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BIM makes all these schedules but how do you get from the material takeoff in the schedules to a cost estimate? For example, what do you need to make a cost estimate at the start of DD? Architects have to make cost estimates, often before there is a contractor on board. I'm at a stage in the beginning of DD and the project will go out to bid eventually but there is no contractor to get the price yet. Or, even earlier, in massing model phase where you only have the volume to go by, how do you get pricing from a BIM?
You don't get pricing from BIM. You get quantities. If you did a good job building your model.
And, it's your job as an architect to turn quantities into $. How about early on doing $/PSF?
If you're an American architect, be VERY careful about giving cost-related information to your clients. That can have serious blowback under our legal system. Note that this is the exact opposite of how it is in many countries, where architects are legally responsible for providing quantity surveying at various stages of design.
"Opinion of probable cost"
i mean i guess you could look up RS-Means numbers and attach them to the quantities, but estimating is a lot more complicated than that. That's why "senior estimator" is a generally well-compensated position. You really need to know everything, down to how much dimensional lumber you would need to frame a concrete form, etc.
gwharton: can you expand on that for the benefit of the younger folks on here? I work on mostly international projects and our consultants provide detailed cost estimates for our clients all the time, so I really have no knowledge in this area and am now quite curious. I suppose that it could be quite dangerous legally in the US to say that a specific part of a building will cost X and then be caught totally liable for the extra cost when it ends up being X+Y but is it different/more than that?
We do per square meter costs to start then get rough estimate when prelim design is advanced enough. For bigger projects we do our own estimates same as contractor does. Then bid out competitively. Still get surprised which is a bitch. No legal ramifications here though. Am also curious what you work to in USA if budget talks are verboten. How does that work practically ?
We do "opinions of probable cost" and tell the clients that we are probably within 10-30% and the only real estimate comes from the contractor when the project is bid & that the market is rising etc. works ok, except when you are actually 30% off...*price face palm*
Ps, read the AIA contracts. Arch is not liable for costs.
architects do not do detailed cost estimates.
If you have to ask, you can't afford it.
If the client gives an architect a budget they have to stay on budget or redesign the building or parts of the building to meet the budget. That is fair and the architect does not have to agree to the number if it is unrealistic. I could do a cost per sq ft estimate based on previous jobs. However, I'm not doing the same project over and over. When an architect wants to make something interesting and venture into new territory it makes BIM look useful. The question is how useful is it and how does it relate to qty.
we do detailed estimates on a regular basis. our public schools contracts require it. for others it's an important tracking tool.
your estimate is as good as your knowledge of the market. we get help from contractors sometimes, but usually rely on our experience, vendors, rs means, educated guesses...
if you're clear with your client about what you've done, it's not that dangerous. a little wrong is reasonable. we've been very wrong, of course, on occasion, but the repercussion is usually just some rework for which we'd take responsibility anyway, just to keep our client happy.
BIM is only useful if the person drawing is entering the information knowledgeably and intentionally toward using it for estimating, ie, not just for the drawings. otherwise the output can be a bunch of useless garbage.
++Steven my experience exactly
ah ok that is how it is for us too steven. we also don't take responsibility for costs and warn clients in advance that we are not builders and by the way the market is changing. 30% sounds way out of touch, but I like the idea of making the range that high.
things are getting expensive here funny enough. first time to see a real jump in costs in about a decade. abe-nomics. totally messing with our experience about what things should cost. its a real bugger.