Increasing occupancy on the floor of a building requires filing an alteration type 1 application with the DOB and getting a new (or amended) certificate of occupancy. An architect will determine the nature and extent of construction required to increase the occupancy.

A floor’s egress capacity will dictate the maximum occupancy load. Table 6-1 of the 1968 Building Code displays the correlation between stairs and capacity. The Building Code stipulates that stairs must be a minimum 44 inches in width to qualify as egress stairs. Table 6-1 breaks down the occupancy groups and their corresponding maximum occupancy load per set of stairs. For instance, occupancy group E (business/offices) permits 60 persons per stair unit. Since two units constitutes one set of stairs, one set of 44 inch stairs allows a maximum occupancy load of 120 persons on the respective floor. Considering offices are required to have a second means of egress for safety purposes, offices usually are able to achieve a declared occupancy load of 240 on their certificate of occupancy.

Offices permit 60 persons per unit, or 120 persons per stairs.

There are other requirements that have to be considered when increasing occupancy. Adding to the occupancy load may mean adding a bathroom if the New York City Plumbing Code requires it. Table 403.1 of the New York City Plumbing Code outlines the number of bathrooms required per occupancy load. Even if the occupancy load is drastically increased, the DOB will have to approve a floor plan that takes into consideration handicap accessibility.

It’s possible the declared occupancy on the certificate of occupancy is not the maximum permitted by table 6-1. In some cases occupancy is simply a chair count made by a tenant. Older certificates of occupancy are prone to this. This means that it’s possible the occupancy could be increased without any actual construction.

Whether construction is performed or not, an alteration 1 job application will have to be filed, inspections will have to be made, and a new TCO will have to be obtained with the new occupancy load.

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