Construction Layout: Then and Now

July 12, 2018

If you’ve worked in construction layout — especially in the MEP disciplines — for more than a decade or so, you’ve seen some incredible changes in the standard operating procedure. Some of the “oldtimers” are still getting used to the way layout is usually handled these days, although there’s no arguing these changes are all for the better.

For those of you who may not remember how your elders used to plot a site in preparation for construction, this may seem like a crazy fairy tale. For the rest of us, it’s just a walk down Memory Lane…

The tape measure and the string

Back in the day, laying out a site was never a one-person job.

Instead, it always took a team, armed with the building drawings, a tape measure, and sometimes a piece of string! Height or elevation was measured with a level (you know, the kind with a little bubble in the glass tube?) and a theodolite was used to measure angles. Here’s the Wikipedia page for “theodolite”, in case you’ve never heard of it before.

The team worked from a reference point of known location and elevation to plot where various building services needed to be placed. HVAC ductwork, sewer pipes, cable trays… you name it. Every point on the detailer’s drawing needed to be mapped out, painstakingly, using manual tools and a good eye.

Unfortunately, as you can probably imagine, the system didn’t work particularly well when we needed to layout complex buildings, spaces with curved walls, prefabricated materials, or coordinated models. Which, really, didn’t leave much else beyond the occasional empty, square room.

The need for something better

Decades ago, we didn’t know any better and there weren’t any other viable options to consider. Looking back, though, it’s easy to see that the manual layout process was time-consuming, labor-intensive, and had a huge margin for error. Errors in layout could lead to serious — and expensive — consequences, including clashes with other building services and prefabricated components that didn’t fit properly. By extension, that meant time, money and materials being wasted.

If there’s one thing that hasn’t changed in all these years, it’s the fact that waste and inefficiency will kill any construction firm’s profit margin. So, it only makes sense that the layout process had to change.

The modern MEP layout process

I’ll hold back from spouting the cliche’ lines about how young layout pros have it easy and will never appreciate the old ways… but it’s true.

For most mechanical, electrical, and plumbing firms needing to do layout today, lasers, 3D scanning, and even robots have brought the necessary workforce down to a “team” of one. Working with nothing but a tripod-mounted laser scanner and a laptop or tablet, one layout professional can now do, in one afternoon, what used to take three or four of us two days to get accomplished!

And, the results are a thousand times more accurate and usable.

With a cellular or Wi-Fi connection, the 3D point cloud data that these laser scanners help generate can be translated in nearly real time to a 3D model that’s ready to be manipulated in the software of the detailer’s choice. Then, just as quickly, that model can go on to the fabrication shop, or all the way to the jobsite, with all necessary adjustments updated on the fly — in the blink of an eye.

That’s a heck of a ways from the days of measuring tape and string, and don’t let any bitter old roughneck tell you any different.

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