Model Estimating

Kevin R. MillerBYU Construction Management

Estimating todayWhen was the last time you estimate a set of plans that

were 100%?How do you perform quantity takeoff?How long did it take you to do the takeoffs?When you perform a takeoff, do you look at every sheet

simultaneously?

RiskWho bears the risk today if the plans aren’t complete?

How do you cope with plans that aren’t complete?Hard BidNegotiated, Design-Build

Benefits of Takeoff Process (Traditional Plans)Become familiar with the projectFind problem areas and identify risk and constructability

issuesValue engineering

Down side of Takeoff(Traditional Plans)Time consuming (Detailed Estimates)May miss somethingTransferring quantities from takeoff sheets to Estimating

software tedious and non productive

What do we want from the Model?Accurate quantities.Less takeoff time.Better visualization of project.Subs to understand the project and their scopes.More time verifying what is modeled is constructableInterference resolved before work in the field starts.Better understanding of design intent.

General Sales PitchPush the button.

Costs are generated.The 4/5 D model is generated.All the work is done.

Looks good, sales software.Not necessarily doable without a lot of extra work.

Model World TodayNot the magical pushing a button and the estimate is done.No such thing as a 100% ModelLook at the information that is relevant to your takeoffs, not

everything at once.Your costs come from your historical cost database or bids

not Means or some other sourceThe liability that exists with 2D drawings exist with 3D

modelsWith BIM – Risk shouldn’t change or shift

Estimating from the Model or Not?Do I really want to work from the Model?

No, I want static drawings that don’t change so there is an accurate history of the costs for the project.

No, I don’t want the potential to change the drawings because I’m an estimator, not a modeler.

No, the file size of the model would really slow me and my computer down.

DWF/NWC file (a read-only copy of the model) addresses the above concerns

What can we really get from the Model?CountsLengthsAreas

Be careful with areas and volumes Use Length * Height for areas Use Length * Height * Width for volumes

Do these concerns mean don’t use the model? NO, just understand how the quantities are being calculated.When in doubt, check the quantity calculation.

Timberline OpportunitiesQTO integrates seamlessly into Timberline.

Cleanup and optimize the estimating DBToo much legacy junk in estimating DB’sEvery item in the DB should have a formula in order to link

QTO integrates better with Timberline than Timberline does

Methods of EstimatingSchedule

Quick method to get list of quantities.List quantities typically without visualization of the model.Doesn’t takeoff items that are not modeled.

Active TakeoffNavisworks. Assign model objects to the takeoff.Takeoff objects that haven’t been modeled using 2D takeoff.Visualization of what has been taken off.Ability to override model quantities

What is needed for Active Takeoff from the Model3D model2D modeled sheets

Allows you to perform takeoff for the things not modeled.DWF/NWC file format

Model prep hintsIf there are more than 20,000 objects, things slow down.

If the model is too big to work on your computer, Section it.Then Link the Models.

Most likely you will want the cost by building anyway.

If there are too many objects, turn off the ones that are not being taken off, like curtain wall mullions (9621 Objects) out of 28,015 objects in the entire project.

Estimating in the ClassroomTakeoffs taking less time. Assigning more projects for

takeoff.

Students are understanding what is being taken off better in 3D than in 2D.

Scores are going up and takeoffs more accurate.

Contact: Kevin R. Miller kmiller@byu.edu

Office: 801.422.8728http://cmfac.groups.et.byu.net/miller/