Facilities Check List
Practical, step-by-step guides for the busy FM
January 1999
Drawings: What You See May Not Be What You Have
Scaleddrawings are accurate, right? Not necessarily. Horror stories aboundconcerning layouts that could not be installed because the space shown onthe drawing was larger than actual field conditions. Here are a fewpointers to help you avoid some disasters.
- Originals andprints may differ. Prints are not automatically the same size as theiroriginals. When mylar is passed through an ozalid machine to make bluelineprints, the most common form of reproduction for architectural/engineeringdrawings, the heat from the machine may stretch the original. What may be adimension of 32 feet when it was drawn may measure 32′-8″ on the print. Nomatter what the source of a drawing, scale off a long dimension string andsee if the dimension stated on the plan matches what you scale out. If itdoes not, check another dimension string. It is common for a print to scaleout slightly longer than the original it is copied from. It is also commonfor the original to stretch more lengthwise thancrosswise.
- Beware copies. Copier technology has vastlyimproved in recent years. One of the most popular copier features today isenlarging/shrinking. Any office worker can unwittingly distort the scale ofa drawing, especially a small sketch, by adjusting the image size button toreduce and copy a slightly oversize drawing to fit the copy paper. Theoriginal may say the scale is, for example, 1/8″=1′-0″, but the copiedimage is not that scale. The image may have dimensions that are impossibleto measure using standard architectural or engineeringscales.
- Did anyone measure the space? In the rush to getlayouts done, designers sometimes rely on old as-built prints that someonegenerated a few years earlier, rather than visit the field and measure theactual space. Field measurements before every job are a must. Your drawingsshould also require contractors to field measure space, even if you havedone it yourself.
- Taking Liberties. In the rush to makelast-minute minor corrections to drawings, architects sometimes calculatecorrect dimensions but do not draw them exactly to scale, especially forminor modifications on non-computer-generated drawings. Sometimes,discrepancies of a few feet may result. Conscientious revisers may add thenotation NTS (not to scale).
- Marketing Brochures. Buildinglessors prepare visually elegant but grossly mis-scaled floor plan drawingsfor inclusion in marketing brochures distributed to potential tenants.These drawings are notoriously inaccurate for purposes of planning spacelayouts. If you need a drawing of such space, insist on a print of thearchitectural floor plan from the construction set, and check a dimensionstring as described above.
- Human Error. One of the mostcommon problems is taking a measurement from the wrong point. The drawingmay be scaled and printed properly, but the reader makes an incorrectassumption about what is actually being measured. Make sure you read thedrawing carefully and know precisely what is beingdimensioned.
- CAD Drawings. Computer-aided design systems,especially the more sophisticated ones, produce drawings developed frommathematical coordinates for each line and figure. Software is designed tostore these coordinates and generate a drawing at any scale, includingnon-standard scales, to fit drawings to various output paper sizes. Noother medium offers this capability, and it changes the way drawings areused. It is essential that when you examine a CAD drawing, you check to seewhat its scale is. Check with a dimension string, as discussedabove.
With these precautions in mind, you should be able toavoid some awkward space misadventures and keep happier customers!
This installment of FM Check List is adapted from BOMI Institute’s BuildingDesign and Maintenance course, < www.bomi-edu.org/12061.html), a requirement in the Systems Maintenance Administrator (SMA) designation program.
