How much per square foot?

Every year, a variety of construction-oriented periodicals publish the per-square-foot price of building a new home of a specific caliber in a specific region. With prices ranging from $200–$500 per square foot, it’s easy for the owners of existing homes to translate that equation to their own remodeling job and think, “Well, my bathroom is only 35 square feet so that means I should be able to remodel it for between $7,000 and $17,500.00!” In point-of-fact, per-square-foot pricing is not a relevant benchmark for remodeling because it does not take three very important factors into consideration;

Demolition and rubbish removal – not necessary in new construction – costs money. Before beginning the project, the existing space must be stripped of all the fittings, fixtures, sheetrock, insulation, flooring, etc. Those materials must then be removed from the home (taking care not to dirty or damage the walls and floors of adjacent, uninvolved rooms) and disposed of.
Tying in to old work is more labor-intensive than installing all new work. Imagine an electrician installing recessed lights in a house that is currently under construction – all of the joists are visible and wiring is simply stapled up in clean straight runs to the electrical panel which is completely accessible. Compare this to installing the same lights in a pre-existing, plastered ceiling – to place a light, a hole is cut in the plaster. If a joist is revealed, a new hole must be cut and the other hole patched over. Wires must be “fished” across closed ceilings and down sheetrocked walls to reach the electrical panel. This comparison holds true for almost every phase of a remodeling project from excavation to pouring a foundation to framing to flooring to painting.
In new construction, the “big-ticket” items like plumbing and electrical are averaged over the square footage of the entire house. The plumbing for a kitchen and two and a half bathrooms is very expensive but is averaged over 2500 square feet. When a home is being remodeled, that same work is often averaged over only a tenth of the square footage.