Accuracy is everything in construction estimating as any mistake can hit either the top line or bottom line directly. Based on my 15+ years of estimating experience training and managing over 100 estimators, I have complied a common list of errors. Some are made usually by trainees but other are made even by experienced estimators.
11 Common Construction Estimating Mistakes
- Scale - Forgetting to set the scale or not checking at least one horizontal / vertical dimension on each and every page can lead to scale errors.
- Only using elevations for exterior material takeoffs - Exterior items / materials are often taken off in elevations. However, depending on the plans there can be hidden elevations or elevations shown multiple times (either partially or fully).
- Calculating no. of floors incorrectly - Large multifamily projects or tall buildings often have the same floor repeated. How many floors between Level 10 and Level 28. A common error is to subtract 10 from 28 and count 18. However, the actual number of floors is 19. Also, some buildings don't have a 13th floor.
- Not checking site plan - Checking the site plan is essential to avoid missing scope of work. Sometimes plans / building may be repeated and only shown
- Dealing incorrectly with discrepancies - Construction plans are far from perfect. Often there is a mismatch in information given in 2 different places for the same thing. Either an RFI must be raised, or a logical assumption must be made and flagged at time of bid submission.
- Not identifying that plans are missing necessary items - Sometimes items or information will be missing in the plans and specs without which the construction cannot be completed. In such cases experience and presence of mind is required to understand and avoid the mistake. Remember, even if its not your mistake there can be liability thrust on you because that is human nature.
- Not highlighting information as you find it - This helps with checking the takeoff and dealing with addendums and change orders which inevitably come.
- Not qualifying the bid / estimate correctly - If you do not source / manufacture certain items or if you have made any assumptions, it is extremely important to communicate them at the time of bid submission.
- Calculating waste incorrectly - Typical waste calculations may not work due to size or type of material or peculiarities of the project.
- Focusing only on quantities while ignoring execution complexity (labor cost) - Estimates usually use material quantities to calculate labor as well using productivity tables or estimates. However, in some cases labor can be the dominant cost and the calculation process need to estimate labor as the main / separate cost and add material cost on top. This usually happens due to increased complexity of construction.
- Forgetting to change or put height / depth in takeoff condition - This is an estimating software quirk. Estimators will understand what I mean.
How to Avoid Estimating Mistakes
Peer Checking
The number one thing that ensures accuracy in our company is getting the estimate checked by a different (usually more experienced) estimator. I suggest implementing the same process in your construction firm
Checklist
Having a checklist helps to avoid mistakes as well as catch them. Even if the checked is the same as the doer. See my blog on creating a checklist.
Scope of work Document
Preparing a scope of work document at the end helps both quality the bid but also the best way to avoid big errors in the bid.
Creating an excel template with formulas
Converting a takeoff to a bid can also involve errors. You can cut down on them by creating a template to do that. Either do it yourself or hire an excel expert to do it for you. It is a onetime investment that will pay you dividends for a long time.