Anyone know of a good resource on how to estimate remodeling costs?

My wife and I are considering remodeling our home in Minnesota.  In the plans are to add a new story, enclose with glass and heat a current covered outdoor patio.  We've been working with an architect and just got a rough estimate on what this "small" remodel would roughly cost.  When the builder said, "$372,000" my jaw hit the floor.  He did seem honest and like he know what he was talking about but I just can't believe it would cost that much.  So...I'm trying to roughly calculate the material costs for the project to see if his numbers add up.  Calculating the number of 2x4s needed, costs of windows, plywood, ... isn't too bad as I can figure that out.  I'm just not familiar with what the others costs (electrical, heating, insulation, trusses, ...) are.  Can anyone shed some light on this?  I'd love a spreadsheet where I can calculate the costs room by room instead of rolling all up into one figure.  This would allow me to compare the estimated costs to he contractor costs and see if they are even close.  I'm just looking to get close, not exact.

Thanks.

Darren

I think your methodology for trying to analyze the cost is flawed.  Is your architect experienced in desiging and overseeing remodeling projects?  Did you give him a budget?  The answer to both of these should be yes, and if not, why not?  Your architect is who you should be discussing the cost with and why they are so high or recommending a contractor they have worked with in the past.  I have known people who found a good contractor first and have that GC in on the planning with the architect from the beginning and they ended up with a design that worked for their budget because the contractor is usually better able to advise the architect as to what the costs are likely to be.

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