Corridor Cost

A corridor uses floor area, structure, finishes and lighting while serving movement rather than direct occupancy. That makes its size and layout part of the project’s efficiency, but calling it pure waste misses what circulation does for access, safety and the experience of moving through a building.

Corridor Cost

Home 24 ft wide · core 24 ft × unit depth · stair 8 × 14 ft

Illustrative single floor, same homes in both plans. Each home is 24 ft wide and as deep as the unit depth, so net rentable area is homes × 24 × depth in both. The core is two stairs, two elevators and a lobby in one home-sized bay (24 ft × unit depth). A long bar would add an end stair in practice, which this leaves out. In the bar the core takes a bay in one row and the corridor runs the full length. In the point block each home needs 10 ft of frontage for its door and the stairs and lobby take 44 ft of the core's faces; when the faces run out, a hall ring (at most the corridor width) wraps the core, then stretches into legs. A second core is not drawn; its efficiency is computed as two point blocks of half the homes. Rent is an editable annual rate on every lost square foot. This does not establish code-compliant corridor width, travel distance or unit layouts.

Different layouts distribute that area differently. A double-loaded corridor places rooms on both sides of a hall; a single-loaded corridor gives rooms access to one side and more exterior edge. Cores, stairs, elevators and required clearances further shape the plan.

The study draws one floor twice: as a double-loaded bar, and as a point block, a compact tower with homes wrapped around a central core. Both plans hold the same number of homes and the same rentable area. Each home is 24 ft wide and 30 ft deep, 720 ft². The core is two stairs, two elevators and a lobby in one home-sized bay. Rent starts at an assumed $36 per ft² a year. These are assumptions for comparison. They do not establish code-compliant corridor widths, travel distances or unit layouts.

A long double-loaded bar with 10 homes runs a 6 ft corridor for 144 ft. That corridor is 864 ft², 86 ft² per home. With the 720 ft² core, the floor gives up 1,584 ft² and is 82% rentable. At the assumed rent, $57,024 of rent a year goes unearned.

Widen the corridor to nine feet and the same 10 homes lose 1,296 ft² to it, 130 ft² per home. The floor is 78.1% rentable and $72,576 of rent a year goes unearned. The three extra feet cost $15,552 a year on one floor.

A point block with 4 homes a floor has no corridor. Every door opens on the core lobby. It is 80% rentable and loses only the 720 ft² core, $25,920 a year. The bar holding the same 4 homes is 71.4% rentable, with 432 ft² of corridor and $41,472 a year unearned.

At 6 homes a floor the faces of the core still carry every door. The point block is 85.7% rentable with no hall. The bar needs 576 ft² of corridor and is 76.9% rentable, a gap of $20,736 a year on one floor.

At 8 homes a floor the faces of the core run out of door frontage, and a 3.5 ft hall wraps the core. It is 427 ft², 53 ft² per home, still less than the 720 ft² the bar spends. The point block is 83.4% rentable and the bar 80%.

Past about 8 homes the point block stops working. At 14 homes on one core, the hall stretches 13 ft out from the core to reach every door and grows to 1,296 ft², 93 ft² per home. The point block is 83.3% rentable. The bar, at 84.3%, now does better. A second core would give 81.5% and add another 720 ft² of core. The limit of 8 follows from an assumption: each home needs 10 ft of hall or core frontage for its door.

The design task is to make circulation legible and proportionate to the building’s use. Net-to-gross area can help compare options, but it does not measure whether a plan works well. Efficiency targets need to be checked against egress, accessibility, daylight, privacy and the project’s operational needs. A plan that saves area by making routes difficult has traded one kind of efficiency for another.