Costs per square foot: remodeling is different

Q. Is there a rough way to calculate square-foot costs for remodeling a house? How will we know if an estimate is out of line? We want to add a 56 -square-foot, second-story bathroom over an existing one. In the first estimate , the square-foot figure is twice what it is going to cost the town to remodel its Victorian library. The new bath, in fact, will cost about one-third of what it cost to build the entire house only 10 years ago. Why? Is the bathroom one of the most expensive rooms to build? Ann Hattes Danvers, Mass.

A. Yes, bathrooms and kitchens are the most expensive rooms in a house to build or add. You have to remember that inflation has added between 10 and 15 percent a year to construction costs; therefore, I am not surprised at the present cost of your bathroom addition.

Romodeling costs are higher and harder to figure than new construction.

Bids for additions are also on the high side, since such jobs encounter unexpected costs from invisible conditions that invariably pop up.

Small jobs usually involve higher costs per square foot. This partly explains the high per-square-foot cost difference between your bathroom addition and the remodeling of the library. You can't really compare an apricot to a pumpkin.

Rough -- or even polished -- square-foot calculations on remodeling simply won't work. The right way to figure remodeling costs is to price out all materials and estimate the required labor. Less than that is unscientific guessing.

How does one know when an estimate is out of line? One way is through competitive bidding by two or three reputable contractors. However, such competitive bidding, to be fair, should be based on a throughly prepared set of plans and specifications, not merely on an oral description of the job.

For your small bathroom addition, I recommend you carefully choose a local experienced, honest builder. Work with him on planning and specifying the addition on paper. Then the builder can figure the cost of labor and material and review it with you.

At that time, you have the option to build or not to build.