AEC

Updated: Standard Text Height in Construction Drawings Should Remain 3/32”

11 Apr, 2005

Cadalyst Newsline readers respond to query about new standard


In the April 4 edition of Cadalyst Newsline e-mail newsletter (click here for archives or to subscribe), reader Timothy C. Doyle asked for feedback on industry standards for text height in construction documents, saying his officemates were questioning the need to maintain the 3/32" standard.

Newsline received a total of 21 replies initially from the field, and the consensus is that 3/32" should remain the standard. Then we received additional e-mail the following week with feedback from seven more readers.

Read on to peruse the 21 initial replies (mostly unedited), preceded by the seven, more recent replies, including those that offer exceptions to the rule.

Thank you to all readers who took the time to share their perspectives.

Replies for the week of April 4-10, 2005:

From David L. Johnson: Concerning the text height issue, I think it makes more sense to use 0.1 for a text height. It is easier to figure out what the proper text height should be. I would rather use a multiple of 0.1 than 0.09375. Example: What is 64 multiplied by 0.09375? What is 64 multiplied by 0.1? Which one can you do easily in your head? I agree that 1/16 is too small, especially for half size prints. Besides, you have to use a multiple of 0.0625. It doesn't make sense to keep things more difficult than they need to be just because that is what they did in the past.

From Mike Casey: We use 3/32" as a standard but I struggle with reducing from E size to B size which we do on P&ID drawings.  The text plotted off on a HP Office Jet gets a little thick.  I have experimented with the line weight and find that the text quality improves if I set the line weight to about half the default either .005" or .13mm. 

From Arthur Talbot: Am I the only one that noticed that 3/32" (.09375) is smaller than 1/8" (.125)?

 
From Charles A. Graham, Jr.: None of the respondents listed in the subject article mentioned the National CAD Standards. It is my understanding that all federal agencies require compliance with these standards. The standards do not dictate any size of text, but the minimum size for CAD drawings is 3/32", or 2.4mm. Oddly, the standard mentions hand lettering, with minimum text size of 1/8", or 3.2mm.
 
Some of the respondents discussed reducing 30"x42" drawings down to 11"x17" or smaller as a reason to go to larger text size. We have found that not only is 3/32" text not readable at that small a reduction, but none of the graphics are worth reading, either. For example, a masonry wall with one wythe of 8" CMU and one wythe of 4" brick appears at about 1/8" wide on large format drawings at 1/8" scale. Reduce that drawing to 11 x 17 and that 1/8" width goes to just over 1/20", or just a fuzzy muddle of a line.
 

From Joseph J. Denegre: It's great to see the resounding agreement on 3/32" text size, but NOBODY thought to address the issue of all caps versus lower case. As anyone with an interest in typography or book design can tell you, lower case text is easier to understand; that's why books are written in it. Caps is a holdover from hand and Leroy lettering. Ironically, we use one of those pseudo-handlettered fonts; but it looks great and reads well. And yes, we use 3/32" text height.

 

From Martin Streat: The discussion about font sizes prompted two answers from me. If when
plotting in paper space as we all do, the font size should follow the paper
size automatically. So a setting of 4 will remain constant whatever paper
size used. I'm sure the programmers could fix that?


My next answer is more of a question: Why are you funny old folks still
using inches? How can it possibly be right — look at your hands, the magic
ten everywhere! I am from the U.K., so i know all about inches, but we gave up
building in it years ago. Get a metric-only tape and move into the real
world.

From Ian A. White: Really, this question should never have been asked in the first place. Minimum text height standards form part of every country's national technical drawing standard. The fact that a drawing is done using CAD software does not change anything. It is like saying that because draughtsmen started using technical pens instead of pencils that all existing standards no longer apply. CAD is simply a tool.

 

Just another point. National CAD standards are those prepared by a national body comprising technical experts and members of the various associations and bodies covering a particular field and not a company that sets itself up with a name that implies it is a national body.

 

The Australia/New Zealand standard for Technical Drawing (AS 1100) covers this (as one would expect) with the minimum text height for drawings on printed sheets A1 (ANSI D) and smaller to be 2.5 mm (3/32"), with drawings printed on larger sheets 3.5 mm (1/8"). In no case should the reproduced height of text be smaller than 1.8 mm (3/64") when a reduced size print is made.

 

Sadly the fact that this question is asked shows that many drawing offices do not even have the most basic standards library. I commenced my engineering studies in 1972, and one of the required texts for every engineering student was a copy of the then Australian Standard for Technical Drawing - AS CZ1. I still have my copy, and I still refer to it as it covers areas not considered important by the current standard. Unfortunately such requirements are no longer mandatory, and many teaching technical drawing have never heard of their national standards.


Initial Replies:

From Mitch Mermel: Small text is great if you only produce full-size drawings. With the ability to reproduce drawings in different sizes, many of our designers and clients request half-size plots for coordination and check sets. 1/8" text in a full-size drawing obviously becomes only 1/16" high in a half-size copy. Reduce 3/32" text and it is still legible. Reduce 1/16" text, and you need a magnifying glass. If you need to put so much text in your drawing area it might be better to use a keynote callout, putting the note itself off to the side.

From William Shaible: I have been using AutoCAD to prepare constructions drawings and documents for the past 10 years. From the beginning, I have used 3/32" as a standard height for all dimensions and call-outs as opposed to 1/8". It makes for a cleaner presentation, and allows for more information to be placed in smaller spaces. Where drawings are very busy and space really becomes and issue, the text is sometimes "squeezed" by changing the width factor to 0.75".

From Todd Ockaskis: Our office a few years ago came to the same realization that smaller text allows more text on the drawing and also allows more "white area" between notes. You loose a little readability by reducing the size of the text but gain readability by the increased space between notes. To get everyone to use the same size text height we have modified the text commands with LISP to multiply the text height by the current dimension style. Therefore the user does not need to consult a table every time they change dimension styles.

From John Kemper: When I started as an intern architect in 1984 we were taught to make all lettering 5/32 of an inch tall.

A small bit of history as to why lettering was 5/32 of an inch:

1. Printers used to use the blue line reproduction for making of copies. This process tended to fuzz the drawings as the light was transmitted through a sheet. Printing a half size set used to be a 2 step process 1. reduce the drawings (introducing fuzz) 2. reproduce the drawings using blue line (introducing additional fuzz).

2. Most lettering was hand done. Each person had a different lettering style and some style reproduced better than others, even at full size. When drawings were reduced to half size hand lettering could be difficult to read. The taller the original text the easier and more likely that the lettering would be reproduced by the old blue line copy system.

When CADD started taking off we reduced the lettering to 1/8" as a half size computer text was consistent from user to user and the text was still readable at half size.

Print houses are much more sophisticated today. Prints are made on Oce Kip or Xerox large format copy machines and the copies are made directly from plot files or some sort of digital source. The copy and/or reduction process does not introduce the fuzzing that the blue line systems had.

However one thing to remember, we did the 5/32" lettering because Federal Government required all lettering on their projects to be at that size. Much of our work was federal government based so the office standard was 5/32 of an inch.

Does it make sense to continue to use 5/32? Probably not.

But as architects we are in a service industry. If the client has a requirement then we must comply. From Peter Tennent: In my previous job where we used A1 plots we used a standard text height of 3mm for the majority of text. In my current job we mainly print on A3 paper to make plans easier to handle and have settled on a standard height of 2.5mm. These tie in pretty close to the 1/8" and 3/32" that was discussed in your Newsline.

From Coral C. King: More and more clients are using half-size prints of construction documents. We have found that 3/32" text is the smallest which is readable at half-size printing. 3/32" is our standard and has been for more than 10 years.

From John Jarvis: As our firm transitioned from manual drafting to CAD in the early nineties, we established standard text styles that were based on Leroy lettering templates. Today, the text heights we use in construction drawings are somewhat dependent on the type of construction drawing, ie site development, utilities such as water and sanitary sewer, etc. Our CAD standards specify plotted text heights for proposed information to be at minimum .08 inches (site) and at maximum .125 inches (utilities). And yes, while the smaller text does allow for more information to be presented, this range of text heights is also legible on half-size plots which we see being used on an increasing basis.

From David Lark: Some years ago while developing standards I settled on 1/12 of an inch (.0833", 2.117mm) as the optimal text size. This is 67% of 1/8" and 89% of 3/32", and can be printed using bolder hand fonts and remain quite legible. Smaller text such as 1/16" (.0625") required use of thinner stick fonts. Remember that this shrinks text in both length and width, so you can squeeze 2.25 times the text into a given area at 1/12" than you can at 1/8". Also, the scale factors work out in round numbers, i.e. for 1/4" plans model space text is 4" tall, at 1/8" it's 8", etc.

A very professional architect who should know these things once asserted that 1/8" was a legal minimum for construction drawings. This sounds unreasonable; perhaps this applies to hand drafting. I believe the minimum font size for legal documents is 7 point (.0972"). These limits don't seem to prevent plotting with the width factor at .1, or in a myopia-inducing greyscale.

I've emailed my lawyer asking for clarification of the above points. Will get back to you when she has time to get to this. [Editor?s note: When we hear from David, we?ll update this file, so please check back.]

Speaking of lawyers, a glance at the yellow pages will reveal that attorneys always come after architects, and they outnumber us by at least 10:1

From Mark Martinez: Our company uses 0.075 high Arial text and B-size prints. Perfectly readable and allows for more information on a such a small sheet. I would be inclined to use a larger font if we used D-size prints.

From James Hutchinson: Being from the Great Southern Land (Australia) we have been fortunate to do away with that strange imperial 1/8" or 3/32" system. Our standard text heights are 2.5mm, 3.5mm and 5mm for main headings. The use of 2.5mm & 3.5mm are very often client driven. These days a lot of drawings are produced in A1 format, but are printed as A3 for use on site, so 3.5mm is used for ease of reading. What a joy it would have been, if long long ago, everyone had conformed to the same command aliases, same pen sizes for colours and the same layering convention. It is nightmare when you change places of employment, and everything different!

From Timothy Fierle: Regarding 3/32" text height standard for Construction Drawings: It is increasingly common to produce a 1/2 size drawing set for the owner and for site visits by the designers to hand carry. When necessary, the full size set is available in the construction trailer. 3/32" is barely legible at 1/2 size or when printing from 24x36 to 11x17. Any smaller text height will render these convenient 1/2 size drawings illegible. 1/8" text height is preferred.

From Michael A. Gilroy: For the last 25 years, 3/32" text height has been the preferred by every architectural office I've worked with. In all the "drawing standards" developed, it always came down to 3/32" text was more compact and reduced the visual clutter of the drawings. A side-effect was tighter sheets that fit on the next size down paper size. This was welcomed in the field.

From Darrell Mingo: As a draftsman with 20 years plus experience both at the board and on the job site, you may want to consider the condition that the drawings degrade to on the job site. They frequently have dirt, grease, paint, coffee, etc. inadverently spilled on them and can become very hard to read very quickly. The smaller the text size, the more information that can be lost under a stain.

From Brad Hofman: We have established .10" as our minimum text size for civil engineering construction plans (base our dimensions and notation on decimal inches/feet). Most of our field people work with 11x17 half-size plans and .05" is still readable. Also, we continually struggle against too much information on a given plan sheet, which leads to poor readability and expensive misreads.

From John K. Sehl: Virginia State Library Standards dictate a minimum letter size of 1/10" for any document to be recorded in Land Records.

From Glen Sullivan: The 1/8" text height standard is a hold over from the days of hand drafting. It is hard to clearly letter by hand anything smaller then 1/8". Plus, most people really wrote slightly small by staying within the 1/8" guidelines. With CAD, 1/8" text can look large because of its exactness of size and precise lettering. I have always preferred the small 3/32" standard, plus you can place more text in the same area. The only thing is that the font selected for this size should be a simple single stroke lettering style that is very clear to read.

From Simon White: Changing text heights? We go through this whenever we get an old designer, or one who is farsighted. Most of our drawings and blocks are based on standards: we use 2.5mm text, but our borders are all D size and are typically printed as B size, depending on the plotter, title block design. etc., which gives us a text height of about 1.5mm, slightly larger for 3mm text which we use for larger labels.

Every so often someone suggests that we should go over to 4mm text to make life easier. Sadly this would require us to redraw all of our blocks, redesign the title block, update all of our programming, and redo all of our standard drawings to accommodate the bigger text and to allow for there being room for less on a drawing.

In layman's terms: "Are you crazy?" We used large text when it was hand-lettered, and as we switched to CAD we started printing everything smaller but using the same text size. Because CAD text is more legible than hand printing in the smaller sizes (although arguably less attractive) this worked perfectly. Our text is about the same size as the text in most books.

We sometimes make an exception for checkers, usually the grizzled old guys with bad eyes after a lifetime of staring at drawings, and print things out C size or bigger, but changing our standards, prototypes, blocks and software after fifteen years of development? Unless you have time on your hands, drawings which are half empty, standards which need to be revisited and clients and staff with poor eyesight, I wouldn't recommend it.

From Steve L. Knight: When we established our text height standard at 3/32" years ago, it was based on the standard typewriter letter size. We decided this was a good average. Anything smaller would be harder to read by those with aging eyes. Also, when the drawings are issued as blueprints to the field, and the sun and rain has hit them, the larger text has a better chance of still being read.

From Ron Sprague: VERY DUMB IDEA. Having the text at a minimum of 0.11", or 0.125" is the minimum height to allow for reduced size printing and still be legible on the copies. At 0.11", the text on a 36 x 24 sheet can still be read when the sheet is plotted on an 8 1/2 x 11 sheet. If you go smaller, the text is not legible. There is an IEEE graphic standard covering this issue among other things that was published in the late 80's, early 90's.

From Hugh Thomson: Prior to the widespread use of Cad systems - the text standard for hand draughting was 3.5mm, approx 1/8". Microfiche archiving of drawings was common practice then and the 3.5mm handwritten text height ensured that clarity was still retained when the drawing was compressed to the size of the microfilm used.

There are some practical reasons for this too - the end product now as it was then is still a paper copy - printed at 1:1 scale the handwritten text at 3.5mm was clear and legible. With the introduction of Cad the text height was reduced to 2.5mm (app 3/32") - which given the extra clarity of a computer print out, ensured that the information was still legible, even when A1 size drawings are printed at A3. Also the end user is still the manufacturer or installer/builder, drawings get messed up with dirt and fingerprints - so it is very easy to obscure the text information on the drawing.

So in order to satisfy all criteria from design through to final build the drawing has many purposes and the text height of 2.5mm satisfies these criteria for cad generated drawings. From my experience anything less than 2.5mm can cause problems with clarity of presentation and usage.

I would standardise on the 2.5mm text height.

From Gordon Wittenberg: The current standard we use is 3/32" (2.38mm). For the amount of information that is required on many layout drawings, 1/8" (3.175mm) is just a bit too big, using 3/32" we can fit much more information on a drawing. I have experimented with smaller text but since we typically plot all drawings (for information purposes) to B size(11"x17"), 3/32" is about the lowest limit I would go to. I find that plotting Process P&IDs that are originally drawn on E (A0) size drawings to standard B size (11"x17") paper on a laserjet results in good legibility of the 3/32" text. However, some of us older guys do need a little help with bifocals at times but because all plant personnel have access to the original CAD files via a drawing viewer, this is not an issue.


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