Wall Schedules and BIM

[phyllisr]

Question #1
Has anyone successfully used calculated values to generate quantity totals that might be used successfully for GWB quantities, paint quantities, VWC or any similar items wherein the sides of each wall might be different? I have been able to generate the calculated values to get both sides of the wall but have not found a way to differentiate which is which.

Anticipating the questions about why I would want this level of detail and is this not the contractor responsibility (a valid point), I am looking at this as a BIM issue and a partnering issue. The possibilities are in front of us now - I only want to plan ahead, anticipate the future and insure we are ready. AIA Contracts, insuring agencies and more will follow eventually.

Question #2
Has anyone tried Uniformat classifications combined with formula properties, filtering and more to generate a wall schedule that will return information on components? Unless I am misinterpreting other discussions on this topic, it appears impossible to extract information about components within a wall family and generate a schedule with quantities. Should I wish to know, for example, how much total sound batt insulation there is in the entire project, it appears that cannot be done. I have been thinking about a method to use Uniformat to separate and identify (for example) all the walls with a particular number and collect the information that way. If anyone has tried and failed, it would be helpful to know so that I do not spin my wheels.

Question #3
Has anyone determined in detail how the program "thinks" when calculating SF and area information? I am hoping to avoid hours with a calculator and lots of experimenting trying to resolve this on my own.

I discovered quite by accident (and going a little crazy trying to determine why a 5'-0" wall that is 10'-0" high was returning an area SF of 49.38 - attached clip) that Revit appears to calculate areas allowing for wrapped ends and corners. Which side and why? Is it related to the location line position? If I have a simple 4-wall room, is the area returned for the interior or exterior? Can I control this calculation? What if I want both sides and to know which is which? The wall family has an interior and exterior each side of the core - is there a way to access this information in a schedule?

Again, anticipating the questions about why I care about a few decimal points, this is not what I am trying to resolve. I am hoping to use your collective experience (much greater than mine) to help understand why and how only for the knowledge base.

Thank you all in advance.
PBR

[rrijswijk104343]

As far as I can see the area is calculated by:

area = length * height

length = wall centerline

i hope this helps...

I think the better way to do this, is using Material Takeoff
Also, check how the walls are joined together...

When drawing a square room from 1x1 m2 , it appears that the first and the last wall have different wall length due to drawing order. Just play something with that wall end and you will see that all the walls from your square room have the same length/area/volume

Greetings, Renzo

[Mike Sealander]

Phyllis:
I think you are right on to inquire about take-offs in the manner you are. Any design-build firm, from "guy and a truck" on up to Bechtel would want this, let alone architects looking to sell value-added in a design-bid-build project. If you find out more, please post.

[cphubb]

The walls do count the inside and outside material differences. Experiment, take 2 walls 10' long and join them. The takeoff shows 102sf and 104 sf for one and 98sf and 196 sf for the other.

Change the join type to miter and the amounts are 102sf and 201sf for both walls.

We have also noticed that by cutting materials with voids that only partially cut the wall we can reduce materials in the takeoff as well

[jeff.95551]

I've found by working with our contractors that they are probably a lot further away from being able to use this than we are from being able to provide it. What I mean is that the estimators are all working with systems that give them a comfort level about their ability to do the work, and the quantity of the material isn't the only, or even necessarily the most important variable. In working with some very sophistocated national builders on cm-at risk style jobs, we provide them with wall and floor schedules (by floor if possible) and the concrete volumes along with the schematic plans (and all of the other basic schedules, of course), and that gives them much more information than they can really use for schematic pricing. I've tried just giving them takeoffs, and without the full context (which they get by doing the takeoffs) it doesn't mean much to them. Hanging drywall on an 8' lid is much cheaper than hanging it on a 13' lid, for example. The takeoffs don't tell you that.

Then there is the human factor - give a set of plans (even with the drywall quantities figured accurately for them) to 12 different subs, and you will get 12 very different prices. They have different markups, different labor rates, different ideas about how to execute the job efficiently, different sized boats that need gas and insurance, etc...:)
Our contractors use the information as a gut check, but never distribute it to the subs.

[robert.manna]

I have to confess that I find any area numbers related to walls in Revit very suspect. There are so many variables related to how one can begin to model walls (espcially interior partitions and even exterior walls) that I just don't trust the numbers. For calculating interior partion finish area (or any amount of area) I would be more inclined to take the linear value of wall and multiply it by a set factor for height. As to exterior walls I would be inclined to use material takes offs, if I know that I've been very disiplined about using my exterior material types. I honestly think we have quite a way to go before I'm inclined to trust wall area numbers. As to taking linear feet and multipling (for interior partitions), you coud easily add a shared parameter (or your wall type name or mark might be usable) to determine and filter if wall's finish material extend to ceiling (or slightly above) or if the full wall extends to the underside of deck. From which you could determine what factor to apply to multiply the length by and get an area. While this is not a perfect system, it strikes me as being more accurate than attempting to use areas (especially when you take into account that a wastage factor needs to be applied to any amount), and in certain ways allows for the flexibility that Jeff talks about (ie is it cheaper to hang the GWB one way or another).

edit: (In smaller or medium size firms where you can exersize tight control and disipline over the project teams, you might succeed in establishing a set standard for modeling walls. But with 600+ people, I doubt that we will ever achieve that level in my firm, to a degree certainely, but each project will be unique, and it will be up to the project teams how to best proceed.)

Even when I re-did my kitchen and had a Revit model, it was far easier to actually measure, and determine quanities then go back to my model and attempt to extract all the quanitty info. Though the floor areas were pretty close..... :)

My 2 cents,
-Robert

[Mike Sealander]

Robert:
I think you're right.
In the year I've been using Revit and following this forum, I've noticed that every once in a while someone wishes for something, or sees the potential in something, that would be industry-changing, but in the end just doesn't seem to pan out. Take-offs in Revit and its application in reality may be one of these areas where the industry is still ten years out.

[robert.manna]

Yes and know, I think the low hanging fruit we can use, and will start to use. I trust floor area numbers, I trust area of curtain wall panel (once gain a wastage factor needs to be applied anyway) I trust equipment and unit accounts, and generally trust roof area too. All of this of course assumes that you have a project team that knows what they're doing in Revit. Walls for me as I said, are just so unique, and there are so many little gotchas with walls (and different workarounds that people use) that I just have a hard time trusting anything beyond a linear foot measurement, and that can be useful too. No matter what, adoption will take time, and it will probably be another 20 years, before we see it fully across the board.

-R