This month, for our ongoing discussion of "making mistakes" in the estimating process, we'll take a look at one of the most common types of mistakes: misinterpretation.
Don't leave home without itAs stated in last month's column, good old common sense plays an important, essential role in the process by which a comprehensive estimate is produced-much more so than we appreciate. Knowledge is a fine thing, but without the application of common sense complimenting abstract thought processes, it is just so much information. As my favorite philosopher, Albert Einstein, once said, "Imagination is more important than knowledge." Common sense has a lot to do with the use of one's imagination-particularly where it is used to correctly interpret details, conditions, etc., typically encountered while performing a quantity survey whereby the primary task is the correct interpretation of the two-dimensional design drawings.
A fairly common example of an interpretation mistake in estimating concerns the manner by which an important type of delineation: elevations (both interior and exterior) are presented on architectural drawings. It is fairly easy to determine the orientation of an exterior building elevation when they are defined by: front, rear and sides, even when a plan/RCP does not make specific reference to the appropriate elevation by way of an indicator or target. Typically, the front is where the building entry occurs-usually on the ground or first floor. With this piece of the puzzle in place, it is quite easy to determine the rear and side elevations. However, for determining a building's exterior elevations by compass direction (N/S/E/W) without the benefit of plan/RCP indicators, a little more interpretation is called for-thus the increased chance for a mistake to occur.
First, we must distinguish "True North" from "Project North." This is normally found on the drawing legend; on the right hand margin near the drawing's title/number. With Project North established, defining the building's exterior elevation orientation can commence since, as the front elevation defined, the remaining elevations, the north elevation provides the key to defining the balance of building elevations by compass direction. Now comes into play the important distinction between the common words "from" and "to." A building's exterior elevation is oriented from the compass direction-not to the compass direction. For example, the North elevation is taken from the North looking to the South, not from the South looking to the North.
Likewise, the other exterior elevations are established in similar fashion:
o South elevation is looking from the South to the North
o East elevation is looking from the East to the West
o West elevation is looking from the West to the East
Now, for Interior elevations, such as for rooms, corridors, lobbies etc., the very opposite interpretation applies. An interior space's N/S/E/W orientation is to the compass direction, not from the compass direction, as it is for an exterior elevation. Thus, a room's North elevation is taken from the South looking to the North. As well, the other interior elevations can be established thus:
o South elevation is looking from the North to the South
o East elevation is looking from the West to the East
o West elevation is looking from the East to the West
Aside from establishing the correct elevation/orientation, it's also important to coordinate it with the plan view. This will allow one to account for any/all setbacks, recesses, niches, indents, curved surfaces, etc., that the elevation view does not highlight. The referencing technique of profiling (discussed in a previous column) helps greatly in distinguishing these features onto an elevation. In effect, the profile superimposes a plan view onto the elevation itself.
Of course, as mentioned previously, the best and easiest way to establish an elevation-whether it be interior or exterior-is by use of an indicator or target on a plan/RCP referring specifically to a particular elevation.
Typically, these indicators are present (but not always) thus you must know and appreciate the subtle but important differences in interpreting a given elevation as discussed. Likewise, knowing this allows you to double-check the architect. It is not uncommon for elevation indicators to be mistaken and confused. Aside from understanding the orientation criteria, another good way to double-check or determine an elevation's true orientation is by way of column line indicators. Most often, column lines are indicated above the elevation itself-particularly for exterior elevations. By coordinating the column lines on the elevation with those on the plan, the correct view in elevation can be easily/quickly determined/verified.
Next time for our ongoing discussion of making mistakes, we'll continue on the subject of interpretive mistakes with what would make Mr. Spock and the planet Vulcan proud: applied logic.