Help! Wall Area Inacurate???

[Devin_82]

I need a little help with wall areas. Below is my situation (sorry for the length, I just wanted to be clear):

So here I am working on some % of opening calculations and I notice the wall area reported in a wall schedule of a wall that has an exterior dimension of 20' and a height of 10' and width of 12" is showing as 190 S.F. This wall is part of a string of connected walls. I draw a new wall 20' long, but leave it free at both ends, and it reads 200 S.F. It looks to me like the wall area is always reading the center line wall regardless of what the Location Line of the wall is set to. As you can imagine this is problematic, especially if it were a 5' long wall on the exterior, the area drops from 50 S.F. to 40 S.F., a 20% reduction.

I understand that Revit doesn't really know which side of the wall you would want when reporting this information to you so it is probably playing it safe and going with the center line. Beyond this current % of opening issue I worry about any material takeoff information that might be drawn from this info. I checked the wall material take off schedule and it has the same problem. So I really think there should be some way to get this information for the model

I can't even use the Length of the wall reported in the schedule because it reports the centerline to centerline length of the wall. I did notice that you could Edit Wall Joins and affect the areas, but if you can get one reported correctly the other is off by twice as much.

Has anybody figured out a way to get the area for the actual faces of walls within Revit beyond manually multiplying the length shown on dimensions by the height of the wall? Any horrible hacks or fuzzy math out there for this situation?

[cliff collins]

I searched the forums, but did not find a good, concise answer for this.

You make a very good point. When you have two 90 degree walls, each wall has a different area on the Exterior face than it's Interior face--the difference being the thickness of the walls. So--I suppose Revit is reporting the "average"area--to the centerline? Shouldn't the area include both exterior and interior faces? And what about the top and bottom faces? Of course that would be included in the Volume, but that is not what we want here. How does Revit "know" which side of the wall it is reporting the area of?

I tried a quick test, mitering the walls in plan, and set the location line to finish face-exterior.This did not change the area in wall properties. I believe Revit sets the area as a read-only value, calculated to the wall centerline.

So--how to schedule areas for Exterior and Interior faces? Maybe we need Area Plans,
for Wall Elevations--which can be set to Exterior or Interior faces--like the Area Plans
tools for Plan Views?

Anyone have any experience here or ideas? Are we missing something?

Cheers.....

[dlpdi5b]

I use takeoffs of the individual wall materials to determine my wall areas. Revit kind of hides it, but is has good material takeoff tools. Go to View menu; New; Material Takeoff. This allows you to create a schedule of all the individual components that make up a wall.

[Mike Sealander]

I just checked out material takeoffs. They seem to work. That solves a big problem.

[Devin_82]

I just checked out material takeoffs. They seem to work. That solves a big problem.

When I do a simple material takeoff it isn't working correctly for me. I may be doing it wrong, but it seems pretty straight forward.

I have attached a PDF showing what I am refering to.

[jeffh]

If you edit the wall joins to use a "miter" instead of "butt" joint the face material should come out to the correct value (400 s.f.).

[cliff collins]

Jeff,

Thinking the same thing, I tried mitering wall joins and mentioned it in my post above--but it did not affect/or produce the correct area. Can you post your example?

cheers.....

[Devin_82]

"miter" instead of "butt" joint

I thought I was missing something... Thank you for pointing it out. Is there away to set all walls to "miter" instead of "butt" by default? If I had to manually go to each wall join in my building and change it I would probably go insane...

[jeffh]

Jeff,

Thinking the same thing, I tried mitering wall joins and mentioned it in my post above--but it did not affect/or produce the correct area. Can you post your example?

cheers.....


Here are 2 screen shots of the simple example. 20' cube.

I don't know of a way to set the walls joins to default "miter".

[cliff collins]

Thanks, Jeff.

We are able to produce the same results on the basic example.

Another question which has come up is: (see my orig. post above)

How to accurately do independent take-offs of the INTERIOR and EXTERIOR faces
of walls which are joined?

Let's say--a 20 story hotel--with granite exterior walls, $60 / sf
with marble interior walls, $100 / sf

The seemingly small discrepancy from the areas Revit reports VS actual interior and exterior areas will add up very quickly--more than a typical contingency factor allows?

Perhaps plug-ins like Vico Office or Building Explorer software have extra tools to make these distinctions for accurate take-offs?

cheers.....

[jeffh]

How to accurately do independent take-offs of the INTERIOR and EXTERIOR faces
of walls which are joined?

On the simple example with mitered joins I was getting accurate results for exterior and interior faces.


Let's say--a 20 story hotel--with granite exterior walls, $60 / sf
with marble interior walls, $100 / sf

The seemingly small discrepancy from the areas Revit reports VS actual interior and exterior areas will add up very quickly--more than a typical contingency factor allows?

This is a different situation totally. There is probably no way you will be able to get all of the joins in the walls in this example to work out perfectly. I suppose the question in my mind is, "How are the estimaters doing it now, without a Revit model? How close are they coming?" Is Revit dead on accurate, no. Can it be used as a tool to help in the estimating process? Of course. Estimating to me always has seemed a bit like a "black art" of sorts. I was never really good at it. :Oops: Even if Revit could throw out an exact number, it would not be completly accurate because of construction methods, waste, damaged products, etc...


Perhaps plug-ins like Vico Office or Building Explorer software have extra tools to make these distinctions for accurate take-offs?

I don't know. I have not used these products but it might be something to investigate and add to your "design weapons".

[cliff collins]

Jeff,

Thanks for the reply.
Part of the problem is that "the Estimators" are asking for our Revit model!!
We are starting to delve into IPD (Integrated Project Delivery) where BIM is the centerpiece for team collaboration. We are BIM enthusiasts and pride ourselves on being BIM-savvy, so we need to be able to back up our claims of "less waste", "NO RFI's",
"constant cost monitoring", etc.

The AIA has recently introduced new Contracts for IPD and BIM. If we are heading into
a new frontier such as this, and the BIM tool is being used by the Estimators to monitor cost throughout the design process--we need to be able to get accurate takeoffs from the Revit model.

Also--we (the design team) are also sometimes wearing the Estimator hat--and again
we need accurate take-offs. I'm quite sure we are not the only architects facing these problems.

I know that Autodesk has recently teamed up with Vico in developing their Vico Office
software--a "BIM nuetral" platform which uses the BIM data to examine 3D, 4D and 5D
aspects of the project. We are currently looking at this as a possible tool for use in BIM/IPD projects.

cheers....