Not-to-scale drawings question 1

[archeng59]

I am the EOR on a project where the drawings I issued were plotted to 1/8" = 1'-0". The architect and other consultant's drawings were plotted at the appropriate scales. When the architect printed the stick set of drawings for the contractor and everyone's reference sets, all of the drawings were printed at a scale slightly less than 1/8" per foot. In fact, the horizontal scale is slightly off but the vertical scale is way off. The architect is panicked that CD's were issued and not to scale. He is considering re-issuing the stick sets. What are the ramifications if he does nothing? I've never encountered or heard of this before.

 

[haynewp]

I would expect field problems. Even if your drawings say that dimensions control over scaling, they will still scale the details and come up with problems.

 

[MiketheEngineer]

FIX IT ---

WAY too many drawings are released today with little or no dimensions - I guess we are supposed to rely on the scale.

While this may not affect you - here is what I get---

A PDF drawing that has been scanned and then faxed or copied or both. ALL change the scale!!!!!

At 1/8 scale - something that was 10' orginally scales out to 9' for me... BIG PROBLEMS!!

Good luck

 

[youngstructural]

You're getting spot-on advice. I would take it.

Just my 2c.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[tngolfer]

When we issue drawings, we don't even put a scale legend on them to try and avoid this.

While someone could figure out the scale by measuring a dimension, we say not to scale the drawings in our specs.

I agree with reissuing them and telling the architect to scan them to scale.

 

[MiketheEngineer]

BTW and as a followup - I have gotten more than one set of drawings where the architect forget to change the scale that was probably on his template.

For example - 1/4'' and 3/16'' aren't that far apart and it really screwed things up since we were just doing a plan take off.

 

[mrpid]

Although my company prefers to indicate the scale (I have suggested to them that we do not), I agree with TNGolfer. When I review documents I look at the dimensions and do not scale. All dimensions required to build the structure should be indicated somewhere. If it was mistakenly omitted, I would rather have a contractor submit an RFI as opposed to scale it off a dwg. I do think dwgs should be drawn to scale, but sometimes they are not and sometimes when revisions are needed it is much quicker and not uncommon to change a dimension rather than redraw it.

In school I was taught NEVER to write the scale(i.e 1/8"=1'-0")and ALWAYS use a Graphic Scale. This would remedy the scaling problems associated with scans,faxes,copies and half size prints. However, in my professional experiences I cannot recall having seen graphic scales used.

My thoughts for what they are worth.

 

[jike]

I thought the abreviation "NTS" means "not too sure" or is it "not to scale"?

We never had this problem in the non-computer age! Just goes to prove that you can make more mistakes much faster with the computer.

 

[cooperDBM]

This problem has long predated computers. As mrpid pointed out it could often be caused by a dimension changing without redrawing the view. This was more common before computers when it was far more difficult to redo a hand drawn, and especially inked, view. Photocopiers weren't usually accurate enough to maintain a scale.

I even saw a summer student years ago scale from a half-scale drawing (11"x17") without realizing it was reduced.

Graphic scales are a good idea though we rarely used them.

Not sure if you were kidding but NTS means "not to scale".

 

[archeng59]

Some of the architects that I work with use the graphic scale but not all. I rarely use one, but might reconsider after what just happened. I have a note in my general notes stating the drawings are not to be scaled and that the contractor accepts responsibility for using scaled dimensions. I suspect the problem was photocopied drawings that were somehow "fit" to the sheet size, but I'm not certain that is the problem. Thanks for the comments.

 

[mrpid]

Another comment regarding Half Size Plots: I do not know if it is specific to our printer/copier (your standard office 11x17 printer/copier) but if a full size document is 22x34 then you would expect a 11x17 to be exactly 1/2 size; however, our printer cannot print to the whole sheet therefore it comes out slightly less than half scale or if you print to scale it will trim some of the border/title block. There are ways to remedy this by varying/changing your border size but the scale discrepancy was commonly overlooked by people not aware of this problem.

Just something to consider.

 

[DRC1]

Standard copiers do reduce slightly, about 1%. I have heard this dates back to their inception when the government was concerned about counterfitting.

Although I agree scaled dimensions should never be used for constrution, They are almost neccessary for bidding. With today's tight time frames for preparing an estimate, we have skipped many jobs that did not have scaled drawings because there is no way to do the take off, check to be sure equipment will fit, etc. f we do bid the job, there is genrally a significant contingency or caveats because a lot of the quantities are not verified. So, although they should not be relied on to be prcise, the close approximation they provide is often neceesary.

 

[jike]

I was definitely kidding! This is an old joke that has been around for years. Sorry it was not obvious!

Another "not to scale" story happen to a project that we were having soil borings drilled on and someone put it in the copier and reduced the plan. The borings got drilled alot closer than we wanted and missed a pocket of organics.

 

[BigH]

In my view graphic scales are always a must - even if you show the scale numerically (some of our drawings say it is x=y at A1, a=b at A3 and m=n at A4 (A1, A3, A4 are the metric paper sizes). It should also be noted that graphic scales always take precidence over numerically noted scales.

 

[chichuck]

jike,

I'm sure you were kidding, but it made my morning! I give a star for that nugget.


regards,

chichuck

 

[frv]

BigH-

Maybe in Geotech this is fine.

In structural, however, you may have a situation where the same detail applies at several locations, with the size being the only thing that changes from one section cut to the other. It makes no sense to draw that detail 3 or 4 times. This is why some details are purposely left vague as to size and the reader is directed to the plan or to a schedule to determine the proper size for that particular cut.


Having said that, however, I draw most everything to scale because, as others have said, you will get someone who will tr to physically scale the drawings, despite your efforts to discourage it.

 

[PatBethea]

RE graphical scales.

We use them on our site plans and other similar civil type drawings, but even they aren't immune to skewing during reproduction - especially over a fax transmission.