[somerbuilder]

IRC Code 305.1 dictates: "A shower or tub equipped with a showerhead shall have a minimum ceiling height of 6'8" above a minimum area of 30" by 30" at the showerhead"

Does it logically also follow that once you get 30" away from the showerhead, the ceiling can be lower? I want to put some HVAC ducts above the tub on the opposite side of the shower head.

 

[CarpenterSFO]

Yes, but....

The purpose of that code is not to allow you to build a ceiling lower, but to require you to put the shower-head area in a high-enough part of a room with a sloped ceiling (all the rest of the code about 7' ceilings, slopes, etc.). In other words, you can't shove a shower head under the low end of an otherwise legal sloped ceiling. It is a restrictive exception, not a permissive one.

Can you make the ceiling in the rest of the shower lower? Yes, if it and the rest of the room comply with the rest of the code about ceiling heights. It would depend on whether you're shoving a head-banging vent in there or just continuing the slope of the ceiling, as allowed by code.

That's the gist of a conversation I had with an inspector about this. ScipioAfricanus can probably answer this with greater certainty, based on greater expertise.

 

[somerbuilder]

This is not a sloped ceiling situation. The HVAC duct has to come from an adjacent chase over the tub and into the bedroom on the other side of the wall. This is a remodel not new construction, so things are more tricky, I'm trying to design it with minimal reworking of the floorplan.

The ceiling height is ~88" from unfinished plywood floor to drywall ceiling. Hopefully if I can get a 4-6" tall rectangular duct, then after I add the framing and drywall below it, I can stay above 80" and make the point moot.

 

[CarpenterSFO]

This is not a sloped ceiling situation. The HVAC duct has to come from an adjacent chase over the tub and into the bedroom on the other side of the wall. This is a remodel not new construction, so things are more tricky, I'm trying to design it with minimal reworking of the floorplan.

The ceiling height is ~88" from unfinished plywood floor to drywall ceiling. Hopefully if I can get a 4-6" tall rectangular duct, then after I add the framing and drywall below it, I can stay above 80" and make the point moot.

I don't think that officially makes the point moot. Bathroom ceilings are supposed to be 7' high. The fact that you're allowed to have the area under the shower head lower doesn't give you any license to lower the rest of the ceiling in the shower below 7', unless you comply with the rest of the rules about ceiling height code (i.e. slope). You're probably fine, but I can imagine an inspector telling you to slope the ceiling rather than leave a head-banging edge.

Real-world, many inspectors might be OK with the full shower area at 80", of course.

 

[ScipioAfricanus]

Bob is dead on as usual, if this is a basement situation then the code allows for the duct or beam to be at 6'-4". Don't know if that is the situation you have or not though.
It does't sound like you are trying to lower the entire ceiling though, just a part of it for the ducting. This is allowed to go to 6'-8" for a legal bathroom (min. 50% of room area at 7' high) with the basement exception.

Andy.

 

[greg24k]

Ceiling in a bathroom must be at least 6'8" inches over bathroom fixtures as well as at the center of the clearance area in front of the fixtures, which ranges from 21” to 24” depending on the fixture type.
In a shower or tub area with a shower-head, there are minimum space requirements, which include a 30 inch x 30 inch area at the shower-head and a ceiling height of no less than 6'8"

 

[somerbuilder]

I don't think that officially makes the point moot. Bathroom ceilings are supposed to be 7' high. The fact that you're allowed to have the area under the shower head lower doesn't give you any license to lower the rest of the ceiling in the shower below 7', unless you comply with the rest of the rules about ceiling height code (i.e. slope). You're probably fine, but I can imagine an inspector telling you to slope the ceiling rather than leave a head-banging edge.

Real-world, many inspectors might be OK with the full shower area at 80", of course.

Hi Bob, can you tell me what code section talks about the slope rules that you think I might be violating? 305.1 #1 I definitely meet the rule that 50% of floor area has height above 7 feet, only the small area above the tub opposite the showerhead will have an HVAC duct. Is the "head banging corner" something that is in the code somewhere too, or is that something at the discretion of the inspector?

 

[CarpenterSFO]

Ceiling in a bathroom must be at least 6'8" inches over bathroom fixtures as well as at the center of the clearance area in front of the fixtures, which ranges from 21” to 24” depending on the fixture type.
In a shower or tub area with a shower-head, there are minimum space requirements, which include a 30 inch x 30 inch area at the shower-head and a ceiling height of no less than 6'8"

My California code book (based on IRC of course) says it has to to be 6'8" in the clearance area, and something like "high enough for the fixture to work properly" in the area over the fixture itself (allowing the area over a toilet for example to be somewhat lower). I could be wrong about that, so I'll check later when I'm back in the office.

Hi Bob, can you tell me what code section talks about the slope rules that you think I might be violating? 305.1 #1 I definitely meet the rule that 50% of floor area has height above 7 feet, only the small area above the tub opposite the showerhead will have an HVAC duct. Is the "head banging corner" something that is in the code somewhere too, or is that something at the discretion of the inspector?

Knowing the details from you, you're probably OK. I was just pointing out that 305.1 doesn't simply allow up to 50% of the ceiling to be lower, or simply allow the other part of the shower to be lower. It makes an exception for ceiling height specifically for sloped ceilings, allowing heights down to 5'. Then it requires heights for specific areas, for example under the shower head and in front of fixtures. In my talk with an inspector about this, the explanation to me was that those 6'8" heights were to be understood in in the context of the rest of the section (sloped ceilings), and that you couldn't for example arbitrarily lower the ceiling over the other end of the bathtub - in the case we were discussing we couldn't just shove the end of the bathtub into a considerably lower alcove.

Again, given the heights you mention, you're probably OK - I'd be surprised if an inspector had any issue with it.

- Bob

Edit: I'm sorry to be so convoluted about my response. Sometimes the answer to the specific situation is simple: "Yes, you can do that," but because we're here on the world wide interweb, and C.T. shows up pretty high when homeowners search for specific answers, it seems important not to be too fuzzy about the code. I'm definitely going to double check my comments this evening.