I need your opinion on this item. I had a conversation today with colleagues about which Floor Level is the basis in determining the other Levels in a storey. Is it the Finish floor level (FFL) or the Structural Finish Level (SFL) or the Structural Slab Level (SSL)? Correct me if Iam wrong, FFL refers to the level at the top surface of floor finish. This is where all the building element finish levels are referenced from. SFL refers to the level at the top surface of the floor screeding or concrete topping. While SSL refers to the level at the top surface of the structural slab.
Now, when an architect starts to design a storey, which one do you use as your Floor Level? Is it the FFL, SFL or SSL? Also, whichFloor Level serves as the basis of setting the other levels in a storey? Is it SSL is given first then you figure out the SFL then the FFL or the other way around, FFL is set first then the SFL then the SSL?
What are your thoughts on this one? Thanks in advance for sharing.
archeyarch
Jan 15, 20 12:02 am
FFL
b3tadine[sutures]
Jan 15, 20 12:18 am
Are you asking what is 100'-0" or 0'-0"?
Jen_C
Jan 16, 20 2:06 am
Hi, sorry for the confusion.
Jen_C
Jan 16, 20 2:07 am
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?
Non Sequitur
Jan 15, 20 7:07 am
I’m assuming here that FFL includes the thickness of ceramic tile or whatever floor covering. We don’t bother with this and use a top of slab or under side of deck dimension.
This sounds more like a revit level set up question that a CA one.
b3tadine[sutures]
Jan 15, 20 10:54 am
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.
SneakyPete
Jan 15, 20 12:57 pm
You'd prefer a hinkey number typed into revit?
Jen_C
Jan 16, 20 2:09 am
Yes FFL is on top of any floor finshes ( ceramic tile, wood flooring, vinyl floor, granite stone, pavers, etc.)
Almosthip7
Jan 15, 20 11:09 am
We use 100'-0" as top of main floor slab.
SneakyPete
Jan 15, 20 12:56 pm
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.
Almosthip7
Jan 15, 20 1:39 pm
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.......
Bench
Jan 15, 20 1:41 pm
As a Canadian I think we're definitely all good with both, no?
SneakyPete
Jan 15, 20 1:42 pm
I fail to see how switching to metric would avoid an error involving the minus sign unless metric doesn't have negative numbers?
Jen_C
Jan 16, 20 2:12 am
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.
threeohdoor
Jan 15, 20 12:16 pm
TOS is the way to go. FFL is always bound to change and is dependent on too many variables.
tduds
Jan 15, 20 1:48 pm
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...
Jen_C
Jan 16, 20 2:13 am
Thanks for the info
Jen_C
Jan 16, 20 2:15 am
Can you ellaborate what are those variables that would affect the design, working drawings or constructability of it?
Donna Sink
Jan 16, 20 1:09 pm
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.
Jen_C
Jan 16, 20 10:15 pm
Thank you, Donna Sink for the input.
threeohdoor
Jan 17, 20 9:46 am
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.
SneakyPete
Jan 15, 20 12:54 pm
Are you the architect or the structural engineer?
Do you need the fixed level to be the surface that's walked on or the structure that holds it up?
Do you want the level in the model to provide the element least likely to move?
Do you want your contractor to need to do math?
Make a decision. There is not right or wrong. If your priority is FFL, use FFL. If your priority is making the contractor not have to think, use SSL.
My opinion is that we're architects. We care about the finished building. We also work with dozens of intelligent, capable humans who are responsible for their own various portions of the project and don't need crutches. Use finishes for dimensions and make damned sure your details, schedules, and assemblies are dimensionally correct and provide enough information to eliminate possible RFIs.
Jen_C
Jan 16, 20 2:25 am
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.
atelier nobody
Jan 15, 20 2:38 pm
In my experience, whatever we call out, the Contractor actually uses the top of slab as his reference, for everything from floor-to-floor heights to door heights. Based on this, I try to note the drawings clearly that way, and reserve any reference to "finish(ed) floor" for details where it actually matters - then make it very, very clear on the detail that I am pointing to the floor finish, not the slab.
SneakyPete
Jan 15, 20 3:58 pm
And if the contractor was on the design team I may give half a shit. ;)
Jen_C
Jan 16, 20 2:38 am
@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.
Jen_C
Jan 16, 20 2:05 am
Thank you everyone for your comments. This conversation came about when I had a kick off meeting with our team lead. I wanted to find out how he wanted to show the Architect's intent in the drawings so everyone are on the same page. My role in the team was to help out with the production of drawings.
Anyways, this is why I posted this item here to see what is the industry standards here in Canada or US. As the Design Architect or technician, we should be able to communicate or translate the design to working drawings where it would show the clear intent of the design to the persons who are building it. Be it in Revit or CAD or manual drafting.
In past, I've always used FFL (top of the floor finish) as my point of reference to determine the SSL or the underside of joists. I do not even bother thinking about the SFL. This has been my practice and have seen some architects, GC, CM and PM do the same. This process may be different with wood constructon but, most of the time, it can be applied as well.
From my understanding, why FFL is always the point of reference in a storey is due to the following design reasons:
1. Architects mostly deals with the design. How the whole structure interior and exterior would look and function. Also, someone told me, Architects lead the consultant team, therefore, its always the Architect (responsible for the finishes) will dectate the reference based on the top of the any finishes.
2. All of the code requirements regarding minimum and maximum heights and clearnces are based on the finishes and not from the SSL ( Top of Slab) or SFL (Top of floor screeding or concerete topping). An example for this one are the handrails, guard rails, door heights, finished ceilung height and headroom clearances. If all minimum clear heights are reference from SFL or SSL, how would you comply to the minimum requirements when there's about a 25mm difference between the SSL and the FFL? How are your door panels going to look? Are the door panels going to have various heights due to different floor finish thicknesses while maintaining the industry standard gap requirement for doors? A ceiling height of 8' is not a true 8' at a granite floor finished area compared to the ceiling height at the exposed cement finish area.
3. For me, all floor finishes must be at the same level to eliminate awkward transition strips or ramps between 2 different materials. Unless, design requires an area to have a lower FFL than the rest such as the shower area, utility rooom, etc. A good example are the hotels or condominium. Did you notice any transition strips between 2 different materials? Screeding or concrete topping or mortar or substrate usually accommodates the difference between the structural slab and the floor finishes. The structural slab usually is at the same level throughout except when required to have a drop in level due to drop in FFL or due to structural.design.
Overall, the purpose of this post was to find out if there's a "set-in-stone" rule or standard that architects should follow when it comes to "which goes 1st" when indicating your levels (FFL, SFL or SSL); and to know the different reasoning behind it.
Non Sequitur
Jan 16, 20 8:20 am
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.
OddArchitect
Jan 16, 20 9:51 am
creams to me?
Non Sequitur
Jan 16, 20 9:54 am
^Ha...
Jen_C
Jan 16, 20 10:10 am
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.
SneakyPete
Jan 16, 20 11:51 am
Non Sequitor also steals all of the contractors calculators before they start.
Non Sequitur
Jan 16, 20 12:04 pm
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.
SneakyPete
Jan 16, 20 12:53 pm
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?
Non Sequitur
Jan 16, 20 12:56 pm
^Hey now... don't take away our fun
Jen_C
Jan 16, 20 1:51 pm
@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.
Non Sequitur
Jan 16, 20 2:19 pm
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.
Donna Sink
Jan 16, 20 2:29 pm
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.
OddArchitect
Jan 16, 20 2:48 pm
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.
Non Sequitur
Jan 16, 20 2:54 pm
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.
OddArchitect
Jan 16, 20 4:35 pm
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-)
Jen_C
Jan 16, 20 10:43 pm
@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.
Jen_C
Jan 16, 20 10:56 pm
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.
Jen_C
Jan 16, 20 11:06 pm
@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.
Miles Jaffe
Jan 16, 20 9:59 am
Once again, tduds for the win.
OddArchitect
Jan 16, 20 10:09 am
This has been an interesting thread. The few firms I've been with it's always been FF at 100'-0" and it referenced TOS.
tduds
Jan 16, 20 12:32 pm
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.
OddArchitect
Jan 16, 20 12:45 pm
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"
SneakyPete
Jan 16, 20 12:52 pm
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.
OddArchitect
Jan 16, 20 1:25 pm
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.
Jen_C
Jan 16, 20 10:09 am
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.
Miles Jaffe
Jan 16, 20 8:54 pm
Just to add a little seasoning: dimension RO or center of opening?
Jen_C
Jan 16, 20 11:10 pm
RO for me. While I get it why some uses the Opening CL.
OddArchitect
Jan 17, 20 9:27 am
RO for me too. We don't to much residential work.
Donna Sink
Jan 17, 20 10:22 am
Center.
OddArchitect
Jan 17, 20 10:31 am
Donna, do you do a lot of wood framed construction?
Almosthip
Jul 22, 21 4:37 pm
Center of opening in wood framing, R/O for openings in masonry
peijunfei
Jan 16, 20 10:42 pm
Idk why so many F to confuse ppl, if is not too complicated project, I just do:
FFL/T.O.F.F:finish floor level, top of finish floor
T.O.SLAB: self-explanatory
T.O.STEEL/B.O.DECK etc to describe structure.
and B.O.CEILING and so on...If still confusing, check the AIA handbook, I remember there is a cad drat standard something. Remember the drawing's purpose is to clarify not to confuse ppl. They will be handed to client, contractor to read and bid and build.
mohandsalah
Jul 22, 21 1:19 am
Starting with the approved FFL as it depends on many factors, then based on finish layers the structural slab level is determined SSL. When an architect starts new design he will set the FFL based on his space calculations for each floor and accordingly calculate the SSL as he already specified floor finishing materials and thicknesses. Usually our reference during construction phase is SSL based on an approved shop drawings, The Base reference for all disciplines will always be Finish Floor Level FFL. :)
Hi,
I need your opinion on this item. I had a conversation today with colleagues about which Floor Level is the basis in determining the other Levels in a storey. Is it the Finish floor level (FFL) or the Structural Finish Level (SFL) or the Structural Slab Level (SSL)? Correct me if Iam wrong, FFL refers to the level at the top surface of floor finish. This is where all the building element finish levels are referenced from. SFL refers to the level at the top surface of the floor screeding or concrete topping. While SSL refers to the level at the top surface of the structural slab.
Now, when an architect starts to design a storey, which one do you use as your Floor Level? Is it the FFL, SFL or SSL? Also, whichFloor Level serves as the basis of setting the other levels in a storey? Is it SSL is given first then you figure out the SFL then the FFL or the other way around, FFL is set first then the SFL then the SSL?
What are your thoughts on this one? Thanks in advance for sharing.
FFL
Are you asking what is 100'-0" or 0'-0"?
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?
I’m assuming here that FFL includes the thickness of ceramic tile or whatever floor covering. We don’t bother with this and use a top of slab or under side of deck dimension.
This sounds more like a revit level set up question that a CA one.
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.)
We use 100'-0" as top of main floor slab.
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 the way to go. FFL is always bound to change and is dependent on too many variables.
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.
Are you the architect or the structural engineer?
Do you need the fixed level to be the surface that's walked on or the structure that holds it up?
Do you want the level in the model to provide the element least likely to move?
Do you want your contractor to need to do math?
Make a decision. There is not right or wrong. If your priority is FFL, use FFL. If your priority is making the contractor not have to think, use SSL.
My opinion is that we're architects. We care about the finished building. We also work with dozens of intelligent, capable humans who are responsible for their own various portions of the project and don't need crutches. Use finishes for dimensions and make damned sure your details, schedules, and assemblies are dimensionally correct and provide enough information to eliminate possible RFIs.
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.
In my experience, whatever we call out, the Contractor actually uses the top of slab as his reference, for everything from floor-to-floor heights to door heights. Based on this, I try to note the drawings clearly that way, and reserve any reference to "finish(ed) floor" for details where it actually matters - then make it very, very clear on the detail that I am pointing to the floor finish, not the slab.
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.
Thank you everyone for your comments. This conversation came about when I had a kick off meeting with our team lead. I wanted to find out how he wanted to show the Architect's intent in the drawings so everyone are on the same page. My role in the team was to help out with the production of drawings.
Anyways, this is why I posted this item here to see what is the industry standards here in Canada or US. As the Design Architect or technician, we should be able to communicate or translate the design to working drawings where it would show the clear intent of the design to the persons who are building it. Be it in Revit or CAD or manual drafting.
In past, I've always used FFL (top of the floor finish) as my point of reference to determine the SSL or the underside of joists. I do not even bother thinking about the SFL. This has been my practice and have seen some architects, GC, CM and PM do the same. This process may be different with wood constructon but, most of the time, it can be applied as well.
From my understanding, why FFL is always the point of reference in a storey is due to the following design reasons:
1. Architects mostly deals with the design. How the whole structure interior and exterior would look and function. Also, someone told me, Architects lead the consultant team, therefore, its always the Architect (responsible for the finishes) will dectate the reference based on the top of the any finishes.
2. All of the code requirements regarding minimum and maximum heights and clearnces are based on the finishes and not from the SSL ( Top of Slab) or SFL (Top of floor screeding or concerete topping). An example for this one are the handrails, guard rails, door heights, finished ceilung height and headroom clearances. If all minimum clear heights are reference from SFL or SSL, how would you comply to the minimum requirements when there's about a 25mm difference between the SSL and the FFL? How are your door panels going to look? Are the door panels going to have various heights due to different floor finish thicknesses while maintaining the industry standard gap requirement for doors? A ceiling height of 8' is not a true 8' at a granite floor finished area compared to the ceiling height at the exposed cement finish area.
3. For me, all floor finishes must be at the same level to eliminate awkward transition strips or ramps between 2 different materials. Unless, design requires an area to have a lower FFL than the rest such as the shower area, utility rooom, etc. A good example are the hotels or condominium. Did you notice any transition strips between 2 different materials? Screeding or concrete topping or mortar or substrate usually accommodates the difference between the structural slab and the floor finishes. The structural slab usually is at the same level throughout except when required to have a drop in level due to drop in FFL or due to structural.design.
Overall, the purpose of this post was to find out if there's a "set-in-stone" rule or standard that architects should follow when it comes to "which goes 1st" when indicating your levels (FFL, SFL or SSL); and to know the different reasoning behind it.
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.
Once again, tduds for the win.
This has been an interesting thread. The few firms I've been with it's always been FF at 100'-0" and it referenced TOS.
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.
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.
Just to add a little seasoning: dimension RO or center of opening?
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
Idk why so many F to confuse ppl, if is not too complicated project, I just do:
FFL/T.O.F.F:finish floor level, top of finish floor
T.O.SLAB: self-explanatory
T.O.STEEL/B.O.DECK etc to describe structure.
and B.O.CEILING and so on...If still confusing, check the AIA handbook, I remember there is a cad drat standard something. Remember the drawing's purpose is to clarify not to confuse ppl. They will be handed to client, contractor to read and bid and build.
Starting with the approved FFL as it depends on many factors, then based on finish layers the structural slab level is determined SSL.
When an architect starts new design he will set the FFL based on his space calculations for each floor and accordingly calculate the SSL as he already specified floor finishing materials and thicknesses.
Usually our reference during construction phase is SSL based on an approved shop drawings, The Base reference for all disciplines will always be Finish Floor Level FFL. :)