Onscreen Takeoffs: Making Efficient Use of Digital Overlays in Estimating

Ramani Sundaram
For an estimator, overlays are handy for many reasons, whether it's for comparing a design development drawing with a construction documents drawing during design phase estimating or comparing a base contract drawing with a revised version for change order estimates.

Most digital takeoff software programs currently available in the market come with an 'overlay' feature. Using overlays, drawings can be compared quickly and accurately avoiding errors or omissions that may occur if done manually. The takeoff software allows the user to overlay one drawing over another drawing and the resultant drawing shows additions and deletions in two opposing colors. This digital overlay drawing can be saved as a separate file.

Using overlays, drawings can be compared quickly and accurately avoiding errors or omissions that may occur if done manually.

With the contrasting color codes, one can understand changes easily. Some programs also offer other forms of overlays like placing one drawing over the other like a transparency. This type of overlay may not have opposing colors. Another type is a side by side comparison of two drawings. Overlays work as digital light tables for comparing drawings. 

Overlays also help to compare and understand floor plans of different levels in a multi-storied building, differentiate new work vs. demolition in a renovation work, compare routing of new underground utilities vs. existing, etc. Estimators can leverage and make efficient use of this feature for quantifying the changes and pricing them.

Change Orders

Change order estimating is one area where the estimator can make the best use of the overlay feature. The estimator will be able to perform separate takeoffs for the 'additions' and 'deletions' and prepare the change order estimates.

The overlay feature even picks up text changes that our eyes may miss! In a revised drawing, dimensions may be changed, drawing notes may be modified and item size may be modified, for instance changing a pipe diameter from 2” to 3”, etc. All such text changes become more noticeable in an overlay drawing. Especially in a lengthy 'door schedule' or 'finish schedule', identifying the changes manually is tricky but is made very easy by the overlays. Usually designers use clouds or bubbles on the revised drawings to indicate changes. Sometimes the bubble may be missing around the change in a revised drawing. The overlay will make the changes visible even if the drawing clouds are absent.

If there is a discrepancy between the contractor’s quantity and the owner estimator’s quantity, overlays are very helpful during reconciliation meetings. 

If there is a discrepancy between the contractor’s quantity and the owner estimator’s quantity, overlays are very helpful during reconciliation meetings. Overlay PDFs can be projected over a screen, allowing the estimator to explain the basis of the quantity takeoffs. There will be no ambiguities and overlays will make the scope clear to all parties involved in a change order negotiation.

At Faithful+Gould, we have extensively used overlays for doing change order estimates on some of the large projects including the New York – New Yankee Stadium, Madison Square Garden, Lincoln Center, Sheraton Hotel Renovation, World Trade Center, etc.

Design Phase Estimates

The estimator can realize all the benefits as explained above under 'Change Orders' during design milestones from the 'concept' to the 'Construction Document (CD)' stage. Overlays make it easy for the estimator to explain to the owner or design team any cost change due to drawing or quantity revisions at every design stage.

Products

At Faithful+Gould, we use On Center as our digital software for takeoffs. PlanSwift is another software used in some office locations. There are additional products available in the market such as Blue Beam, eTakeoff, ConEst, etc. When we compare the different onscreen takeoff products available in the market, each may have its own limitation and the ease of use may differ. Some programs require the original PDFs for overlay comparison but others make it possible to overlay even scanned documents, sketches or skewed prints.

Choosing the right software depends upon one’s requirement and of course the cost.

If the software is required primarily for overlays, see if the program supports batch overlays which allows overlays for multiple drawings as a batch instead of one pair at a time, is able to create more than one layer over an existing drawing, support different file formats, and so forth. Overlay is just one of the features available as part of a takeoff software. A product that has a very good overlay may lack other useful features that can be found in different products. Choosing the right software depends upon one’s requirement and of course the cost.

In addition to some of the uses listed in this article, a tech savvy estimator may be able to discover more ways of using the overlay feature. The software products available in the market also release frequent updates overcoming any limitations in the current products like ease of use, clarity, etc. Estimators who are not familiar with overlays will begin to appreciate its true value, the moment they start using it.