Hi, sorry for the confusion.

Its more like which one os determined 1st the FFL, SFL or SSL. What do you determine 1st when you design and carrying that over to your working drawings?

Neither do I, as floor finish could change numerous times, and I don't want a hinkey number for my slab, unless we're depressing the slab.

You'd prefer a hinkey number typed into revit?

Yes FFL is on top of any floor finshes ( ceramic tile, wood flooring, vinyl floor, granite stone, pavers, etc.)

This is (in my experience) a holdover from CAD where there would be real problems if a drafter forgot the minus sign for negative elevations. This is unnecessary in a Revit environment and is a sign that your QA /QM department is from the hand drafting / CAD generation.

Also a sign that the American government messed up when the rest of the world was switching to metric and they failed. Now as a Canadian I must use imperial.......

As a Canadian I think we're definitely all good with both, no?

I fail to see how switching to metric would avoid an error involving the minus sign unless metric doesn't have negative numbers?

Canada uses both units. I had to get used to using the hard neasurement from the soft mesurement. I notice Canadians like imperial and converting it to metric. That is why sometimes.I get a 395mm thk wall or 153mm studs.

TOS is for the Structural drawings. Arch sheets reference FFL. Of course, the nice thing about standards is that there are so many to choose from...

Thanks for the info

Can you ellaborate what are those variables that would affect the design, working drawings or constructability of it?

I've always used TOS on my architectural drawings. Then I give dimensions to things like grab bars as "AFF" - above finish floor. I don't think I've ever used FFL.

Thank you, Donna Sink for the input.

Variables could be: 1) room function changes, 2) slab depressions, 3) transitions between finish material, etc. Say a building section drawing cuts through multiple finish types, does adding 4-5 spot elevations clarify or confuse the reader? Can that info be presented better elsewhere? As Donna alluded to, the more detailed the drawing, the more "real" the dimensions. In our sets, we use TOS throughout as the benchmark (plans, sections, elevations) and then reference "AFF" to indicate hold dimensions for ADA things, etc.

I totally agree with you. I am an architect. For me, when architects do their designs and working drawings, I always think about the 3 items - design, conteact docs and workmanship/constructability. I hate it when architects/ designers tell me that we can make correction or notes on shop drawings to figure out the proper details. Unless the contractor proposes an alternative detail due to site conditions or work around to make the detail more effective or simplifying the details, I find correcting details on shop drawings is a waste for effort and
resources.

And if the contractor was on the design team I may give half a shit. ;)

@SneakyPeteI believe you are refering to "those" contractors. Dealt with them before. Bad habbits, or shall I say, Bad practice dies hard. @atelier nobody, I think there's a grey area to adding notes on shop drawings or submittals. In the door or window schedule, we always indicate the size of the item. And if the wall section and interior elevations shows SSL or SFL, the builder and the supplier will give you according to whatever information that is in the contract docs. A change in dimension due to the point of referenece during installation usually ask a change directive. Notes on shop drawings are only additional comments to the contract docs and usually a cause of many e-mails
during CA stage.

This wall of text creams to me: "lack of construction experience".

You need to consider the sequencing of construction when establishing your levels. Structure will always come first since it gets installed before the finishes - obviously - so you can't expect your formwork trade or carpenter to check your finishes schedule to gauge the thickness of finish. It is your responsibility as the designer/architect to ensure that once your finishes are installed that the resulting space is acceptable and coordinate with your structural consultants accordingly.

creams to me?

^Ha...

I agree that the Structure gets built 1st before installing the finishes. True, the surveyor who set the levels in the site, sets his point/ stakes based on the structural levels but this is not the case in design. When you start a design and putting that in working drawings, architects use FFL as the basis in designing a structure structure or the interior space.  Thus the architects level usually sets what the SSL should be and this will be reflected to the structural drawings  where the surveyor uses in staking out.


FYI, I am very well versed with the processes in constructing a building as I've worked for a GC doing a design-build for years before I join the Archi firm; and took part in planning and execution of various trades from the start of the construction up to the turn-over of the project. So far, that has been the process I've been working on site and in the design office.

Non Sequitor also steals all of the contractors calculators before they start.

Jen C, the assumptions you've stated are not typical as I, an architect well versed in design and construction admin, never start any design as you've stated.

Yes, your assumptions, based as they are in your experience, are not typical whereas Non's, based as they are in his, are typical. See the difference?

^Hey now... don't take away our fun

@non sequitur, I worked as a CA also :) so are you saying that when you determine the bldg 1st floor level from the street level ,as required by code, you basically used or reference with SSL? And if it gets finished with 25mm thk finish, what happen to your compliance? It is something I have to get used to.

Jen, floors don't have to align to street level. We have grading plans and landscaping that bridge the gap between finished floor elevation at the door threshold and whatever elevation the sidewalk (for example) is at. You can't expect that level of precision.

I hear you Non, about sequencing, but: I always give horizontal dimensions to FACE of wall not structure, because I care about the finish space/clearance and I figure the contractor is better at subtracting gyp board thickness/stud actual dimensions than I am as s/he uses them all day.

We actually have the opposite view Donna. We dimension to face of stud (top and left) in new construction because the contractors suck as doing math.

Donna & Chad, I do both (C/L of stud in my case), depending on what I'm trying to convey. Our GC actually get super pissy when dimensions are not to grids tho.

Dims to interior grids are an odd thing. In new construction they can be really helpful to establish a base line to measure from. Exterior grids can be a PITA to measure from in the field. I say we make a surveyor come in a plot all the corners of the stud walls. 8-)

@non sequitur, sorry for the confusion. What I meant was if the 1st floor is a few mm higher than the street level ( being the datum point or the reference grade . I think there's a certain distance from street level/established grade to the "1st storey" level to call it 1st Storey according to the bldg code. I think it was 2m max above the established grade.

Anyways, based on the established grade, you measure your 1st Storey floor level from the established grade to SSL? As for the acceptable tolerances, there is a level of precision that the Architects expect from the contractors. In the construction industry, it is usually 6 to 10 mm difference from the original level. Some countries who use 13mm as an acceptable tolerance in construction.

@Donna and Chad, for interior fitouts, I use the finished wall to finished wall dimension like Donna. The reason being is that, in the case of interior partitions, I like to show the required interior clearance of a room or required clearance of a corridor. On the other hand, for new constructon, I do both - CL of stud and show finish to finish wall dimension for areas where certain clearances are required.

We geolocate our Revit models & so FF is at whatever it actually is above sea level (aka Survey Point. Project Base Point usually puts Level 1 FF at 0'-0"). 

100'-0" is a vestige of the CAD Old Days. Time to let it go.

We do the exact same thing as you do, we just use 100'-0" as our base elevation callout. I have no preference in what way we call the base elevation out - I see positives and negatives in using both. I will say that I've seen drawings as far back as the 30's use 100'-0" as the base elevation. It's not necessarily a vestige of the old CAD days. 100'-0" was used way back because it was more readable and 0'-0"

It was used so that if the minus sign was forgotten or missing, there would be no issue. BIM cannot forget the minus sign and few sets are reproduced via photocopy, so degradation over multiple duplications is not really an issue.

Makes sense why I've seen it with the 100'-0" base elevation in drawings over 90 years old. Those old reproduction methods could miss a lot.

RO for me. While I get it why some uses the Opening CL.

RO for me too. We don't to much residential work.

Center.

Donna, do you do a lot of wood framed construction?

Center of opening in wood framing, R/O for openings in masonry