Every estimate or quantity takeoff needs to checked. Either by the estimator himself or a fellow estimator. The accuracy of the quantity takeoff directly determines the profit margins and chances of winning the bid. Ideally a different estimator should check. But if you must do it yourself then….
Take a break!
I suggest taking a minimum 15 minute break after you finish doing an estimate. Its important to clear your head before rechecking. This dramatically increases the chances of noticing errors or picking up new information.
But what will help even more is a structured method of checking that insures you don’t miss anything.
Start the Checklist with the Basics
There are many things that should always be part of any checking process.
1. Check the Drawing Scale on each page - This is by far the most important task. It is tedious but do not skip it. Also, always check both horizontal and vertical dimensions of the scale. Sometimes one direction can be correct while the other is off.
2. Write the complete scope of work of the project. Inclusions, exclusions and RFIs or doubts.
3. Check that the plans are the latest set. If you download from a online plan room then you may need to go there and check if any latest addendums or plans have been issued. If the job itself had multiple plans, then check if you used the latest ones.
Identify Common Errors
Everyone makes mistakes. That is certainly true in estimating. Notice errors that you correct when checking and write it down. Do this for some time. Use this list to add to your Takeoff Checklist.
These items may be very general. Example - scan the drawings to notice areas where nothing has been taken off but should. Or they may be very specific. Example - check the height of at least one wall on every floor or area.
Refining the checklist process
It is important to not make the checklist or the checking process so long that you are simply doing the whole takeoff again. Checking should be a quick way to eliminate the most common errors.
Checking should take less than 10% of the takeoff time. You should recognise that a lot of things are connected in a takeoff. i.e. they use the same information.
For example a multifamily building probably has a number of different unit types. A good way would be to check the takeoff of only 1 or 2 different unit types and not all 57 of them. The rest you may simply scan visually to see if any area is missing the takeoff. If you got all the materials right on one of them, you almost certainly got them right on all of them.
Always continue to add to the checklist as you find new errors.
How to use the checklist in a team
Today, it is very easy to simply create a shared google spreadsheet or some other document. But more important than the checklist itself is the checking process. In a team I would suggest to use a peer checking system along with the checklist.
It is also necessary to promote feedback (in a constructive fashion) by the checker in case errors are picked up. This will automatically ensure everyone improves and also stays on the same page.