Today, Mayor Bloomberg will sign into law the first major revision of the city’s building code in nearly 40 years when he affixes his John Hancock to legislation overhauling the administrative and plumbing sections of the mammoth regulation. Some elements of the new code represent significant progress, while problems remain. The way the revisions have been rolled out raises the possibility that the update could still be derailed. Nonetheless, the mayor and his buildings commissioner, Patricia Lancaster, deserve credit on this part of what is a larger reform drive.

The city’s first building code was enacted in 1850 and has undergone two major revisions since then, the most recent in 1968. It has also suffered serial tinkering throughout its lifespan, which has created an internally inconsistent behemoth stretching longer than 700 pages. The difficulty of interpreting the code and navigating the labyrinth it spawns has spurred a cottage industry of “expeditors” who help developers wade through the text and, as the Manhattan Institute’s Julia Vitullo-Martin has noted, also create a corruption risk.

The current code requires that materials used in construction projects here receive special safety certifications required by no other jurisdiction in the country. Right now it prohibits the use of plastic PVC piping in any building much taller than a Brooklyn brownstone, for example, and the list of cost-raising esoterica goes on and on. The code helps explain why construction is so expensive; by one count, the average hard cost per square foot for a high rise in New York City is $154, which is 36% higher than the $113 national average. In Chicago, the hard cost of a square foot is $125.

The logical solution is to adopt a “model” code, such as the International Building Code in use in more than 40 states and Canada. In 2002, Mr. Bloomberg started a drive to bring such a model code to New York. The administrative and plumbing sections being signed today are the first legislative fruits of that effort. The number of special interests with stakes in the status quo has always bedeviled efforts to rationalize the code. It’s significant that the first round of revision affects the plumbing code; plumbers have traditionally been among the most change-averse.

Some of the most infamous restrictions and requirements have found their way into the new code. For example, New Yorkers will still face a requirement that they employ plumbing firms that are majority-owned by master plumbers within the city, a provision that reduces competition and raises prices. Old restrictions on the use of plastic piping remain: Under the new code, PVC piping can only be used in residential buildings up to five stories tall, as opposed to two stories under the old rule. Plumbers favor the prohibition on this cheaper material because it is less labor-intensive to install so it threatens their job security. Although the process has been streamlined, manufacturers will still need to receive special certification from the city before their innovative new products can be used in construction projects.

The proposal signed today will not take effect until early 2007 and even then is conditioned on the enactment by the City Council next year of additional new sections dealing with the “meat” of the building code. So New Yorkers are unlikely to see immediate improvements in construction costs. Yet Mr. Bloomberg and Commissioner Lancaster have at least started toward building a more sensible code.