Estimating Modelling Time?

[barrie.sharp]

I am struggling to give good estimates as to how long a model will take in Revit. Sometimes a model flies together and at other times I'm scratching my head to get things to work. I have to draw alot of refurbs so I model existing buildings and I have to keep true to the original which somethings makes modeling complicated.

Revit is unforgiving with existing plans because it's honest. Did anyone have to change the way measured surveys were done to get them into Revit? People use to make 2D CAD just work. I find that I look at a building and can't make a good guess at time required anymore. I think it's the surveys that are slowing things up because I need to know so much more now, especially when setting levels. It's adding pressure to time constraints.

Anyone have experience with this?

[iankids]

Hi Barrie,

I have found that I have needed to change the way I allot time to any given project. In AutoCad, I could throw together some quick floor plans knowing I could fix up the minor stuff latter in the design phase and thus would allot only a relatively small amount of time to the preliminary stage.

With Revit, I find that this process is totally reversed. I MUST set sizable amount of time to set everything up well at the very beginning. Revit has bitten me, and bitten me hard, if I have taken any shortcuts in the set up preliminary phase.

The big benifit of course is in the middle and latter phases of any design when everything simply flies as the early stuff was done correctly in the first instance.

With regard to the surveyors plans, most of the time I use them as a guide only. As there has never been one house which I have worked on which is perfectly square, plumb and level, unless there was a meaningful error, I will model the house as if it was square, plumb and level. I would pay particular care to ensure that the bit of the house where the builder is to be connecting the new works was modelled pretty accurately, but if the was a 15mm out of square between this element and the other end of the house, as it has no bearing on the design or the builders ability to construct the extension, I would simply ignore it.

As the vast majority of my work is extensions and renovations, I am very careful in setting up the existing conditions as accurately as I can (within the above constraints). Once I am happy with the existing conditions I pin everything down and only unpin those elements I need to demolish or alter. From then on in, it is plain sailing from a model perspective, one still has to deal with the clients whims, come up with a grand design and keep it under budget of course, but at least I know that I won't get bitten by poor early work.

Ian

[barrie.sharp]

Hi Ian,

Thanks for that reply. It clarifies my position alot. I wasn't so much concerned with the proprty being square etc. The Revit mantra is to model it as it's built! With existing buildings, it would be invasive to actually suss out how it went together. In the spirit of approximation I guess but I need extra info to pull it of such as:-

every wall thickness
reveals
all head heights for openings, ceilings etc...
floor levels, thickness etc..In other words, a 3D survey rather than flat.

I relate entirely to the idea that you can just knock it together in AutoCAD and being flat, not worry about how it's put together. Have you had to make sure that the measured surveys are more thorough or were they pretty comprehensice to start with?

Where we have existing walls, I have started using generic wall types with just thicknesses set and only set up wall compostion on new componants.

[twiceroadsfool]

Hi Ian,

Thanks for that reply. It clarifies my position alot. I wasn't so much concerned with the proprty being square etc. The Revit mantra is to model it as it's built! With existing buildings, it would be invasive to actually suss out how it went together. In the spirit of approximation I guess but I need extra info to pull it of such as:-

every wall thickness
reveals
all head heights for openings, ceilings etc...
floor levels, thickness etc..In other words, a 3D survey rather than flat.

I relate entirely to the idea that you can just knock it together in AutoCAD and being flat, not worry about how it's put together. Have you had to make sure that the measured surveys are more thorough or were they pretty comprehensice to start with?

Where we have existing walls, I have started using generic wall types with just thicknesses set and only set up wall compostion on new componants.

CAD was unforgiving too, if you went all the way around an existing building in Plan, and WANTED the dimensions to "close."

Estimating time in Revit isnt too bad, and youll get the hang of it... A lof of it is looking at something you have to model and knowing where the hangups are going to be. But a bigger part of it is avoiding the tunnel vision of "Because im modeling it, it HAS to be perfect..."

Im reality, you dont need anymore information than you did in AutoCAD... Youll just get the same result. Dont have opening head heights? No biggie, put in an opening with a height you guess at, and mark it or denote that its not VIF. Same with wall thicknesses. Our template has 4 walls. Generic Ext, Generic Int, and two rated walls. If you DONT know the wall thickness, you use those.

In concept design, the project isnt going to wait and get tied up while we field verify every nook and cranny, so just like autocad we make what we need, and we verify it as we progress.

i *DO* agree that before PRODUCTION work happens, that the entire *existing conditions* be modeled ACCURATELY (IE started over, if the concept model was hacked together as i described above), but i used to do that in ACAD too. Many times starting fresh is much faster and easier than starting with hacked design items...

[barrie.sharp]

..."Because im modeling it, it HAS to be perfect..."

...i *DO* agree that before PRODUCTION work happens, that the entire *existing conditions* be modeled ACCURATELY...
You have a good point and perhaps I do get too hung up on accuracy but you do add more precision later by the sounds of it. I was hoping to get schedules out of Revit for bill of estimates but it's more complicated than it sounds with one of the issues being model accuracy. You're right about AutoCAD not closing and I guess I forgot about it's shortcomings because they're so different from the issues I now have in Revit.

So the question I'm left with is when to model accurately. I will have to learn where the hangups are. I suppose that I'm still early days and the learning curve is only just starting to level out. When I started Revit everything was a hangup!