Explore the importance of scale validation and error checking in quantity take-offs for project estimation. The article highlights how correct scale measurements significantly influence the accuracy of estimates and discusses the role of digital take-off software in calibrating scale.
Key Insights
- Verification of drawing scales is crucial in quantity take-off as any errors can greatly affect the entire project estimate. Testing scales against known dimensions, especially the longest available, enhances accuracy.
- Digital take-off software programs, despite their vulnerability to reduced size drawings, offer the advantage of scale calibration. Manual take-off may require the use of different scales for accurate measurements.
- Regular double-checking of all elements related to costs, such as door schedules or wall types, improves estimate validation. By regularly testing and double-checking, estimators can develop a sense of when quantities don't match up due to scale errors.
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Now let's talk about validation and methods for checking for errors. By starting to validate the actual scale on your drawings where you perform your quantity takeoff, make sure the scales are correct because if your scale is off, your quantities will be off, and the entire estimate will be inaccurate. Let's start this by verifying that all drawing scales are correct.
Test any noted scales to a known dimension, and typically what I do is use the largest dimension available. Sometimes it might only be the height of a doorway that you know is eight feet. That’s suitable enough.
But if you actually have a dimension from column to column, that would be even better, which might be 25 or 30 feet. This makes your adjustment much more accurate. Accuracy improves when the longest dimensions are tested.
All digital takeoff software programs are just as vulnerable to reduced-size drawings. To remedy this, they have the advantage of calibrating the actual scale. If you're doing the takeoff manually, you may have to use a different scale altogether.
For example, if it says that it's a quarter inch and the scale correction is half an inch, you'll have to use a different size scale to measure those dimensions or objects on your drawings. As you're checking the scale on your drawings and making sure that your takeoff was done accordingly, go ahead and double-check everything else that's associated with actual costs or counts, or other related elements. That would include your door schedules and might include your wall types.
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Any double-check always benefits the entire project. After a while, you’ll find that there are four or five items you’ll consistently double-check, which would include your scale. Be sure to test these on a regular basis.
The more you estimate, the more you'll identify some costs that might seem off. For example, if you're using the wrong scale—perhaps your scale is half of what it should be—you should be able to get a gut feeling that the quantities are not matching up. They just don’t seem right.
Another good example is when you identify your drawings—they'll probably tell you the size of the site or the building area. If you do a double-check on all your building areas and site areas, it should match up with what's actually shown on the drawings. These double-checks are great to validate your estimate to yourself and the management team.
