Dimensioning For Success - Part 1
Designing and constructing a building is a complex undertaking. Designers draw hundreds of pages to convey their vision. Contractors are experts at bringing that vision to life. But sometimes it doesn't go as smoothly as everyone would like and dimensioning is one area that we think improvements can be made for the benefit of the entire project team.
Designers and construction managers have the luxury of performing most of their work in an office setting. From there they can review and study plans through Bluebeam, full size paper prints, and half size paper prints. Craftspeople perform most of their work outdoors in a physically demanding environment. Asking the craftspeople, ankle deep in mud in the pouring rain, to consult an iPad for the details just isn't effective. They do carry laminated exploded screenshots of the days relevant work area. Even in this age of technology most of the work gets placed from sheets of paper.
In this modern era, buildings have become increasingly complex. Dimensioning to maximize space, accommodate complex assemblies, and to meet code requirements has made just about every inch of the building critical.
However, one element of plan development has remained stagnant: gridlines. Long gone are the days where major building elements were all located on a handful of gridlines. A “simple” corridor can start on grid and move off the gridline ever so slightly for a whole litany of reasons. These slight variants catch installers off guard all too often, resulting in any level of rework.
Our solution is to create an “offset gridline” (quality control master grid line) that we can always reference and measure from. It is a gridline that doesn’t intersect any building element so we can always reference it (never assume) and pull a distance from it. It doesn't come in and out of a wall as the wall jogs. It is not subject to compounding errors created by “doing the math” on several dimension strings. It stays put. With this offset gridline (typically located down the middle of a corridor), we can measure to any wall perpendicular to the corridor quickly and accurately. Better yet, someone can quality control the work quickly and efficiently.
There are several common areas where errors occur. Anytime a dimension is pulled from a complicated building element; face of brick, face of siding, face of shaft wall, edge of counter, can be a recipe for disaster. Centerline of party walls can be complicated. Has the presence of double shear been included? How does the airgap move when shear is present? Sometimes the line weight of the line itself can confuse things, especially when there are multiple lines. These are examples why the idea of an offset grid line that runs across the middle of a room or down a corridor is extremely beneficial for clarity.
That's where the idea of an offset gridline comes in: a neutral, beholden to none, master grid that we can measure from. This is a great way to protect from a lot of the minutiae trouble that arises in trying to identify the critical dimensions.
This is the first of 5 articles that will explore ways of dimensioning a set of plans that can reduce the opportunity for errors.
Part 1 - Overview
Part 2 – Parking Garage and Building Core
Part 3 – Inside of the Building (Rooms/Units)
Part 4 – Inside of the Building (Other)
Part 5 – Outside of the Building