980783+california+building+code+curbless+shower&cd=3&hl=en&ct=clnk&gl=us&client=ms-android-verizon

Fred S . to be clear i was not aiming at you! random(speaking in general terms.) myself included.

Its funny how many pictures one can produce on houzz of curbless showers in california that dont come near a 2" drop in elevation from entry to drain. ? hmmmm. a whole other topic.

As to my statement, call youre local inspector first things first, as they can and will trump everything....

-best

The standard is 2% not 2"

bv, could you just put a row of seats in the corner? this is getting good. we need some towels too, think we might be in the splash zone. tehehe

@Tundra, I understood what you meant. I actually started typing my last response before you posted. It was just happening slowly, between interruptions. I think we are both on the same page. I just spent a little time searching for references to show how the "interpretation" of the exact same code is so different in different cities in California even though local "amendments" are not allowed without state approval, and must pertain to local climate and geological type conditions ONLY.....

The same conclusion of "call you're local inspector, first things first" was supposed to be extremely evident after looking at the links I provided ;D

B V there is a lot more detail to consider for a barrier free shower. A center drain will help decrease the drop needed by 50%. as Tundra stated check check with your building inspector first and I agree with the USG system over Schluter. They will custom make your base. Sorry I was typing when Fred posted.

The VIM level entry shower system does not require the floor system (ie. floor joists, trusses, I-Joists) to be lowered in order to achieve level entry into your shower. Our installation video shows how this is achieved and can be viewed at www.vimproducts.com. It can be customized to fit just about any size shower.

The system is code compliant and you are not required to have a threshold on your shower. As far as testing goes, once the water proofing is complete, a temporary threshold can be constructed out of plumbers putty so the system can be flood tested. You will need to fill the system with 2" of water measured at the temporary dam.