Process question for architectural users

I am doing some masters research on different approaches to block use, and I
would like to query the group.

I know 'traditionally' a generic size for windows is used, dimensioned to
the middle of the window, and if the installed window is an inch or two
different, the error is ignored, i.e. the drawings are wrong but acceptable.
However, I think this is similar to the 5" wall convention held over from
hand drafting days, and I am interested in hearing from people who have
chosen to at least question this held over convention, even if (especially
if ?) the experiment failed and you chose to go back to a nominal
convention.

So...
Do you have generic blocks, or do you have sizes based on actual
manufacturers sizes.
If the latter, do you decide on a manufacturer in SD, or do you size
generically early on and resize later based on the actual spec'd
manufacturer.
If using blocks, do you include the frame in the block?
If so, do you differentiate between windows, where the frame is 'inside' the
unit dimension, and doors where the frame is 'outside' the unit dimension?
Do you differentiate between the thicker frame common on windows and the
thinner frame common on doors.
Do you differentiate the frames between manufacturers (assuming you
differentiate blocks between manufacturers) or use a generic frame dimension
with manufacturer specific unit dimensions.
Do you differentiate graphically between different window types, i.e.
different graphics for casements and double hungs?

Also, any comments on the wall size issue? Is there a correlation between
drawing manufacturer specific windows and drawing dimensionally accurate
walls (be it 3.5" walls with no finish shown or 4.5" walls assuming 1/2"
gyp, or whatever)? Or are the two issues separate, and some people will use
manufacturer sized window blocks in nominal 5" walls, and vice versa?

Lastly, for anyone using ADT or Revit, do you feel that nominal/generic
dimensions make using the more 'advanced' tools easier, or harder? Does the
approach used in simple 2D AutoCAD drawings affect the ease of transition to
an Architecture specific 3D product?

Thanks for any comments,
Gordon

 

We use generic door and window sizes for most manufacturers (i.e., those who
manufacture to those sizes as "nominal"), and manufacurer-specific sizes if
and when we know for certain that the owner is committed to one of the
manufacturers (e.g., Andersen) who produce non-generic sized product.
However, most of the plans we produce are for builders, so we don't know up
front which window manufacturer they will source from. So, we most often
use generic sizes, dimension to centerlines, and have to trust them to make
the necessary adjustments if they choose a vendor that produces odd sizes.

We treat doors similarly.

We normally don't use blocks at all for most windows and doors, but rather a
semi-parametric insertion routine (AutoLISP) that generates correctly sized
units on the fly.

Walls are another matter. We draw exterior walls at 6" thick, intended to
include 2x6 nominal studs and the interior gyp board but not exterior
sheathing, siding or other finish materials. This allows exterior dimensions
for framing to correspond to outside dimensions for footings and foundations
(it's customary in these parts to set framing flush to the outer face of the
foundation stem wall).

Interior walls are usually 4 1/2" (2x4 studs plus 1/2" GWB on each side),
but may also be 4 5/8" or 4 3/4" where 5/8" GWB is used on one or both
sides. Add 2" for 2X6 stud walls. Dimensions, again, are to centerlines;
we've found that most contractors prefer this in the long run, since after
the first "face" is established "face to face" and "center to center"
interior dimensions will be the same; it's simpler than having to go back to
the drawing to determine which "face" is being used for each interior wall.

We don't use ADT or Revit.
___

 

Gordon,
Ditto Paul's answers on windows and doors.

But for all walls we draw net stud dimensions (i.e. 2x4 = 3-1/2" thick walls). We do that because the plans are primarily for the framers. They're the first ones on the job after foundations. And framers can't be relied on to correctly add or subtract the appropriate wall finish thickness. A wall might have 1/2", 5/8", two layers of 5/8" gyp.bd. - not to mention possible plywood shear panels, wall tile, etc.... It's pretty hard to hook a tape measure on a surface that's going to be there only in the future!

So we draw the walls, to face of stud, to the proper dimensions to achieve our desired net room dimension.

Gary

 

Similar to Paul on windows and doors. Our window blocks are drawn
consistently with door blocks in that the distance between "jamb" lines
represents the finished opening -- it's smaller than the nominal window size
to account for frame thickness.

Similar to Gary on walls, in that we dimension to studs exclusively, no
finishes. However, we draw stud walls at 4" or 6" thick. The reason being,
we don't put fractional dimensions on floor plans unless it's really, truly
necessary, which is exceedingly rare. So we draw the same way we're going to
dimension. Room dimensions are always nominal, with no concern for finishes.
If a room size of 12' is intended, we're going to dimension it 12'-4" from
center to center of nominal 4" walls. In no case would we dimension it as
12'-3 1/2" (or 12'-4 1/2" if we were going to account for drywall), so
there's no benefit to us in drawing the wall thickness "accurately."
Besides, it's faster to use the round numbers.

I've been around long enough and done enough different building types that I
think I've seen just about every possible type of dimensioning system. None
are perfect. Some are better suited to particular building types. I don't
think that CAD has really changed any of these issues significantly. It's
possible now to draw at higher supposed level of "accuracy," but if that
doesn't show up on the prints, it's meaningless to the builder.

Since windows are located to centerline anyway, for instance, I don't think
that it matters whether the graphic representation of the unit width is
perfectly "accurate," as long as it's within an inch or so of being correct.
As a designer, I'm not going to crowd a window against a wall or corner so
tightly that this is going to matter -- even if I knew which make of window
was being used!

For residential work, these are pretty much the same conventions I've seen
in my part of the country since long before computers.

 

I can only wish that Architectural designers would draw a wall @ 3 1/2" or 5
1/2" (or what ever the case may be). I work in a residential setting and we
design wall panels and roof trusses from the architectural drawings provided
by our customers. It may not seem like a big deal but when a wall is called
out as a 2x4 wall, for us, it means literally a 2x4 (or 3 1/2"). Nothing is
more frustrating than laying out a whole house and then realizing that we
are off by 1" in all directions (or at lease give me a centerline dimension
if you are going to add the gyp or if you are not going to draw the wall the
correct dimension). The same holds true for the trusses, if all you are
going to tell me it is a 2x6 wall at least tell me if you are dimensioning
to the face of stud or face of sheathing.

 

I can only wish that Architectural designers would draw a wall @ 3 1/2"

Sorry I was unclear, I thought this should have been obvious from previous
replies. We dimension to outside face of exterior studs, and don't ever
dimension wall thickness. The plans clearly state what is being dimensioned
and to where.

If you know the walls are 2x4's or 2x6's, and you know the exact location of
outside face of exterior walls, and centerline of interior walls, how can
you get "off by 1" in all directions?" I can't see where a not-to-scale wall
thickness would bother a truss designer, given those well-defined control
points.

I should also note that by policy my firm does not provide CAD files of our
house plans to contractors anyway. So if you were working on one of my
plans, you would be drawing it yourself, to your own satisfaction, based on
our hardcopy dimensions, so this would be a moot point. If you did somehow
get hold of our CAD file, hypothetically, I would answer as follows:

In my area of the country, panelized wall systems are basically unknown --
they're probably more rare than log homes, metal framing, or ICF systems. We
design for conventional, site-built, stick framing, because that's our
market, and we do it in the manner that we believe is most cost effective
for us and our customers (mostly builders). If your wall system is one that
requires every face of every wall to be drawn to perfect scale, then I'm
sorry, but I would regard that as "shop drawing" issue for you, and not
something that should necessarily reshape our methods of practice. The
people who adapt a house plan to logs, metal studs, ICF's, or any other
building system that wasn't intended by us, are going to have to modify the
drawings to suit their own needs. Even though your building system may be
composed of standard components like 2x4's, if its fabrication requires a
degree of drafting precision that has otherwise never been necessary for us,
then I'd view it as the same kind of shop drawing issue.

 

Tom,

Don't get me wrong, I am not accusing anyone of poor designing I am just
saying that in my line of work (wall panels) it would be much easier to me
if all the walls were drawn "to scale". The problem I encounter most is
exterior walls labeled "face of sheathing" when in fact the walls are drawn
@ 3-1/2" (that is where the 1" discrepancy comes from).

As far as the truss issue, if we do not know if it is face of stud or face
of sheathing then the truss could be made an inch too long or too short.

The reason we use our clients electronic drawings is that we need to pull
out dimensions that generally are not included in typical plan drawings.

I am sorry if I offended anyone, it was certainly not my intention.

 

I'm not offended, sorry if I sounded that way. I don't think you'd have a
problem working from our drawings, as the face of stud is identified, and
all of our walls are located dimensionally. The graphic representation might
not be to your preference, but I don't think it would result in inaccuracies
in your work.

 

I wish more people adopted your way of dimensioning!

Do you dimension to the face of interior walls or to the centerline?

 

Do you dimension to the face of interior walls or to the centerline?

We dimension to one face of interior walls, and make a rule never dimension
that wall to the other face. By staying on one face, this amounts to the
same as a center-to-center dimension, but it does introduce an inaccuracy.
Floor beams in the foundation plan are dimensioned to centerline, based on
the 4" wall thickness, therefore (assuming the house is built perfectly to
plan) they're 1/4" off center of the wall above. This doesn't matter to the
stick framing, but it might matter for your wall panels.

This is a longstanding convention here, which I'd personally like to change.
My preference would be to dimension interior walls to centerline, but I
haven't been able to win this debate yet. For our market, the present system
works.

If I had my way, I'd dimension an exterior 12' room as 12'-6" from outside
face of stud to centerline of interior wall (if it were a 2x4 exterior
wall), and an interior 12'-0" room as 12'-4" from centerline to centerline.
This is irrespective of whether the walls are drawn at 3 1/2" or 4".

The only reason for our present face-of-stud convention is to avoid a
dimensional glitch where an exterior wall continues to become an interior
wall. By keeping to the face, we're always dimensioning the same wall the
same way. If we dimensioned it to the face in one place, and to the
centerline elsewhere along the same wall, we'd have to introduce a 1 3/4"
dimension somewhere to keep everything in agreement, and this firm has an
extreme aversion to using 1/4" dimensions on floor plans.

As I said earlier, I don't think any dimensioning system I've ever seen is
perfect in all respects.

 

Ever tried to snap a chalk line representing the center of a wall and the
align the wall plate to it? It's loads of fun.

 

Ever tried to snap a chalk line representing the center of a wall and align
the wall plate to it? It's loads of fun. Dimensioning to the center of walls
impedes the framer.

 

Ever tried to snap a chalk line representing the center of a wall and the

No. You'd have to be sort of, uh, dumb to do that.

When I worked on a framing crew, before I went to architecture school, if I
was doing layout work I'd carry a short piece of the actual 2x4's we were
using, on which I had carefully scribed a centerline. This is what I used to
transfer a tickmark from the given dimension, adjusting by 1/2 stud or a
whole stud width, depending on how the plan was dimensioned.

The reason for doing this, rather than measuring 1 3/4" for a half wall
thickness, was the fact that there was a significant variation in stud size
from one lumber shipment to the next. Some were consistently almost 3 3/4"
while others were a smidgen under 3 1/2". A basic rule of carpentry being,
never measure when you can scribe.

Having worked with both face and centerline dimensions, I liked the latter
much better, simply because they're unambiguous. You don't have to
constantly reorient yourself to the plan to confirm which face of stud is
dimensioned. You can quickly place a tick at each centerline, then use the
stud-scrap gauge to place the chalkline on whichever side of the wall is
convenient.

Part of the layout guy's job, I was taught, is to plan where the wall is
going to be built and which way it's going to be raised, and place the
chalkline on the near side so it's visible as the wall goes up. Therefore,
the chalkline went on the side where I wanted it to be, not on the side
where the architect happened to draw it. There's no better than a 50% chance
that these would be the same.

The point of an architectural drawing is to convey the design intent, it's
not to give any specific workman the exact dimensions that he needs.
Everyone on the job is going to need to do some figuring of their own to
translate the plan information to suit their own needs. The idea that an
architect's dimensions can be used directly by the framer, if they're given
from face to face, is just not correct, in my experience. I've consistently
seen fewer errors when walls were dimensioned to centerline, and I've
personally seen it to be much easier to handle in the field.

 

Dimensioning to the center of walls impedes the framer.

See reply below. I would say that poor framer has other impediments which
aren't related to the plans.

 

In this situation, where neither block shows the frame, but does account for
it, do you just manually show the frame condition when ganging windows
together, or a windows to a door? My thought for including the window and
door frame, even as a somewhat generic item, is that i can just put two
window blocks side by side and that joined jamb condition is drawn. Or put a
2X6 block in between for a reinforced jamb. Thus far I have found it very
convenient, but I haven't used the approach long enough to be certain there
are no gotcha's lurking.

In that condition, my 'prefered' method has always been to locate the
exterior portion of the wall, then show which face of the interior wall
aligns with the interior face of the exterior wall. Usually because exterior
walls are 2X6 and interior are 2X4. This allows me to dimension to face of
stud on the exterior, which is the easiest way to build. It also allows me
to show that the alignment is what is important, not the dimension. I think
showing design intent with dimensions helps the framer understand what I am
trying to do with the design.

I agree that centerline of stud makes lots of sense, and when pushing
optimized framing, with studs on 2' centers and interior walls on a 2'
module, it is easier to layout and eliminates the extra stud or blocking.
But with framing on 16" centers, my understanding from talking to framers is
that it is easier to start at an outside face of a wall, and go over and
over to the same face of interior walls. I draw my walls at framing
dimensions so that, when I really need to dimension face of stud to opposite
face of stud across a room (a 5' bathroom for example) I don't end up with
errors. I will still find someplace to leave the dimension run open, so that
all dimensions are round inches.
Also, I have heard of framers who work with centerline dimensions a lot, and
who just make a jig for wall layout. A couple of pieces of 3.5" track,
nested in each other, with a notch centered in the web on each end, allows
for a telescoping rule. Lay it down and extend, align with the chaulk line,
and scibe a quick mark down either side. Another approach I have seen is to
notch the ends of a 4' piece of 1X4 and put a 2X4 strong-back/handle on it.
Lay it over the snapped layout line and use a framers crayon to mark both
sides of the wall. With a few nails drive just a little bit thru the 1X this
tool grabs the subfloor and doesn't move around, making it easy for 1 person
to do wall layout.
That said, I would love to work with a framer who is on the same page like
that, but I would never try to tell a framer how to do it. At least not till
we had a good working relationship
Of course that is all a bit off topic, probably better for the Fine
Homebuilding forums

Thanks for the info, all. My thesis thanks you.

Gordon

 

From TRJ: "Ever tried to snap a chalk line representing the center of a wall and align
the wall plate to it? It's loads of fun. Dimensioning to the center of walls
impedes the framer."

Are you kidding me?

A dimension should be from outside of sheeting to center of windows, doors or walls. Then from center to center until you reach the end of the wall. Then the final dimensions should add up. When I lay out a wall I ALWAYS make sure they do.

Why I do this: When I lay out a wall I hook my tape on the outside of the sheeting and mark the center of the wall then mark 1 3/4" on each side. IMO any good layout man can do this without much thought. Then both OUTSIDE lines are snapped and the wall is put between them. I could spend all day explaining why 2 lines are the way to go, or why I ALWAYS use red chalk, but why waste the time.

From Tom: "I've consistently
seen fewer errors when walls were dimensioned to centerline, and I've
personally seen it to be much easier to handle in the field"

I agree 100%

I will say there are many ways to do things, some better some worse. Sometimes it just doesn't matter. I have always stayed away from scribing like Tom has stated for one main reason. That being you cannot trust that every 2x4 will be exactly the same. Heck, overnight a stud can warp just enough to cause problems.

For the most part I don't disagree with Tom except, ALWAYS measure. As long as you can read a tape measure you will be better off than scribing.

 

I know builders who will say that second line is a waste of time. Place one
line, then use a builders crayon to mark the side of the line the wall goes
on. Kind of like marking a cut line, and which side is waste, rather than
two lines to put the saw blade between. And the wall is framed on the
'waste' side so when you silt it up you see the line till the last moment,
then it is bumped as needed to align correctly. Not that this is the only
way, or the best way, just the way some builders I know prefer to work.

As for dimensioning to center of windows, this works most of the time, but I
have had occation to dimension a design where a single window on one floor
was supposed to line up with the edge of a long group of ganged windows on
another floor. The single window and the first ganged window where
dimensioned from outside corner of building to nearest edge of window frame,
and the rest of the windows where shown with NO dimensions. The builder took
the ganged window count and calculated the R.O. based on the manufacturers
formula. We did sho an overall R.O., with a note to discuss with the
architect if the actual windows chosen resulted in an R.O. more than 2"
different from that shown.

Best,
Gordon