2 Mar

Ductwork: Custom Built China in a Bull-Pen

The construction industry is a strange mix of comraderie and betrayal; I’ve sometimes thought of a job site like a pirate ship: everyone has a job to do and is signed on, by contract, for their share of the loot.

Sheet metal contractors, however, have a specific challenge. Most don’t understand that this is one of the few construction trades where most everything is still hand-fabricated from raw material, be it sheets of metal or 5 ton coils. In that sense, it’s a trade in which there is a double-exposure: whatever must be installed must be fabricated and whatever cannot be installed is garbage. Margins are slim, potential liabilities are large, you’re usually longest on the CP (or really should be), you’re often paid late – and sometimes not at all – and just being the guy trying to get the biggest thing in the ceiling comes with it’s own unique array of headaches.

Every trade convention I’ve been to had a group discussing the importance of construction pre-planning. It’s curious that it just isn’t something that is done often enough in the sheet metal HVAC trade, but having been involved in project management myself, I can understand why. The seemingly endless coordination meetings and heavy investment in drafting software necessary to stay abreast of coordination requirements cost a lot of time and money for a trade where most of the work of coordination ends up being done in the field. A great many installs end up being field-measured throughout. But just as roll formers and plasma tables have fundamentally improved how the trade is fabricated in the shop, sophisticated pre-construction planning through modeling decreases the heartaches of our make-what-you-install trade.

The power in building information modeling for mechanical trades is really in the accuracy of coordination. Having the structural steel understood and every potential collision known and roughly reconciled before subcontractor mobilization means a lot less time figuring out solutions to problems and more time building. 3D / BIM coordination products are slower to produce but result in exponentially better pre-planning that is less prone to error than two-dimensional coordination efforts. This stage of pre-construction coordination also helps greatly in critical path modeling, as workflow and trades stacking in critical areas can be planned out far in advance. While these basic coordination requirements are usually the responsibility of the general contractor, any savvy duct fabricator would do well to make use of these assets and review them in-house or have a trusted outside sub who can handle that aspect of the work for them.

That said, the most exciting usage for BIM for our trade is in fabrication and installation after modeling. Contemporary software can work down to very precise levels of detail, streamlining installation and allowing for the design of specific duct items, such as offsets, transitions, and custom elbows to reduce the overall number of fittings required. Reliance on coordination with structural and other trades directly into the model prior to ever hitting the jobsite allows fabrication without delays or fears of waste, improving shop productivity. With a fully detailed, ready-to-install model, most popular software can then export into multiple formats for CAD/CAM systems, thereby enhancing shop productivity and eliminating unproductive hours spent on field measuring and equipment programming. Production and installation costs can be trimmed. A detailed plan set can let installers loose according to the shops, with few surprises.

While certainly impressive and definitely valuable in it’s own right, my personal experience is that taking the effort to put forth highly coordinated shop drawings is viscerally satisfying when it changes the entire on-site dynamic. All contractors have wasted many hours wrangling over the Whodunits of mechanical collisions, the negotiation of who should move what and how, the fight for the change order, and then ultimately doing the work anyway just to stay on schedule. I suspect most of you know too well the vanity of hoping that someone will actually cough-up the cash to pay you for the privilege of having fixed their boo-boo. The truth is just about everyone else on the job site has a financial incentive to screw you over. But when you have this lovely coordinated, detailed, reviewed, stamped, and transmitted to all and sundry plan set in your hands, you have a shield with which to defend against the claims of others. And you have the ammunition you need to fight for the compensation and extensions of time you are due for having to deviate from the model.

It has been my glad experience that no greater joy hath a wrangler of tinknockers than to stride manfully into an all-trades-on-deck coming-to-Jesus MEP meeting and slap down his build set and its transmittals. It’s enough to vindicate your “…and I wanted to be my own boss…” thoughts. But that gratification, and all arguments of likely financial and efficiency gains, aside, the other return on this investment is the personal satisfaction of a job better done. The frustrations of this profession is the three-ring-circus of assembling a new team for every new project; the rewards of making it look easier and of cultivating a reputation for precision, workmanship, and quality of craft cannot be understated. If you’re going to be anything, be your best.

However, like anything of value, integration of BIM into your business isn’t simple. this is something which must be developed and cultivated. Thus, I encourage you to begin with smart, regular steps. Ask questions, do research, and stay informed of the technology available; in a deep and complex field the best initial step you can make is to partner with an established consultant to shake out your first few BIM projects. In an intensely competitive field where every hour of labor must be put to profitable work, you owe it to yourself and your employees to make use of every available tool.
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