Kevin R. Miller BYU Construction Management

Estimating today When 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?

Risk Who bears the risk today if the plans aren’t complete? How do you cope with plans that aren’t complete?

Benefits of Takeoff Process (Traditional Plans) Become familiar with the project Find problem areas and identify risk and constructability issues Value engineering

Down side of Takeoff (Traditional Plans) Time consuming (Detailed Estimates) May miss something Transferring 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 constructable Interference resolved before work in the field starts. Better understanding of design intent.

Model World Today Not the magical pushing a button and the estimate is done. No such thing as a 100% Model Look 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 source The liability that exists with 2D drawings exist with 3D models With 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? Counts Lengths Areas 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.

Methods of Model Estimating Quantity Schedule Quick method to get list of quantities. List quantities typically without visualization of the model. Doesn’t takeoff items that are not modeled. Active Takeoff Navisworks. 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 Model 3D model 2D modeled sheets Allows you to perform takeoff for the things not modeled. DWF/NWC file format

Is this model useful?

Are these model useful?

Detailed Takeoff

Search and Rescue

Everything

Model prep hints If 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 Classroom Takeoffs 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.

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