Freeware? I don't think so. You can however get an estimate by using Means Construction Cost Data. Of course you must know what material is going into the structure and a little about the construction process.
I use a compilation of costs from several projects in the form of an excel spreadsheet.
If a client requires an estimate, I just delete the items not included and fill in the quantities for those that are required. It's pretty simple and yields fairly good results - generally within about 10%. Because it is a compilation of current data, it should be close, only thing is that depending on the labour force available, there is a little 'fudging' of values... but, with the positive and negative errors, it comes pretty close. For items not included in the spreadsheet, we use the Means or Dodge costing books.
Also occasionally prepare three or four estimates, depending on the degree of precision required. They are Class A to Class D with Class D being the most precise.
If you want, I can send you a copy of the latest one done; it's for a parking lot with a handicap access ramp. Only problem is that our costs likely differ significantly from yours and the items included in the spreadsheet will be different; but you will be able to use it as a bit of a template.
I also do 'post-mortems' on project costing and obtain costs from the successful contractor; this helps keep a current set of unit prices.
It's a simplistic way of doing it... but seems to work OK.
