Working Drawings: Leading by Example

Consulting-Specifying Engineer.  February 2000

When it comes to interpreting poor working drawings, one would be hard pressed to find a contractor who agrees with the engineer-or even an engineer who agrees with another engineer, for that matter-on what the documents mean. All, however, would agree on one thing: bad drawings cost engineers time and often money.

Properly constructed working drawings go a long way to prevent such communication problems during a project. The key is to be able to identify the pitfalls of poor drawings and know the solutions to overcome them. This is especially important for less experienced engineers and contractors.

IDENTIFYING TROUBLES

Although broadly defined, poor working drawings often exhibit fundamental problems: incomplete details, missing drawings, component-sizing errors, poor workmanship, excessive information and nonstandard symbols. Even completely accurate, fully detailed drawings can be problematic if unprofessionally executed, sometimes leading to subtle but significant impacts, most notably misinterpretation.

Avoiding this scenario should be at the forefront of every drafter’s mind because when a drawing is missing elements, it makes jobs more difficult to bid and build. Incomplete drawing sets pose a special problem because omissions may not be obvious. For instance, when details are missing from the end of a drawing set, their absence may not be noticed until construction of that area actually begins. In this case, the contractor would have to proceed without direction or wait for drawings to be developed.

Similarly, incorrectly sized components can be immediately evident or lurking insidiously. As an electrical load in a finished building reaches the design level, for example, undersized components may reveal themselves as nuisance trips for equipment or conductor failure. Fortunately, as long as short-circuit protection is adequate, corrective actions are straight-forward, but still annoying.

On the other hand, the issues accompanying oversized components can be more complex. For example, an over-sized transformer or conductor, though uneconomical, should not cause problems. However, an oversized overcurrent device can be an invitation to failure.

READABILITY A RESOURCE

Misinterpretation of drawings can cause similar dilemmas. Confusing line styles and weights, unclear leaders, crowded symbols and lack of coordinated details all contribute to poor appearance and can mask the drawing’s intent. For example, if existing equipment is demarcated with narrow-weight lines but those delineating new equipment are drawn with lines only marginally thicker, the distinction can be easily lost. Likewise, a misplaced leader could indicate removal of distribution equipment when, in reality, the target was an adjacent outlet.

Crowding is becoming a more common contributing issue to poor working drawings especially with the increase in power and data networks. Traditionally, combined power and system plans were produced at one-eighth scale. Today many projects demand one-quarter-inch scale. This can be problematic in that once a plan is begun at the smaller scale, there is always reluctance to rescale it, resulting in a crowded and difficult-to-interpret drawing.

Five Legal Consequences of Sloppy Drawings

Experienced engineers know that any time saved by producing a sloppy set of construction documents is more than compensated for by time spent correcting the problems and by ensuing liability risks. Five common legal issues are typically associated with poor construction documents:

Permit hassles. Sloppy or absent details on construction drawings often lead to questions by design team members, delays and rejections in the construction permit process. There may be legal liability for delays in issuing a permit due to questions or problems with plans.

Coordination Problems due to bad details may make it difficult for the architect to perform its coordination review. The guilty engineer may have to spend time answering the architect’s questions or redoing portions of the drawings. There may be legal liability for construction change orders due to coordination problems.

RFI’s. If the details are missing from drawings, the contractor is likely to request the left out details later. The flurry of requests for information (RFI) always seem to arrive at the least opportune time-more than making up for any time saved by the engineer’s hasty preparation.

Substandard construction. If plans are ambiguous or lack detail, the contractor is likely to take advantage by cutting corners or cheapening the work and placing responsibility in the lap of the engineer. The guilty engineer may have liability for part or all of the cost of repairing or replacing improperly done work.

Construction claims. The contractor is likely to claim that it bid the cheapest and lowest quantity of work that could arguably be required by sloppy or incomplete construction documents. When design professionals interpret the intent of documents requiring more expensive work, the contractor will often file a claim against the owner, who may in turn assert the claim against the responsible member of the design team-often the engineer

Unclearly or incorrectly referenced details are no better and perhaps worse as they cause contractor to either ignore the details or spend extra time sorting them out. Either way, the owner is shortchanged and usually holds the engineer responsible.

Another cause for confusion is the prevalence of nonstandard symbols found on construction drawings. Unusual symbols could affect the review or could cause a contractor to incorrectly bid the project. A good reference is the American National Standards Institute’s guide to standard symbols for commonly used elements that is available with most computer-aided design (CAD) programs.

The advent of CAD has created an environment in which more information can be placed on a drawing simply by attaching files. By using existing files that include extraneous information, a simple five-sheet design can be expanded into a 15-sheet quagmire, as it only costs the engineer extra paper. Additionally such attachments initially save the engineer time because little work goes into deleting extraneous information and consolidating drawings. Superfluous information, however, clouds the design intent, and should be removed.

INEVITABLE IMPROVEMENT

A way to prevent this is to create a number of "mini-sets". In the planning stage, engineers can lay out each area and element showing where each plan is to be located, the bounds of the required scope and how each detail, single line and schedule would fit into the document set. The designer is then responsible for staying within the original bounds.

Following this simple step may help avoid many of the problems often associated with poor working drawings. Left uncorrected, these problems can lead to increases to owner costs or result in unsafe installations. On small projects with a few limited problems, the expense is nominal and can be absorbed by the contractor as a cost of doing business. On large projects with pervasive problems however, such extra costs can exceed six figures. Furthermore, unrecognized component-sizing errors can result in the loss of the components or even the facility itself.

SOLUTIONS

How the contractor deals with missing elements can vary. An experienced contractor who is short on time can make an attempt to fill in the blanks. If the scope of the drawing is unclear, he or she can provide a bid qualification, placing the responsibility back on the engineer. Filing the missing element in the "future change order" folder may be a good approach for the short term, but does not bode well for future relations with the engineer or owner.

With incomplete drawing sets, a contractor can no-bid the missing portion, although the downside is that the owner may pay 50 percent to 100 percent above bid rates for these new areas- making for a disgusted owner hesitant to do business in the related to the number and degree of oversizing, assuming all of the related components are protected. Undersized short-circuit protection has the graver consequence of major equipment damage or personal injury. The potential for life and property loss is greatest for this particular flaw and therefore carries the greatest liability to the engineer.

Although not life threatening, an unorganized drawing appearance probably causes the greatest number of difficulties in both bidding and installation. It also has the highest potential for impacting the contractor’s profit. Where drawings are clearly incorrect, the contractor can produce a specific change order. Otherwise, he or she is at the engineer’s mercy since final drawing interpretation is the engineer’s responsibility.

Oversizing Dangers

A turn of-the-century theater overcame life-threatening problems caused by bad working drawings thanks to good luck, but fortune is no excuse for poor drawings and certainly doesn’t prevent liability.

In this instance, an oversized overcurrent device and correctly sized conductor nearly burnt the facility to the ground. Fortunately, the problem was spotted as part of an electrical upgrade involving the replacement of a 400-ampere feeder, consisting of 500-kilo-circularmil conductors from their conduit, it was discovered that no insulation remained. Apparently, overheating had damaged the feeder and the insulation had crumbled when moved.

The stagehand’s practice had been to install fuses in the backstage switch that matched the electrical load of the particular show. The fuses in both the switchboard and the switch were found to have two 400-ampere fuse links screwed back to back inside the renewable cartridge. Although this would not result in a full 800-amperes, it did exceed the device’s 400-ampere capacity causing overheating and a potential for disaster. The stage hand had no way of knowing that the addition of another fuse would cause harm because the facility’s original drawings were misleading.

Thankfully, the only damage was to the insulation. Had the conductor faulted, pyrotechnics like none ever seen before on that stage could have erupted because the fuses were rated 5 kiloamps of interrupting capacity (kAIC) or less, and the fault duty was 210 kAIC. For this theater, inadequate fault duty, as illustrated on the working drawings, went undetected, but, as in all facilities, it had the potential to cause both severe property damage and life-safety hazards. When poor working drawings are the root of the problem, it is often the engineer who is held responsible.

PRACTICE MAKES PERFECT

There’s no one "silver bullet" for the resolution of all the issues of poor working drawings. The prospect for future projects-or lack thereof-could affect approaches to drawing deficiencies. There are few instances where a contractor should be expected to absorb the cost of fixing drawing errors. However, the earlier it is in a project schedule that the problems are identified, the easier it is to find solutions that minimize budget and schedule impacts. Of course, the best goal is to produce error-free drawings to eliminate any doubt.

Copyright © 2002 Cahners Business Information, a division of Reed Elsevier Inc. reprinted with permission.

Website Builder