Would your fire your estimators, retrain them, or strongly encourage them to go to work for your competition? Here’s two houses, both built by the same builder, and even both on the same block:
I count 81 extra bundles of roofing on the first and 78 extra on the second. Now, I’m certainly not here to blast estimators. Especially, since I’ve been doing takeoffs on residential construction projects since the 80’s, and definitely had my share of takeoff errors. When I was first starting out, I didn’t have a feel (or even a clue) for spotting numbers that were way out of whack. These two homes each have around 26 or 27 squares of roofing left over on what looks like 45 square roofs. So, wouldn’t you think that a takeoff with 70+ squares would jump out at someone in the chain?
Maybe this is not even an estimator error. Perhaps it could be a process error, a clerical error, or things just got whacked in the options or option-overlap takeoffs. These things happen all the time and can make a great estimator look ridiculous.
Regardless of the cause of these takeoff errors, here’s a dirty little rule of thumb that can red-flag this from happening on your homes … One bundle of roofing per sheet of roof decking. It’s not perfect, but it’ll get you pretty close. This approximation works if you’re using a 3 bundle per square shingle. If not, you can approximate one square of roofing for every three sheets of roof decking.