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Metric Dimension Suffix 'CD'


Bill Tillman

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This may be an easy one to answer. I'm working with a set of drawings from a detailer in London and the units is set to Centimeters. Okay, that's cool, but I notice that when they get to the landing on some elevations for stairs they change the FFL dimension to another unit of measure and they use a suffix of CD on the end of the dimension. It looks like they are converting it to feet, but the numbers don't calculate out accurately. Close but not accurately. Can someone enlighten me on this nomenclature?

 

And BTW, what's the deal with hatching everything with drawings from overseas. I'll admit it looks nice, but man does it ever make the drawing busy with what I consider way too much fluff.

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I'm not sure what FFL means. I would interpret CD to stand for Center Distance, but that doesn't explain the differing units unless the whole thing is out of scale and the dimension itself is overridden.

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FFL would be finished floor. I think some of our friends in jolly old England might be able to chime in on this after hours.

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This may be an easy one to answer. I'm working with a set of drawings from a detailer in London and the units is set to Centimeters. Okay, that's cool, but I notice that when they get to the landing on some elevations for stairs they change the FFL dimension to another unit of measure and they use a suffix of CD on the end of the dimension. It looks like they are converting it to feet, but the numbers don't calculate out accurately. Close but not accurately. Can someone enlighten me on this nomenclature?

 

And BTW, what's the deal with hatching everything with drawings from overseas. I'll admit it looks nice, but man does it ever make the drawing busy with what I consider way too much fluff.

 

My experience is that architects in the UK usually work in millimetres, so someone who is working in centimetres might have continental Europe leanings.

 

FFL stands for Final (or Finished) Floor Level. So it is a level rather than a dimension, although you could look at it being a vertical dimension from the zero datum. I have only seen the suffix CD in levels of harbour construction, meaning levels above Chart Datum.

 

Of course the context is all, and a picture would explain more perhaps.

 

You are lucky if it is only hatching. I usually have to deal with solid hatching.

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As the other have said FFL is usually Finished Floor Level.

Although, less often, it can sometimes be First Floor level. GFL, FFL, SFL, TFL - Ground, First, Second, Third. (Stops working properly when you get to Fourth & Fifth).

 

CD could be Construction Datum.

Sometimes a height datum for the whole site, sometimes a target point for laser surveying.

https://www.reference.com/business-finance/datum-point-construction-6fe05f75efd1160

https://www.berntsen.com/Construction/Smart-Targets-Datums-Reflectors/RS21-Datum-Marker

 

The 'odd' dimensions may be related to surveying equipment. Possibly ordinates rather than distances?

 

The only way to be absolutely sure is to email the originator of the drawings and ask what system / standards he has used.

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Construction Datum, that makes sense. And Eldon, yes these are solid hatches, some of them looking like painted wood. Honestly, I think this is such a big waste. It only make the drawing look good for the first few seconds of examination. When one starts trying to make revisions or pick out working points, it's like trying to open a box that's wrapped up in several layers of paper.

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