Friday, November 12, 2010

Concrete Volume Scheduling - Cautions

Recently I was asked to schedule the concrete volumes for a building that had been modelled in one of our other offices.

The task was fairly straight forward, schedule every concrete element in the building to obtain an approx concrete volume for pricing. In todays competetive market it is essential to be as accurate as possible with your estimates.

I decided to start with the columns, and almost straight away noticed a problem with the volumes that were scheduled. The volume in the schedule was almost half the actual volume of the column. So, I decided to investigate the cause, and soon found the problem.

We had a wall with a column that was placed at the end of the wall (as shown in the image below)



The wall and column schedules shown below are the initial numbers the schedule produced.





I soon realised what the problem was, the wall was intersecting the column, and it was the wall that Revit assumed would be the prime element, so by default it was cutting the column.

The solution was to move the wall back to but up against the face of the column.



The column and wall schedules are now correct.





I decided to do some further testing, does this also happen with beams?

The simple answer is yes.

If a wall is joined to a beam in the 'wrong' way, then the schedules produced will be incorrect.





The wall should stop at the underside of the beam over.





Is this a problem with the software we use? Maybe. Is this a problem with modelling techniques, possibly.

Either way, this could cause problems on large scale projects that require accurate volume estimates. That said, a disclaimer and the word 'estimate' should cover you to some degree.

I guess we all have to pay that extra bit of attention to how we construct our models if we know we will be using the information rich BIM to schedule quantities and produce estimates.

1 comment:

  1. Very informative. I am newbie in Revit. What about the volume of the slab with beam? Have you check such problem exist? Thank you.

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