Gyp Ceiling Revisit

[antman]

This is something I still have not come across a great answer for. As far as I can tell, ceiling tags will list the height of the lowest point of the ceiling. For suspended ceilings this is the preferred result. However, for gypsum board ceilings, which are applied to framing above, this gives a value other than the nominal number we like to show. For example, for a standard 8' ceiling the bottom of framing is at 8', meaning the bottom of gyp is at 7'-11 3/8". In this condition the tag should read 8'-0" since we give dimensions to framing, not to face of finish.

I have learned that a spot elevation tag can list either the bottom or the top of the tagged element. I guess the only drawbacks to this are:
1.) You lose the ability to Tag All
2.) You have to model the framing separate from the finish instead of keeping it as a part of the ceiling family structure. In some cases this is actually ideal, e.g. at ceilings applied to a floor above or the bottom of a truss system. For soffits, however, the work is doubled.

Anyone have some good input as to how these conditions are best handled?

[patricks]

We usually just place the ceiling at 8 feet (lowest point) and the framers can either put the framing at 8 feet to the bottom, or up 5/8" higher. I really don't care as rarely does 5/8" make that much of a difference. I just want my RCP's to not have mass amounts of fractional ceiling heights.

If the height is absolutely critical, then usually there will be some other bold notes to that effect for the critical areas, so again not a big deal.

[antman]

That is what I did. Unfortunately a group of rooms had a mechanical platform over them, so my ceiling and the floor members placed by the structural team were not in agreement. Besides, the whole point of using BIM is that the model represents the built condition. My coworkers and bosses become highly annoyed by my use of fudging something by 0.001" in Revit or ACA just to work around a bug. Five eighths of an inch can turn into a really big deal in many conditions. I would much rather my sections and elevations be accurate than make something wrong just to get a tag to read the number I want it to.

[Dimitri Harvalias]

I think you always need to ask yourself what the critical dimension is. Are you concerned with clear height within the room or are you concerned with clear headroom at the mechanical platform. That will help you determine what the tag should read and how you might want to approach it from a modeling standpoint too.
As for the discrepancy between architectural and structural, if you have a finished ceiling elevation and they have a top of framing elevation then one would hope they'd be different and a contractor worth his salt would cross check (yes, I know, that's in a perfect world and please don't point me to the BIM Lawsuit thread :roll:)

[patricks]

Are you attaching said gyp directly to framing members that have a bearing or top elevation defined on structural drawings? That being the case, I usually use a ceiling tag that says "B.O. Structure" instead of giving a hard elevation number, and it also has a shared parameter that lets me enter a structure height if desired, or I could type "See Struc." or something like that.

[antman]

I think you always need to ask yourself what the critical dimension is. Are you concerned with clear height within the room or are you concerned with clear headroom at the mechanical platform. That will help you determine what the tag should read and how you might want to approach it from a modeling standpoint too.
As for the discrepancy between architectural and structural, if you have a finished ceiling elevation and they have a top of framing elevation then one would hope they'd be different and a contractor worth his salt would cross check (yes, I know, that's in a perfect world and please don't point me to the BIM Lawsuit thread :roll:)

In this case, the critical dimension is the correct one. The disconnect, however, is that the industry standard is to display the nominal height in this condition. All I really want is for the tag to be able to read the way I want.

How about this for an idea:
In the ceiling family, add two radio buttons for each layer (top and bottom of layer) and define what value gets tagged.
-or-
In the tag family, be able to specify which height of the ceiling is looked at for the value:
Top of finish
Top of core
Bottom of core
Bottom of finish
I think I like this option better, and with a little programming knowledge could probably make it happen.

[sbrown]

All you need is a note on your ceiling plan that says all ceilings are dimensioned(tagged) to finish. Then do your ceiling/soffit details and use the spot annotation to show the framing elevations. Don't worry about messy numbers, contractors can deal with them. If the true finish is at 7'-11 3/8", thats not a problem for them. Anytime dimensions are critical, do a quick detail.

[patricks]

I suspect it's not the complex fractional dimension that I nor the OP is worried about, it's how "messy" it makes a ceiling plan look when you have all those fractions in your tags all over the place.

[antman]

I suspect it's not the complex fractional dimension that I nor the OP is worried about, it's how "messy" it makes a ceiling plan look when you have all those fractions in your tags all over the place.

Yep. That's it. However, after talking to one of our project managers, the tag *should* read the finish height. So technically the framers should be accounting for finish thickness when they do their work. The reality is just that they don't do that unless they are aware that it is a condition that requires the distance to be precise. Guess you learn something every day.

[patricks]

Yep. That's it. However, after talking to one of our project managers, the tag *should* read the finish height. So technically the framers should be accounting for finish thickness when they do their work. The reality is just that they don't do that unless they are aware that it is a condition that requires the distance to be precise. Guess you learn something every day.

In that case, I'd put all your ceilings with the face of finish where they need to be (even 8' - 0" or whatever) and then put a big hairy note on the ceiling plan that all ceiling heights shown are to the face of finish, and of course make sure there's a detail or something that shows how thick that finish is relative to the framing.