In Safdie's earliest designs for Habitat '67, the building was to be constructed out of rhomboid-shaped modules, a form which gave way in subsequent drawings to the simpler geometry of rectangular boxes. Each module measures 12 m x 5.33 m x 3 m, or 56 m2 (38 ½ ft long x 17 ½ ft wide x 10 ft high, totalling 600 ft2), and weighs as much as 90 tons. Habitat's modules were all constructed and assembled in situ: an on-site factory was used to produce concrete which was then applied to the prefabricated steel cages that were to become Habitat's signature modules. The modules were then lifted into place on the main structure by crane, and arranged in one of 16 different configurations. The concrete exteriors were sandblasted, and no further surface treatment was added.

For both Habitat New York schemes, modules were to be octagonal in plan and cast in 'prestressed' or lightweight concrete at a local factory and shipped along the East River to the Habitat site. In the case of Habitat New York II, two separate octagonal modules were to be realized (each differing in size and shape), and combined to produce numerous configurations for single- or multi-level dwellings. For this second scheme, each unit's plumbing and electrical elements were to have been supplied directly through the modules, before being routed back to a central structural core at the complex's base.

The basic shape of the modules designed for Habitat Puerto Rico was a split-level hexagon. The geometry of the hexagon would have provided shade to underlying residences by virtue of the way units were to be stacked and cantilevered atop one another. Once prefabricated at a central manufacturing plant, these light-weight, concrete units were to be transported via truck or barge to their intended site. It was thus shipping requirements which dictated that the width of the modules not exceed 3.6 m (12 ft) so as not to hinder their transportation on the island's highways.

Unlike earlier Habitat projects which featured self-contained units with no projecting volumes, the modules for Habitat Israel were conceived in two essential parts: the box and the dome. The semi-circular, mechanized fibreglass dome that Safdie devised specifically for this project was to be fitted into a track located at approximately two-thirds the length of the module's principal concrete box (measuring 11.6 m x 3.6 m [38 ft x 12 ft]). This rotating dome would have allowed each resident to control the exposure of sunlight entering their residence. There were also subcomponents designed to be added to the module, depending on the site's specific requirements. The Ministry of Housing had conceived of placing various manufacturing plants throughout the country to produce these prefabricated modules.

Like the original Habitat in Montreal, individual modules for Habitat Rochester were designed as concrete, rectangular boxes, measuring 3.6 m x 10.9 m (12 ft x 36 ft). Units were composed of two overlapping modules arranged at right angles to one another, creating two-storey residences with slanting roofs for added volume and height. Each residence was also to have featured a 3.6 m x 3.6 m (12 ft x 12 ft) garden terrace, convertible for indoor winter use and accessible by sliding glass doors. Residences were to have ranged from one-bedroom units measuring 56.2 m2 (605 ft2), to three-bedroom units measuring 90.6 m2 (975 ft2).

As construction techniques and structural issues were never finalized for this project throughout its two-year life span, the decision to use a fully industrialized box system (whereby the modules would be prefabricated and cast on site as opposed to being built according to conventional construction methods), remained unresolved. Nevertheless, modules were to be variations on Safdie's signature 'boxes,' most of which would be configured into two-storey dwellings oriented around a two-level atrium. Residences were to vary in size from two-, three-, and four-bedroom units, and in area, from 112 m2 to 224 m2 (1206 to 2411 ft2). Habitat Tehran is the only Habitat design not to feature one-bedroom dwellings, which were felt to be unnecessary in a family-oriented complex.