Topic: How Precise is CAD?

[craigr]

If I draw a Rectangle at 0,0 & 400miles,400miles - then zoom way in at one of the corners, will it be accurate down to the 1/8" ??

craigr

[JCTER]

400 units isn't very much.

Sure it will be.

400 inches, 400 miles, 400 parsecs... doesn't matter what the unit is.  Autocad just believes it's 400 long.  It has no idea what units are... you tell it that when dimensioning, and as far as Autocad is concerned, it's just text anyways.

400 is 400 is 400.

[craigr]

So when zooming in on floor plans, one would think that walls should be 3-1/2" plus 3/8"(x2) drywall = 4-1/4" thick.

Right?

When people draw a house for example, do they consider all of this?

Then, when the house is built, do the (good) construction guys follow it THAT close?

[JCTER]

I don't bother worrying about the thickness of a wall.  Stuff changes too often for me to go back and revise my drawings based upon every little finish change, like gyp board thickness.

Why would you ever draw that minutia level of detail on a floor plan?  That wouldn't -ever- show up on paper.

I draw my walls 4" thick or 6" thick, even, depending on stud width.  3 1/2" stud (or 5 1/2") + 1/4" gyp on both sides... it's a rough thickness, but it's good enough.  No way I'm ever going to worry about drawing every little thing exactly perfect in Autocad.

As for construction actually matching it... hell no.  They'll do their best, but the nature of wood construction and the methods involved, added to the fact that they can't spend all day worrying about fixing that last little trailing 1/16" off the end of their wall... no.

Where's this question coming from?  What are you trying to get at?

[craigr]

Just how things work.

I often use floor plans from outside sources and need to know the overall bldg dimensions as well as room dimensions for Electronic signal ranges.

Sometimes those plans are not drawn to scale or the scale has been changed for some reason. So, I try to find a door or something that I can 'make a guess' at it's size, then scale the entire floor plan off of that.

Sometimes I get bit doing it this way and it can cost us money. The last time I got bit, it costs us 2k.

So, I am always trying to learn how things work, in and effort get more accurate with my 'guessing'.

Thanks for the replies,
craigr

[JCTER]

I have no idea why they would scale their floor plans :\  Should always draw full scale.

But anyways... the "important" things get drawn accurately.  Out to out of building (or out to out of concrete foundation, or steel line to steel line) gets drawn accurately.

[Birdy]

You mean the important "to me" things get drawn accurately.
Craigr, that's why you get bit. Because other people dont draw things accurately.... because it isn't important to them.

So you should charge your customers more money to cover yourself from other peoples carelessness.

[craigr]

That happens to be one of my faults, I expect things to be done right.

Some of my coworkers tease me, they call me 'anal' (obsessive), about getting things right.

I have a difficult time with 'that's good enough'.

Of course, this means that I spend more time on tasks, and as we all know, 'time is money'.

[JCTER]

How would it have been drawn on the board?  Would your floor plan worry about the difference between 3/32 gyp board and 1/4 gyp board?

I don't draw my trim to be 100% accurate on the sections, either.  I just draw a quick representation of generic trim.  Not my job to design/pick the floor trim or moldings out.  So it's not my job to draw it either.

[craigr]

How would it have been drawn on the board?   Would your floor plan worry about the difference between 3/32 gyp board and 1/4 gyp board?

Good Point.

[Birdy]

3/32" gwg?
are you serious? 

[Birdy]

on the board it would've been redrawn.
that's the point.  CAD is supposed to allow us to collaborate and share the design data.

[JCTER]

3/32" gwg?
are you serious? 

I was thinking font heights, apparently 

[JCTER]

on the board it would've been redrawn.
that's the point.  CAD is supposed to allow us to collaborate and share the design data.

If it's a 3D BIM model where the linework is regenerated when you update the wall family with a different construction assembly, then sure, but I'm not going to go through a whole building and change every partition wall's linework in a floor plan so that the thickness of the walls reflect the owner's last second decision to switch the gyp board thickness to save a few bucks.

That would incur a bucket load of costs, incur a change order, or swallowing a bunch of cost that unnecessary.  No one is going to be able to tell the difference when the drawings are printed on paper, anyways.  No one should be scaling the wall thickness to determine anything.

[Birdy]

If it's a 3D BIM model where the linework is regenerated when you update the wall family with a different construction assembly, then sure, but I'm not going to go through a whole building and change every partition wall's linework in a floor plan so that the thickness of the walls reflect the owner's last second decision to switch the gyp board thickness to save a few bucks.

Whose job is it to change that stuff, regardless of how "last minute" it is?  If the drawing isnt changed, or spec noted, now all my door jambs are the wrong size!

That would incur a bucket load of costs, incur a change order, or swallowing a bunch of cost that unnecessary.  No one is going to be able to tell the difference when the drawings are printed on paper, anyways.  No one should be scaling the wall thickness to determine anything.

We are talking about electronic CAD files, not printed drawings.

edit:  if you know the stud is 5 1/2" why on earth would you draw it anything else?