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Scale in Drawings

Learner101

I was always taught to make drawings to a specific scale as per the size the sheet. So when we send a drawing for construction, does the contractor carry a scale with him to read some of the dimension that are not mentioned in the drawing because i would not like to fill the drawing with dimensions everywhere.

 
Jul 16, 18 12:58 pm

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senjohnblutarsky

You should be putting dimensions on the drawings.  We have notes that specifically tell the contractor not to scale the drawings.  Scaling a drawing is imprecise. When you're getting down to fractions of an inch, on a 1/8" or 1/4" plan, there is no way they're going to get it right.  And those fractions of an inch can make a difference when it comes to ADA clearances, or clearances for some specified assembly.  

In short, if you want a contractor to know something, you better tell them.  If you don't, they're going to make it up, and you could be stuck with the results.

Jul 16, 18 1:08 pm
Rusty!

Ask your supervisor, not the internet. If you are the holder of primary design contract, then I kinda feel bad for the client. This is the kind of a question that should be asked by an intern to the project architect. 

Jul 16, 18 1:10 pm
Learner101

Thank you for you time 'Rusty'. And don't feel bad for the client as I am still studying, not in the field.

Rusty!

Drawings that you produce in school are not construction document level. They are schematic design and you may want to dimension certain things just to communicate basic spacial relationships. You don't need to dimension everything. Just relationship between more design critical components.

Non Sequitur

rules of construction documents:

  1. Do not scale drawings
  2. Do not scale drawings
  3. If in doubt, request clarification prior to commencing work
  4. whatever else you want

Drawings are drawn to a logical scale based on the information in that particular drawing.  For example, it is ridiculous to have jamb clearances or membrane lapping notes on a 1:200 floor plan... the poor guy working that part of the project likely needs a 1:10 or 1:5 detail for that.

You're responsible to dimension what is important to the design and indicate minimum clearances where critical.  Don't assume/expect the GC to guess the intent of the draftsman, it'll only end up costing your client more in extras.

Jul 16, 18 1:11 pm
thisisnotmyname

No.  Any dimensions you care about actually being correct need to be indicated on the sheet. The contractor may have an architect's scale somewhere in their office or in the job trailer, but the workers that actually build it will only have a tape measure at most.

So, inch, half, quarter, and eighth scales are best.   It's too hard to figure out 3/8 and 3/32 scale drawings with a tape.  

Jul 16, 18 1:12 pm
randomised

Write 'm down! No contractor is going to measure your drawing, they'll read your drawing. Also, what if you do everything to scale on let's say an A0 (not going to translate to American sizes) and they print it out in a handier size for on the job, A4/3 etc. Then what with your scale?

Jul 17, 18 3:44 am
Non Sequitur

"let's say an A0 (not going to translate to American sizes)" 

Love it. 

 Likewise, perhaps my post above passed over the OP's head.

Learner101

I'm pretty sure a posted a comment saying 'it is clear'. Also, thank you for your time.

Learner101

Thank You All. It's all clear now.

Jul 17, 18 4:45 am
Almosthip7

Very first note on every sheet in my set of drawings:

"DO NOT SCALE THIS DRAWING.  REFER TO GIVEN DIMENSIONS."

Jul 17, 18 10:44 am
SneakyPete

A bit over the top, no?

Pretty sure the OP's question has been answered at this point so I'll derail the thread slightly to ask about digital drawings and scaling dimensions. 

With tools in bluebeam (and I'm sure other programs) allowing you to set the scale of the drawing and snap to drawing points you can actually scale drawings pretty accurately. And that's only for digital versions of the drawings, what about using the BIM as a contract document, or even AR or VR for project delivery. At what point will dimensioned drawings become obsolete because all the contractor has to do is ask Siri or Google what length to build the wall? 

Of course, this all depends on the drafter/modeler being able to accurately draft/model things with the correct dimensions embedded, so anyone that has had to clean up other peoples' poorly drawn CAD or BIM probably knows that it isn't going to happen anytime soon ... amirite?

Jul 17, 18 1:55 pm
Non Sequitur

"this all depends on the drafter/modeler being able to accurately draft/model things with the correct dimensions embedded. "

 Most important point... garbage in, flaming garbage out. Everything we send to site is for information only... even BIM. I can't be bothered to spend an extra 3-4 weeks to make sure that all areas of the model are 100% accurate just in case the GC wants to cut a section across that 9th floor corner office (which is already called up as similar to the properly annotated on level 6). Should I also take time to model finishes and trims in case the GC does not read the finish legend?

Almosthip7

Digital drawings are living documents and are updated as the project progresses. Contract documents cannot be a living document. The lawyers would have a field day!

I'm not saying it's a good idea, I just hear people (who apparently know the direction of the profession) talk about this like it is the next big thing. Usually they have not been involved in producing a set of drawings or running CA on a project in the last 20 years.

Digital drawings don't have to be living documents, or if they are, they can be handled in a way that prevents them from being altered without authorization (I swear someone was talking about using blockchain for this recently).

Not to mention contract documents are already living. That's why there are contract modification procedures.

Rusty!

If you are facing contract modification procedures, then the architect dang goofed especially if GC is initiating them.

Contract modifications don't always come from the GC, and even if they do, it doesn't mean the architect goofed. The Owner can change their mind and want something different too. Or, shockingly, sometimes the AHJ just decides they want to see something different and won't give you the C of O unless you change whatever they think is wrong ... you've got to make that change somehow. Plus, the standard of care is not perfect documents so if the architect goofed (which will happen eventually) the contract documents need to be changed. If you think contract documents aren't already living, you're kidding yourself.

archanonymous

Now that question has been answered, I can derail the thread... How do USA people feel about weird scales? Like 3/16, 3/32, 3/64, etc?




As a young PA I usually have no issues with it, but only because the first thing on every drawing is "do not scale..."




As to tolerance, if there is an ada or other crucial clearance, I hope you've got 2" tolerance in it, in the USA at least...

Jul 17, 18 5:43 pm

What are you drawing at a scale smaller than 1/16 that isn't using an engineer's scale? And what are you drawing at a 3/16 scale that won't work at 1/8 or 1/4?

Non Sequitur

1:10 is where I get most of the important stuff done. 1:5 for membrane lapping as required. Don't know what those equal in imperial but we never use odd scales (like 1:75, 1:30, 1:125, or whatever the intern dreamed up this week). Just makes you look like you don't know what you're doing. Saw a drawing set from another office a few months back that all details were 1:7.5

SneakyPete

3/32 and 3/16 are on a standard scale rule. The are not exotic. I've personally (anecdotally) found that 3/32 is the best scale for overall floor plans.

senjohnblutarsky

I was involved in a project that went out with some 3/32 plans.  I wasn't a fan. 

In general, I stick to 1/16 (big buildings only), 1/8, 1/4, 1/2, 3/4, 1-1/2, 3, 6, with the occasional 3/8 and 1".

Jul 18, 18 7:50 am

3/16 is the bastard scale, and more than one contractor has underbid by scaling his takeoffs at 1/4".

And this is where scaling drawings is common - not in building (critical error), but in estimating.

Jul 18, 18 8:58 am
thisisnotmyname

We've seen similar bidder errors where 3/32" scale was mistook for 1/8".

alexbeebe

As a PM for a contractor, I have to say that I am a little offended that architects and engineers assume we don't use scale rulers. I don't think there is a single estimator or PM that doesn't carry a rule with them at all times. I agree that scaling becomes a problem when you print the document. Some people don't realize that the drawing was made with a certain sized paper to begin with. Print it out half size and your scale is off. 

         Word of advice for engineer's. Always include a scale legend on your scaled drawings. or at least one written dimension so that we can scale the drawing accordingly. This should eliminate risk of print size being different than the digital file and throwing off dimensions. Any good contractor will calibrate the scale with his scale rule before taking anything off, drawing anything for pre-fab, or building it in the field. 

       BTW, if you're field guys are using a scale rule to measure instead of working off of fabrication/construction drawings made by your own CAD department, then you really need to evaluate your process. Unless the project is small enough to not warrant it. In those instances your field crew will most likely field verify as they install to ensure real-world accuracy.

        Bluebeam is my tool of choice for takeoff purposes. You click two points, make sure that you enter the dimension the engineer gives on the scaled drawing, and the program calibrates the scale for you. If you hold shift when measuring, it produces a a straight line as long as you don't move your mouse past 45 degrees from center in any direction. little tip for anyone who wouldn't know that for some reason. 

          I agree that garbage in is garbage out. If you want a contractor to buiild something to a certain accuracy, make sure what your designing off of is accurate to the accuracy you want to see it at. I've seen jobs where existing beams and walls were shown on contract drawings as multiple feet from where they actually existed. Scanning tech is a great tool to create a walkable model of existing conditions. we use it all the time. Just make sure you align it with good control points on your backgrounds. 

           Just a couple of thoughts from one of us dumb contractors. 

Aug 14, 19 10:18 am
Featured Comment
Non Sequitur

General note no1: Do not scale drawings

General note no2: When in doubt, ask for clarification

If you measure and fail to follow-up (see note 2), any errors from that point on are yours to swallow. 

Yeah, its not that architects don't realize that contractors will scale the drawings, because we do ... its that architects don't want to be blamed when the scaled dimension is wrong. If the architect hasn't given enough information in the drawing without needing to scale something, the proper way to get that information is to ask for it.

To the contrary, we do assume that some numbskull will scale the drawings. We also assume that they will fuck something up by doing so. Those little numbers on the drawings are called dimensions. If something is missing or not clear look harder. If it is still not clear ask the architect.

Non Sequitur

Miles, let's not forget curcial step no.3: Wait for a response from the architect before building it

SneakyPete

Architects: Do Not Scale Drawings. Also Architects: Ships drawings without sufficient dimensions called out.

I don't usually find that there are that many missing dimensions on contract drawings. Sometimes the issue is that contractors are not looking at the entire set. Interior elevations rarely contain dimensions for wall length and height, but contractors may be looking at those drawings to do take offs for wall finishes. So rather than look at the plans and the RCPs to get wall length and height, they pull out the scale (or calibrate in bluebeam) and just measure what they see on the interior elevations.

SneakyPete

Sure, YOUR drawings... :)

lol, then get on top of that SneakyPete. It won't fix itself.

SneakyPete

Mine are as good as I can make them. I'm fairly certain that many of the reasons contractors whine about Architects are justified through experience, though.

b3tadine[sutures]

If I've heard once, I hear it bajillion times; "I used Bluebeam to scale your drawings." 

You know, nearly every set of drawings architects and structural engineers produce has in their general notes - DO NOT SCALE DRAWINGS - you do so, at your risk. Please with the "We don't have the time to send you an RFI." It's bunk. 

My drawings are for design intent, they are not perfect - and nowhere in the drawings is perfect implied - if a dimension is not included - DO NOT ASSUME - RFI. 

If a beam is in the incorrect location - DO NOT ASSUME WE SHOULD KNOW, BECAUSE MAYBE OUR OWNER IS A CHEAP FUCK and WILL NOT PAY FOR A MILLION HOURS VERIFYING EXISTING CONDITIONS - point being, you don't know ALLLL what came before you - send an RFI.

Oh, and read all of the drawings, not just the structural, the entire set. Understand how the building sequences, and goes together.


tintt

Clients don't want to pay for contractors to send RFI's or sit around reading and coordinating drawings either. That's why we call it race to the bottom.

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