It’s been my observation over the years that framers often quote prices for their projects based on the project’s Square Footage which I’ve always considered a bad idea due to the inherent lack of accuracy (see The Hidden Danger of Square Foot Estimating). Then when they try to move on to bid interior finishing projects the often meet with disastrous results. It’s not that ‘square foot’ estimating works for framing and just doesn’t work for interior finish because in reality it doesn’t work for either. It is perhaps just that the dire financial consequences are far greater using ‘square foot’ estimating on an interior finish bid than they are for framing.
The finish contractor would either lose their shirt pretty quickly or the better and smarter GCs would recognize that you were out of your league and didn’t know what you doing pricing-wise.
And likewise if the GC is looking for a SF price either they either don’t know what they are doing or they are looking for a finish contractor they can take advantage of because there is absolutely no correlation between the SF footprint of a house and the cost of architectural woodwork installation. Most trim work (although not all of it) is based on linear footage (i.e. baseboard crown etc.) or by the piece, assembly, or unit (such as doors) and when a ‘square foot’ unit cost does come into play it has nothing to do with the square footage of the structure and instead relates to the square footage of the material being installed.
Okay those warning and admonitions aside the key to estimating trim is producing an accurate project takeoff. Think about what you need to include in your estimate. Did the GC give you a scope of work document to tell you just what he or she was looking for you to do? Finish carpentry includes such items as:
- doors and door frame
- finish hardware installation
- cabinets and shelving
- milled trim
- non-milled but exposed to view trim
- wall paneling
- stairs and stair railings
And you need to takeoff and plan for fasteners, biscuits, dowels, glues, putty, bondo etc. even if they aren’t included on the plans and specifications you are looking at.
You need to know if the GC is expecting you to supply all those materials, some of them, or none of them? If you are supplying the materials (maybe not the best idea if this is your first “real” trim project when you’re working for an experienced established GC) then you need to get prices for the items in your takeoff from the various suppliers. Be sure that the time it takes you to perform the take-off and the the time it takes you to shop your materials list is included in your bid in one way or another (otherwise you are giving away your time for free).
You also need to keep in mind what the probable state of completion (fabrication) of the items upon their arrival at the jobsite. In other words are the doors pre-hung or will you be assembling jambs and installing the door in place? Are the cabinets finished and ready to install or are they knock-downs that need assembly on site. Same thing regarding the stairs. Are they site built, a knock-down kit, or are they coming fully assembled and all you have to do is install them. And what about the railings? I think stairs are easy and it’s the railings that are really difficult. Some items such as closets and bookshelves may come in part or pieces all ready to be installed or you may have to cut and fabricate them from materials on site.
Having considered all the materials you now need to look at the labor involved. You need to both think of a labor cost related to each and every associated item on your takeoff and also:
- Unloading of materials from trucks, handling and temporary storage and protection
- Special tools equipment and scaffolding
- Handling and hoisting materials from storage to final position. (generally applies to stairs but can apply to other things too such as safes or large cabinets)
- Incidental associated items of work such as backing in partitions for the securing of cabinets and trim.
- Who is going to prime or seal the trim before installation?
Arguably another good idea, especially on the intricately detailed jobs is to take off the number of cuts your crews will need to make to install and fit the trim. While you still need the linear footage of the trim to calculate just how much trim your cost of labor is more realistically ties to the number and difficulty of the cuts your crew needs to make (see Cost Driver 
and Cost Estimating Relationship for the technical terminology describing those relationships). Typically we price trim installation by the linear foot and add a ‘per cut’ cost modifier only when the particular project or room exceeds what we feel is a ‘typical installation’.
In some of the discussions I’ve been involved with online with neophyte interior finish contractors I’ve recommended that they go out an purchase a Craftsman Books – National Renovation & Insurance Repair Estimator and use the Man-Hour labor estimates that are in there as they apply for the kinds of work you’ll be performing times your Loaded Hourly Billing Rate. I recommend the NR&IRE book as opposed to some of the other ones out there for finish work in that that book has the widest range of finish items that I have seen.
I say to use the Man-Hour calculations rather than the labor costs that they have computed out because your Hourly Rate is unique and I think most every ones Hourly Rate is. They may average around a certain number in a certain range for a certain kind of work but we all have different schedules of overhead calculations and there are regional differences too.
You also might want to check out Jim Tolpin’s Finish Carpenter’s Manual. One of the real good things about the book is at the end of each chapter he gives some of his own man-hour figures for the task he has just described and there a good foundation to start from in building your own. Also check out the new edition of Gary Katz’s Finish Carpentry: Efficient Techniques for Custom Interiors, No man-hour figures in it but it’s full of great technique ideas. I now use both those books as training manuals for new hires.
There are certainly more subtleties involved in producing and interior finish carpentry estimate but this presents a good foundation to build on.
