Forums >> Revit Building >> Technical Support >> Material takoff on joined walls

AtisAtis

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Hi,I have a question regarding material takeoff: How is material calculated when wall joins are applied? I have inconsistencies between areas. When i join wall layers and some materials are cut off, the area doesn't match the are that I get from filled region. Please see attached image.

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AtisAtis

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For example, if I copy this wall 24 times, area should be 24x1,5= 36m2 but in schedule it shows 39,266m2!!  It's a 3m2 error! Imagine this for large building... 

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WWHub

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Joined: Tue, May 16, 2006
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Revit looks at several things.  How you define your junctions is one of them.  Material Priorities also affect this.  And don't forget that Revit's working point is the centerline of the material, not necessarily the exposed face.

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AtisAtis

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This is wall to wall vertical join, so mitter, butt junctions doesn't apply here. Basically what I found is that Revit built in algorithms are s#it when it comes to material quantity calculation. And they release new verions every year with bunch of nonsense features while base calculations are done with Minor discrepancies....

Note: When Revit computes the volume of materials for individual layers within a wall, some approximations are made to maintain performance. Minor discrepancies might appear between the volumes visible in the model and those shown in the material takeoff schedule. These discrepancies tend to occur when you add a sweep or a reveal to a wall, or under certain join conditions.

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/Revit-DocumentPresent/files/GUID-F8270A42-CA71-46C7-B145-85EC2CB8E4A1-htm.html

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WWHub

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I really don't have a problem with this.  But then, I worked in the office for a construction company while attending college.  I worked right next to the estimating department and watched and learned how they estimated projects. 

Material take offs are NEVER the exact measurement of the face area.  As an example, for tile work, much of the entire perimeter offten has to be cut.  Sure, some of those pieces could be used elsewhere but most times, looking for that piece is more expensive then using a new one.  This is the same for every material.  So the estimator allways applies a waste factor that varies with material. Does this result in excess material ordered.  YES .... but that is better than not enough to begin with because you may not even be able to get additional matching material and a partially used box of tile is non-returnable.

Find another axe to grind because this one is already sharp enough.

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