One of the things I have been preaching more and more about is “Product selection is not product specification” (I am sure there is a text from Leviticus that is applicable). I have been focusing on “work results” when I talk to people, emphasizing that specification addresses issues outside of product selection that can be critical to the project.
“Specs to me in this BIM world is about providing the necessary information in an easily read form continaing only the information needed for the task and nothing more.” This has always been the goal of a good specification. Unfortunately, what is really important at one point in the continuium from insception to realization of a project may be trivial or irrelevant at another point.
By its very nature, BIM will focus more on the physical and performance attributes of an object or a collection of objects. Quality control issues (including submittals, coordination, warrantees, tolerances, field conditions) are not “objects or attributes of objects in a model” (although I suppose they could be), but they may be critical to successful completion of the project.
My time with CAD goes back to the mid-80s. I backed off and returned to spec writing when I say people who used (and developed) such tools were much better computer jockeys than they were architects. Moreover, many mistook computer expertise for real architectural expertise (which is another whole discussion). It has been frustrating to discuss products and work results with such people when they really aren’t interested in much other than the graphic representation.
I would hope that many BIM developers have realized that generating a bill of materials is not the same as generating a specification. Such a list helps (helps more if the nomenclature is correct). The bill of materials is a starting place; does this particular work result require a Product Data submittal? or a Shop Drawings? Are there source quality control issues that have to be addressed? What about preparation before installation? Are there tolearances that must be met?
The bill of materials will probably list a significant quantity of galvanized steel pipe which may be used in a variety of work results including columns, handrails, guardrails, and piping. Plastic laminate may be a common finish material, but the work result may be cabinets or countertops or toilet partitions. Stone may be used for exterior cladding (both in anchored or adhered applications), exterior paving, interior columns, countertops, or toilet partitions. Each of the various types of work results above may require a slightly application of the specific product.
When one looks at all the players on a particular construction project (typically almost 100 even on small projects many more on large projects), each of these uses the construction documents different ways, some very specific and narrow, others very broadly. The plastic laminate manufacturer is interested in how much, what type, and what color products are to be suppled to a cabinetmaker (or other fabricator). The cabinetmaker is interested panel products, adhesives, hardware, and fabrication standards in addtion to the plastic laminate products. Someone needs to be concerned about the schedule and how it gets installed.
Should BIM even address all of this? Depends on which fight your dog is in. The Owner is going to want different things out of the BIM than the roofer wants which is different from what the engineer doing the energy model wants while the guy hanging the doors wants to know if he needs to have wood screws or metal screws.
Traditional construction drawings are in a sense very abstract and they are more economical about how information is conveyed. Not every piece of rebar is shown, but there is enough information for a fabricator to furnish all of the rebar and stirrups that are required. Do we really want to require that BIM fill in between showing a few “instances” and shipping the complete order? I doubt that there is a computer in the country that is really capable of showing every single item required for say an elementary school for 600 students (every nail, every screw, every stirrup, every sheet of insulation board or sheathing, every masonry tie, every masonry unit), but this is what many people are expecting.
If the Drawings show where, how much, what size, and interface between products and systems (think of a door detail showing an interface between a wall and a frame and an operating door leaf), the Specifications carry a different bucket of water (materials for each assembly, performance requirements, and tolerances as well as quality assurance, field conditions, warrantees, and finishes).
Is BIM really able to carry the burden of all of this information, or are BIM developers going to discard as irrelevant items that pose different levels of difficulty? This is very much like the CAD monkeys I have dealt with, secure in their own skills, who simply will not face up to the fact that it really does matter whether or not the gyp board thickness is 1/2 or 5/8 inches, and furthermore, that they should understand why this matters.
We can build expert systems, we cannot build expert systems that we know will be used expertly.
