Tuesday, March 3, 2015

Kit of Parts

Architects assemble buildings from individual parts in Revit. Pre-set elements are part of a templates and libraries for easy access. Any building starts from a kit of parts, just like the furniture from IKEA. A ready library of walls, floors, roofs, windows, doors, stairs, components, annotations, and formats can be customized to whatever you want for the design and documentation of architecture in the Revit Building Information Model environment. You can set it up as you please.


Is there a best way to approach to creating a uniform set of building blocks in Revit? Standards sometimes exist for standards’ sake and are not worth having unless they make things better. A good Revit standard keeps work clean and understandable, with fewer unnecessary steps or distracting choices; no need to “reinvent the wheel” every time. On the other hand, over-defined standards can become overwhelming, reducing speed and flexibility. The value of setting elements up before hand goes away if the Revit user is tempted to abandon the system and make what they need ad-hoc.

Building the Library from Generic to Realistic

A kit of parts that works in Revit starts with generic components and extends to the more complex. No need to force detailed decisions early. Provide a basic spectrum of choices systematically named so the designer can find them. Show only to the level of detail that is needed to communicate clearly, which is no different that in the days of hand drafting. Just because we can show high level of detail in Revit doesn't mean we should. Don’t weigh the process down.

Look it Up

One of the most important aspects of a good library is to clearly codify the choices. A graduated series of standard components can be given short, logical, findable names. Keep the library small, containing just the parts that serve as “seeds” for duplicating to similar types parametricly.
Human memory is limited, but we can always look it up, or make it as we need it according to a system.  
Standards should extend to the text, tagging and formatting of the model in all phases, from schematic through construction documents. Good standards streamline and help us visualize and communicate the work, The same model serves as the basis for clear diagrams and stunning presentations as well as highly technical documentation, with format styles already built in. In Revit, it is best to set it all up right from the start, with an effective kit of parts.

Wednesday, February 11, 2015

The Justification for Alignment

Architects love to align things,... professionally.   Original typesetting involved “justifing” text to “make it perfect” by aligning left and right margins, now anything that can be aligned uses this sense of the word.  Architects take a keen interest in this subject and Revit parametric models make it easy.  A prime example is how architects work with walls.  We assign a plane of alignment to a Revit object that helps quickly, precisely control how they are placed as we compose in plan.  (See the previous post, Dimensions - the Nominal,  the Actual, and the Usable,  for a “prequel” on Revit dimensioning).

Exterior Face, Interior Face, or Centerline

A building, unlike justified letter type, is in three dimensions.  Walls in Revit have a defined, flexibly 

placed justification plane, or “location line”. The easiest way to establish and use this is in a “flat” view - a plan, elevation, or section.  The location line refers to some aspect of the exterior face, interior face, or centerline.  In a typical case, the exterior wall location line is set to finished exterior face, say the  face of a brick masonry faced wall; The justification for a gyp board stud wall partition is frequently set to face of the supporting stud. the “core” of the wall.  In early planning, justifying to the centerline may prove easiest to control, allowing rapid experimentation and adjustment as spaces and rooms divisions are made in resolving program and room configuration.

Eyeballing vs. Nailing It in Schematic Design

Portion of a Schematic Design Plan View for a School
Defining that much may seem over-precise. Why not just “eyeball” (visually estimate the measure) the geometry loosely, at least in the beginning?. But nailing spacing to a precise dimension early actually helps keep design efficient from beginning to end in Revit.  At first, materials may not be easy to define and dimensions not known.  That doesn’t matter; use a placeholder.  A generic 12” or 16” exterior wall works to start.  A Generic 5” interior partition will do the job as ideas are forming, and can be swapped out later. Eventually, it may be 4 ⅞” or 5 ¼” , 7 ⅝”, or any of a number of other possibilities.  That level of detail can safely come later.  The designer can lay strings of working parametric dimensions to quickly adjust and control spacing, keeping geometry simple and understandable with walls alignment to a consistent location line.  Wall widths can flex as refinements are made without changing the basic dimension system.  Controlled adjustments can be made by simply “nudging” walls with the cursor, or changing the “live” working dimensions.  Room area tags can give feedback on resulting areas until a target is reached.  The model can be both precise and flexible.

Portion of a Construction Drawing Plan View for a School
Declaring Peace in the Dimensional War
Depending on your priorities as a designer or planner, the most important surface in a room will either be to the face of the underlying structure or to the face of the finish that is applied to it.  Architects seem to take sides on this when it comes to dimensioning methods.  The first thing placed in construction is the structure, in the case of a partition, the stud.  Place it to finish, and you force the framer to do the math on the fly as they subtract intended finish dimension to determine where to mark for the stud location.  Easy to make mistakes.  On the other hand, when detailing the precise placement of elements in a room, such as a counter or an opening, the designer wants to track the final appearance and fit, not the underlying structure.  Thus, the primary dimensions should be to the finish face, instead, right?  Revit’s versatility makes this conflict mute. The dimension can be placed to core, while the wall graphic still displays the actual dimensional position of the face layer.  The model scales in the true clear dimension to assure design fit while plan dimensions are to the core, the way it is constructed.  Design and documentation geometry can finally work together. Different plan and detail views can be created of the same model to meet the needs of the various team players.   

Perspective View of School Corridor Design
Revit enables collaboration and integration.  No need for the thinking of schematic design, interior design, and construction documentation thinking to stay isolated in silos.  One of the most important outcomes of using a model interactively like this is to allow us to form and describe the architecture with an eye to the final outcome, coherent and useful space.  A peaceful outcome.

Sunday, January 4, 2015

Dimensions - the Nominal, the Actual, and the Useable

“Order is the balanced adjustment of the details of the work separately, and, as to the whole, the arrangement of the proportion with the view to the symmetrical result.  This is made of the Dimension, which in Greek, is called posotes.  Now Dimensions is the taking of modules from the parts of the work: the suitable effect of the whole work arising from several subdivisions of the parts.” - Vitruvius, 1st century BC.

Dimensions are at the heart of Architecture, running through from initial conception to final detailed completion.  They are an essential system that runs through design thinking.  Architects are obsessed with them, and there is no end in the debate on how they are best used. Revit, a tool for parametric modeling, offers interesting ways for Architects to resolve dimensions in design.  But the tool is only as good as the thinking behind it.

Nominal vs. Actual

Shorthand for measurements abound in and around buildings: 2x4 stud, 8 inch brick, 8 foot ceiling, 10’ x 12’ room,  20 foot span. , These are not exacting, but offer a nominal size that we can easily get our minds around.  The cross section of a wood 2x4 rough cut board is actually 1 ½” x 3 ½” , plus or minus ⅛” (at least in my part of the world).  The 2” and 4” are nominal dimensions.   Architects obsess over dimensions in different ways.  In early  design, arguably,  nominal dimensions provide simplicity for the big picture, but certainly introduce problems.  Some special cases for rounding can be made, for example an indication of a room size to a client early in design, could be to the inch, or even the foot. 
I have reluctantly defined these special, grossly rounded dimension styles at times.  In a recent project, I found found them used in place of exacting dimensions. After that, I thought of banning rounding, but instead defined the style to shout out in a loud color limit their use and eventually flush them out. Nominal dimensions in a design fool us into sweeping issues under the carpet that will be faced again in the design of a building.  Critical dimensions must be precise: An elevator may not fit in the shaft required.  A corridor may too narrow to serve as an emergency egress. Trades may not be able to coordinate any number of construction tasks, given vague dimensions. But these vague, nominal dimensions may be useful to unclutter thinking in earlier stages of design….or are they?

Actual dimensions, accepting small fractions of an inch, can get complicated fast, but are the only option in the end for real construction tolerances.  Competing office cultures frequently war over this false dilemma - nominal or actual.  In Revit, dimensions serve to report for the size of the object to the to the foot, the inch, the 1/8th inch and even nearest 1/256th of an inch (a seldom, if ever, needed level of accuracy.  These “styles” of dimensions can be set to different parameters, but can report dimensions to unrealistic accuracy, just as reporting nominally, leads to problems.  Accuracy should not be confused with precision, which both early schematic and later detail design thinking alike can benefit from.

Living Dimensions on a Module

Brick and concrete masonry offer a system of measurement offers one example of  the use of simple, actual dimensions.  Material sizes are incremented to a module.  In the case of brick, a standard unit is 7 ⅝” long, 2 ⅔” high, and 3 ⅝” deep.  Add ⅜” mortar joints and stack three high, and the face module becomes 8” x 8”.  The corresponding concrete masonry module is 8” x 16”.  An elegant progression of dimensions becomes available as they are assembled: 8”, 1’-4”, 2’-0”, 4’-0”, 6’-8”, 8’-0” and so on.  These are not nominal dimensions, they are precise, with no leftover fractions to build up and keep track of.  Precision, to an 8” module is useful in both concept and detail, in resolving plan and elevation.  Many of the overlapping systems in a building design lend themselves to modules, Regular structural grid modules help set up useful basis for efficient subdivision.  Finish materials frequently come in set lengths that are useful to repeat.  Dimensional modules at various levels provide a framework at for consistent size, shape, rhythm and scale for the building as a whole.  A complex system becomes simple and understandable.

The flexibility of the tools in Revit for producing a design open up new ways for coordinating dimensions at all phases of the process.   In layout, a repeating module of spacing can be chosen to form a series of columns, openings, or room partitions as a rule, and exceptions in spacing made, but kept limited to, say, 1’ increments. (or at smallest, 1” increments). Dimension strings in Revit are “live.” (Here's a good post).  Move a wall, the dimension reading changes, touch a wall, and the dimensions “go live” and can be overwritten with the desired number to move the wall.  Precise placement of elements comes easily, and locations will lock into and flex along a module instantly.  In AutoCAD language, you would force movement increments by a “snap” setting, but these dimensions are on steroids. 

Dimensional Reality of the Model

Rules of thumb abounded in the days of hand drafting.  After the sketcher sketched,  the presenter presented... loosely, in terms of accuracy.  Then, work passed on to the drafter for tedious scaled delineation, with strings of dimensions added at the end of the process.  These were exhaustively solved mathematically, if not geometrically. Towards the end, the drafter often had  to depart from scale to some degree to avoid too many painful erasures, applying the dreaded NTS (not to scale) notation next to the offending dimension.  CAD revolutionized graphically scaled accuracy in architectural drafting. Moving, stretching, erasing, redrawing of geometry was seamless, if not endless.  But CAD brought with it the Boogeyman of  Myopic Accuracy now possible, way beyond any tolerance possible in the field. Endless strings of any complexity of dimension could be resolved in detail to any fraction of inch.  A quick and spontaneous initial schematic CAD drawing was frequently too sloppy, using rough placement to keep thoughts uncluttered, just as in the days of the handmade presentation. Detailed drafters simply threw that work out and started over for working drawings.  

A new era has dawned.  The process of parametric modeling brings us back to reality, to the.concept of resolving to simple, yet precise dimensions, from beginning to end.   Using this logic of modular “snap” points can speed earlier design thinking, and still  remain valid through later refinement.   The whole forest comes into view, reinforced, not obscured by the sheer number of trees that make it up.  “Live” parametric dimensions can give an ongoing reading to the design team giving shape to the building, working elements to a coherent, guiding dimensional pattern. As more detail oriented thinking evolves, more refined, fine grain dimensions help describe the work, building on the original framework.