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Ceiling Height/Top Plate deviation

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  • PatrickGSR94
    replied
    1/2" GB ceiling applied to 3/4" furring strips like 1x3's or 1x4's is pretty common. That's 1.25".

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  • cellophane
    replied
    Originally posted by MPwuzhere View Post
    How do you get 1.25" difference? 5/8" Sheathing over 5/8" Gyp? Thought most homes the gyp bd is attached directly to the trusses so a 12' ceiling is in reality 11'-3/8"?
    1/2" GWB is typical in residential (IRC)
    5/8" GWB is typical in commercial (IBC)
    a lot of rated assemblies require metal furring / resilient channel in addition to the gyp which adds an extra 1/2" - 7/8"

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  • PatrickGSR94
    replied
    As far as the ceiling tag goes, if the finish is really applied directly to the structure, as is the case in most residential construction, or some light commercial wood-frame construction, I just use a ceiling tag that has the type mark and then "B.O. Structure". Bottom of Structure. No need to list the height since the ceiling installer doesn't have to measure the height. He just puts the gyp directly up to the truss or joist. I prefer this over having long, strung out ceiling height dimensions in my tag i.e. 11'-10 1/2" no thank you. That takes up way too much room on my ceiling plans.

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  • Charles Karl
    replied
    AFF seems to have morphed into a nominal term similar to 2x4. In any event, a contractor knows what needs to be done and will install ceilings using accepted construction tolerances.

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  • MPwuzhere
    replied
    How do you get 1.25" difference? 5/8" Sheathing over 5/8" Gyp? Thought most homes the gyp bd is attached directly to the trusses so a 12' ceiling is in reality 11'-3/8"?

    Leave a comment:


  • Twiceroadsfool
    replied
    Its an issue on Concrete and Metal Pan, because of how we tend to model and document finishes. For us, at least. We model Slabs down from the level, and finishes up. So the ceiling height is NEVER "AFF." Its "above the level."

    We had to have ALL KINDS of meetings about this recently, because a lot of architects just get in the habit of writing "AFF" and then we have to explain: Well, okay, but were going to RFI just about every concrete section, floor transition, and so on. Because of things are marked as AFF, and the finishes are all assumed to be flat, flush, and level, its a BIG change to a lot of the concrete work... All over a note that doesnt even need to be present.

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  • cellophane
    replied
    Originally posted by Twiceroadsfool View Post
    The project im working on right now had quite a big issue, over certain items being marked as "AFF" even though they were tagged off the level. With various finish thicknesses on the floors, it created some pretty decent complexities, concrete work wise. And for what? Because weve always tagged things as "AFF?"

    If you REALLY need that ceiling to be held at exactly 12', then raise it up to be at 12'. If its as Cellophane said, level it at 11'-10 3/4". And in BOTH cases, make sure your Legends and notes stipulate that its above the LEVEL (as the tag works), unless you are putting in LEVELS at every finish (yikes).
    That is a fantastic point, and not just in terms of modeling & legends. From a practical standpoint / order of installation, the ceiling is almost always installed way before the finish floors are, and usually before any gypcrete is installed. If floors are concrete in a metal pan it isn't quite as relevant but the wood assemblies we use all use gypcrete on top of the sheathing (UL L506 or similar) which means there is an additional 3/4" - 1" difference in the tagged value and installation time value.

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  • Twiceroadsfool
    replied
    Originally posted by cellophane View Post
    I'd just leave the ceiling tag at 11'-10 3/4". That is the ceiling height. We do a lot of wood frame stuff where the ceiling is attached to the trusses and unless someone wants or needs an actual 12'-0" ceiling the heights always end up a little weird. Personally I'd rather have clean framing dimensions because in reality - the GWB installer is installing on the framing, they don't really care about the height in that case.
    This.

    And my ONLY other comment on the subject is: When we develop our modeling standards and annotation standards, we need to be a little more practical about how we model and tag things, and what those values represent.

    The project im working on right now had quite a big issue, over certain items being marked as "AFF" even though they were tagged off the level. With various finish thicknesses on the floors, it created some pretty decent complexities, concrete work wise. And for what? Because weve always tagged things as "AFF?"

    If you REALLY need that ceiling to be held at exactly 12', then raise it up to be at 12'. If its as Cellophane said, level it at 11'-10 3/4". And in BOTH cases, make sure your Legends and notes stipulate that its above the LEVEL (as the tag works), unless you are putting in LEVELS at every finish (yikes).

    And- again- if you need more height, just raise it up and let the tag read what the tag reads.

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  • cellophane
    replied
    I'd just leave the ceiling tag at 11'-10 3/4". That is the ceiling height. We do a lot of wood frame stuff where the ceiling is attached to the trusses and unless someone wants or needs an actual 12'-0" ceiling the heights always end up a little weird. Personally I'd rather have clean framing dimensions because in reality - the GWB installer is installing on the framing, they don't really care about the height in that case.

    Leave a comment:


  • chris.macko
    replied
    If it's only 1 story you could try spot elevations with the top surface targeted. Ceiling tags are only going to give you the offset of the ceiling. Over here a 12' ceiling is actually 12' to the bottom of the ceiling, but then these are usually suspended ACT or GYP, and never wood framing.

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