Estimating Accuracy- Part 1 (Jan 25)

A couple weeks ago, a support call came in from a potential buyer of our construction estimating software. They were confused, because the math seemed wrong for one material line item in an Assembly. When we checked it in our copy of the Sample Company File, it definitely was wrong. The line item total should be equal to unit cost times quantity plus waste factor, and it wasn’t.

It took a while to investigate this problem, and I’ll get to that later.

First of all, you can do the following to fix things:

  1. Choose Cost Items from the Costs menu.
  2. Choose Find All from the Edit menu.
  3. Choose Replace All from the Edit menu.
  4. In the Replace popup field, choose Adjust by Percentage.
  5. Type in a small percentage like .0001%. Or use a bigger number if you want to account for inflation.
  6. Click OK.
  7. Goldenseal will recalculate all Assemblies, and redo all the math correctly.

Actually, this adjustment fixes everything except for four items: all for unskilled labor in closet shelving. We still need to investigate why that is off. Right now, even after the Replace All update, it still calculates $6 to $12 too low per closet. Everything else is fine. There may be a reason why closets calculate that way, but if so, nobody here remembers why.

We did not find anything wrong in the code that calculates unit costs in Assemblies and Estimates. You also won’t see errors for materials if you’ve changed their purchase price, or if you used a percentage adjustment any time in the past. Those force the Assembly line items to recalculate.

Right now, we still don’t know exactly how the numbers got off in our construction estimating data. We have tried hard to duplicate the problem, but so far it never goes wrong in real time.

The Sample Company File has been around since the early, pre-release versions of Goldenseal. That’s why most of its contents have dates in 1998. We used it for daily testing. Back then, the file format changed frequently, so we exported the sample data to a text file, then imported it back into newer versions. It was faster than retyping the fake business records.

Most of the construction price data came from our older software (MacNail, HyperEstimator and BidMagic). Converting those to Cost Items and Assemblies required some hacking and export/import. As we improved the estimating process, there was more hacking and export/import. Then we moved data between the sample and starter files, which meant even more hacking and export/import. Lots of opportunities for errors to creep in.

Over the years we have discovered and fixed a few dozen unit cost problems. Users have also reported a few. I suspect that the rest of the data bugs have lingered there unnoticed since the late 90s or early 00s.

The errors are almost exactly balanced between positive and negative. In real world estimates, they probably canceled out. Most are just pennies, probably from rounding errors. The big ones are in obscure materials that we don’t update very often. Anyone actually using them probably entered a new price, which fixed the math.

Still, we sell data as well as software. It should be perfect. We are working on that now.

While testing the construction assemblies in our estimating software, it also seemed time to update the material pricing. In general, wood pricing is up, concrete is way up, while hardware and manufactured items are down slightly. There are still more prices to gather, but updated files will be available for download soon.

Digging around in our construction cost database stirred up some other issues that are worthy of discussion. I’ll cover them in a future post.

Dennis Kolva
Programming Director





Author: Dennis Kolva

Programming Director for Turtle Creek Software. Design & planning of accounting and estimating software.