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.
Note: These materials offer prospective students a preview of how our classes are structured. Students enrolled in this course will receive access to the full set of materials, including video lectures, project-based assignments, and instructor feedback.
Now let's talk about validation and methods for checking for errors. So by starting to validate the actual scale on your drawings where you do your takeoff, your quantity takeoff, make sure the scales are correct because if your quantities are off, if your scale is off, the whole estimate will be off. 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 I use the largest dimension available. Sometimes it might only be the height of a doorway that you know is eight foot. Then that's suitable enough.
But if you actually have a dimension from column to column that be even greater because that's looking like 25 or 30 feet or so. It makes your adjustment much more accurate when calculating that. 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 quarter inch and the scale correction is half inch, you'll have to use a different size scale to measure those dimensions or objects on your drawings. So 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, what have you. And that would include your door schedules, might include your wall types.
Learn Construction Estimating
- Nationally accredited
- Create your own portfolio
- Free student software
- Learn at your convenience
- Authorized Autodesk training center
Anything is a double check always benefits the entire project. After a while, you'll see that you might have four or five items that you'll always check, which would include your scale. And make sure that you test these on a regular basis.
The more you estimate, the more you'll identify some costs that might be out of whack. As an example, as you're using a wrong scale, perhaps your scale is half of what it should be, you should be able to get a gut feeling as to the quantities are not matching up. They don't seem right.
Another good example is when you identify your drawings, it'll probably tell you how large the site or how large the building area is. If you do a double check on all your building areas, all your site areas, it should marry up or match up to what's actually shown on the drawings. These double checks are great to validate your estimate to yourself and the management team.
