Providing Engineering Estimates

[weh3]

Does anyone use a rule of thumb on estimating engineering or design man-hours?

What about estimating time or cost per sheet?

What is a reasonable ratio of engineering and design costs to construction costs?

What about the ratio of engineering costs to design costs?

I got good at doing construction cost estimates on a previous job, but now, having to do engineering and design cost estimates, I am a fish out of water.

I know that it depends, etc., etc., but any help, O Tim, would be...um, helpful.

William

 

[cvg]

It really does depend, but can be estimated successfully if you have

a) A complete, detailed scope of work
b) A good understanding of what the client wants (not what you think they want or need)
c) Net profit should be directly related to the amount of risk you will undertake

Cost per sheet really depends on what you are drafting or ratio of design to construction is very inaccurate, unless you have data on many previous projects that are identical to this one... etc.

One good way to do it is to hold a scoping meeting with your client. You should start with a good scope of work. You will estimate and agree on the manhours / scope for each task in this meeting, and can't leave until finished and agreed upon. For larger projects, this has taken up to 3 days. Then go back to the office and calculate the $ based upon the agreed upon manhours and scope.

 

[DRC1]

I agree with cvg that the better defined the work, the better the estimate. Unfortuantely, on some projects, it is hard to get a good idea of how much work willl be required until you start the engineering. For estimates that require design engineering costs as well as construction costs with limited scope definition, I have used 5 to 15% of the construction cost. If engineering inspection is required, I will estimate the number of on site inspection hours at a typical rate, then add 25% for review and typing. These are for budget numbers.

 

[cvg]

DRC1

5 - 15% may be appropriate for civil or public works design, and you have the experience to know it works for you. However, we do a lot of work on small dams and the design can be as much as 30 - 40% of the construction cost. Design analysis and obtaining agency approval for dam construction is quite extensive, compared to the construction cost. The risk to the owner and designer is also higher and therefor demands a higher fee. I don't know what a good ratio would be for electrical design as weh3 is apparently doing.