BIM and too much detail

[KeesW]

We do a lot of small and medium sized work and have too many drawings for each project. I wonder if the use of BIM causes this because everything has to be resolved to produce a good model. Then, if it is resolved, one might as well include it in the documentation. This leaves too little to the contractor's discretion, and the amount of detail provided makes him think that the works are more complicated than they are. This increases the cost.

An independent technician working from our office, using Microstation as a 2D drafting tool, produces full working drawings for small projects such as houses in a few days. Of course, things are not as well resolved but information is more than adequate for contruction purposes, and the quotes he gets from contractors are much lower than ours for similar sized projects.

I understand that resolution of every miniscule item might be necessary for large developer driven projects where profit and avoidance of liabilty are the main considerations. However, for small and medium jobs ........?

Any opinions on this?

[Eduardo Rolon]

The following is a generalization,

1. A lower Bidding cost due to lack of information will usually result in more change orders and greater cost during construction.

2. A higher cost during bidding due to more complete information in the construction drawings results in less change orders and maintaining the bid cost.

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In scenario 1 the contractor lowballs it because he knows he can make up the profit during construction when it is more difficult or impossible to change contractors or stop the project.

If you want to lower the cost of #2 meet with the contractor after bidding to see were you can lower costs before construction starts.

You are assuming that the bidding price is the final construction price. It is better to compare the percentage of change orders between the projects and check the final cost of the building, as a percentage you want this to be as low as possible and you might be surprised. In scenario #1 you might want to also check the amount of documentation produced during construction to fill in what was not designed and drawn during the preparation of the construction documents. IMO it is more attractive to clients to be able to demonstrate that your estimates and the final cost of construction is within a reasonable number ±5%.

The other error is that you are assuming that the contractor is quoting higher because he thinks the project is more complicated might it not be possible that he is quoting higher because he has all the information he needs?

BTW this is not a BIM vs 2D issue, we used to have this argument at the office I worked pre-computers also.

[Anonymous]

The question of how far to go when documenting is a tough one.

Ideally we would have enough scope to resolve everything on 'the drawing board', but in reality this rarely happens.The comment 'the devil lies in the detail' is a very true one.

Also the surprises that come up during construction are not always negative ones. The process of building and working together with a contractor can be synergistic.

I suppose it comes down to appropriately pricing a job at the start so that you allow enough fee to provide adequate documentation to get the project out of the ground, but also making your client fully aware that they require your services during construction to make sure the intention of your design is carried out by the contractor.

For smaller projects, once again, I find it really important to communicate a 'this for that' arrangement. For example, you will get plans that will get you to a certain stage eg: achieving council approvals and then give a clear indication of what else you can provide subsequently and what your fee/hourly rates will be for these additional services.

Regardless of whether you are in BIM or 2d, a coherent set of drawings is an asset to your client.

[KeesW]

Thanks for your comments so far. I've been in private practice a long time and understand what you are saying. The point that I was making about using software such as Archicad that relies on creating accurate 3D models from which to generate plans, elevations and sections, is that the information and detail created may be much more than necessary for either approvals or tenders. I suppose that one alternative is to model walls, floors and roofs and perhaps ceilings and then to use the 2D Detail tool and Worksheets, to create the other stuff.

The problem is (in my case at least) the user - it is both fun and satisfing to build a detailed 3D model and hard not to use the information created in the final documentation. Maybe the answer is more self-discipline!

[Anonymous]

Cornelis,
another way to take advantage of this excess of accuracy without getting an increased quotation from the contractors, if ever self discipline does not work, would simply be not to provide all the material you have done. What if you were still doing the same amount of work, but were keeping a part of the details, providing only the usual necessary set? You could keep this excess of information for later stages, staying ahead ready to provide more. It could be a kind of freedom you keep for the benefit of your office.

[Anonymous]

I would agree with all the comments so far, and add that a sophisticated contractor who understands his own process and needs when pricing, in combination with greater 'self-discipline' or simply a more thoughtful approach to modelling may be a better way forward for you.

It sounds like you are in residential design? Most building methods in residential design is not rocket science, and helps to expedite drawing production cycles, in my opinion. On the other hand, what I have found is in producing the quality of documentation that Archicad is capable of, will set you head and shoulders above most of your competition, bringing in bigger budget jobs hopefully, and allowing you to charge full dollar for your services and expertise.

Just my two cents.

[Anonymous]

Kees,
I agree with Til, the level of detail shown is your choice. I keep a layer for sections that I want to see but will probably never show anyone.

As far as too much detail on small jobs, what about working with plain jane elements, de-BIM it a little, i.e. no composites (or very simple ones) for walls, slabs nor roofs. Then your sections can add back in any detail level you want. And you still get all the error checking inherent in having built a good model. After all, the Microstation guy you mention, probably is drawing a wall with just two lines for the plan, or maybe a third line for brick veneer etc.

I have to say though, regardless of presentation or documentation requirements, a good model helps me sleep at night. Plus, as you mention, it's fun.

Snap

[Arcadia]

In my experience it is better to come down slightly more towards the too much detail than the too little as I think if builders can see exactly how 'everything goes together' I think they are less likely to add in contigency amounts into their prices. Maybe this is not always the case. I do know that a lot of tradepeople are nowhere near as good at reading plans (or following them) as they should be so maybe some of them are scared by detailed plans but if you provide extra detail and there is a porblem on site because they haven't followed plans correctly at least they can't complain to you. If there is not enough detail the trades can blame the designer. I resolve the detail issue by having an extensive library of standard/generic details which have been drawn in 2D which I just put into my layouts as needed. So a typical basic dwelling would only have 1 standard low detail 1:50section plus maybe 2 pages of standard 1:10 details which take no time at all to put into the plans.

[Arcadia]

And your detailing should follow the generally accepted local construction methods so that they are readily recognizable to any trades (unless the job is a unique job in which case you will need unique detail anyway).

[Anonymous]

The "amount of detail" discussion applies to office workflow, as well. When I started with AC I was worried that on simple building types I'd spend a lot of extra hours getting the model exactly right, detailing things that would be glossed over if done with 2d drawings. I'm still new to AC, but at this point it looks like the extra hours spent on the model are more than made up by a combination of getting a lot of sections and plans quickly, and all the reference tags automatically updating as I move stuff around.

And this doesn't even account for all the headaches and embarrassment saved when I've missed a few incorrect detail tags during drawing coordination review.