Unit types and layouts

In the second week, Castellanos fills the studio's long table with tape. She has marked out, at full size on the floor of the crit room, the outline of the Mwangi family's current apartment: two bedrooms, a living room with a kitchen along one wall, a bathroom, and a hall barely wide enough to pass in winter boots. Next to it she has taped a three-bedroom plan from a non-profit building she designed fifteen years ago, about 215 ft² larger. The students are asked to furnish both with cardboard furniture at full size and then to act out a weekday evening for a family of five: cooking, eating, homework, bath time, someone coming home late from a shift. In the old apartment they run out of space almost at once. The bunk bed blocks the window, the stroller has nowhere to go, and the dining table only fits if the sofa is pushed against the radiator. In the larger plan, everything fits, but Ingrid points out that the main bedroom door opens straight onto the living room, so the parents cannot sleep while the teenager watches television. 'Both lessons matter,' Castellanos says. 'Size first, then arrangement.'

The basic unit types

A dwelling unit is a self-contained home with its own entrance, kitchen and bathroom. In multi-unit housing, units are described mainly by the number of bedrooms and by how they are arranged in the building.

• Studio, or bachelor apartment: one main room for living and sleeping, with a kitchen along one side and a separate bathroom.
• One-bedroom: a living area with kitchen, a separate bedroom and a bathroom; often the home of a single person, a couple or an older resident.
• Two-bedroom: suits a small family, a couple with a guest room or home office, or two roommates; the most flexible type.
• Three-bedroom and larger: family homes, often with a second bathroom or a powder room.
• Townhouse: a unit of two or three stories with its own front door at ground level, attached to its neighbors on one or both sides.
• Two-level apartment, sometimes called a maisonette: a unit on two floors inside an apartment building, reached from a corridor on one floor.

Units are also described by their outlook. A single-aspect unit has windows on one side only. A dual-aspect or through unit has windows on two opposite sides, which allows cross-ventilation and daylight from both sides. A corner unit has windows on two adjacent sides. These distinctions matter greatly for daylight and ventilation, as lesson 6 will show.

Sizes that work

Building codes set only minimum room sizes, ceiling heights and window areas, and the minimums are small. Good practice sizes units from the furniture and activities they must hold, not from the code. Greenway Homes uses target unit sizes that it has refined over many buildings: about 430 ft² for a studio, 590 ft² for a one-bedroom, 810 ft² for a two-bedroom and 1,020 ft² for a three-bedroom home. These are net areas, measured to the inside of the unit's walls. They are generous compared with many market rental buildings of recent years, where one-bedroom units of 480 ft² are common, but modest compared with the houses most families have lived in.

The table below gives typical minimum furniture and clearances that the studio uses when testing unit plans. They come from standard design references and from Greenway Homes' design guide.

# Room-by-room area of a two-bedroom family unit, checked against the target size
rooms = {
    "entry and closets": 48,
    "living": 195,
    "kitchen and dining": 150,
    "main bedroom": 135,
    "second bedroom": 102,
    "bathroom": 54,
    "storage and laundry": 44,
}
rooms_total = sum(rooms.values())
walls = 0.10                  # partitions and internal circulation, as a share of the rooms
unit = rooms_total * (1 + walls)
target = 810
for name, a in rooms.items():
    print(f"{name:20s} {a:6.1f} sq ft")
print(f"Rooms total          {rooms_total:6.1f} sq ft")
print(f"Unit with walls      {unit:6.1f} sq ft  (target {target} sq ft)")
print("Within 5 of every 100 of the target" if abs(unit - target) <= 0.05 * target else "Revise the rooms")

entry and closets      48.0 sq ft
living                195.0 sq ft
kitchen and dining    150.0 sq ft
main bedroom          135.0 sq ft
second bedroom        102.0 sq ft
bathroom               54.0 sq ft
storage and laundry    44.0 sq ft
Rooms total           728.0 sq ft
Unit with walls       800.8 sq ft  (target 810 sq ft)
Within 5 of every 100 of the target

The room list shows where the area goes. Living, kitchen and dining together take about two-fifths of the unit, the two bedrooms about a third, and the bathroom, entry and storage the rest. The allowance for walls and the short internal hall is small because the plan avoids corridors inside the unit: the bedrooms open off a small lobby next to the living room rather than off a long hall.

Zoning within a unit

Even a small apartment has zones. The living zone, with the kitchen, dining and living spaces, is shared and active; it benefits from the best daylight and views. The sleeping zone, with the bedrooms, needs quiet and privacy. The service zone, with the bathroom, laundry and storage, needs plumbing and ventilation but not windows. A good plan keeps these zones distinct while connecting them efficiently.

• Place the entry so that visitors arrive in the living zone, not beside a bedroom door.
• Group bedrooms together, separated from the living zone by a door, a closet or a short lobby, so one person can sleep while another is awake.
• Put the bathroom close to the bedrooms but reachable from the living zone without passing through a bedroom.
• Put the kitchen where the cook can see the dining table and, in family units, the children's play area or the courtyard.
• Line up the kitchen and bathroom with those of the units above and below, and next to a shaft, so plumbing and ventilation stack vertically.

Castellanos is emphatic about the last point. Plumbing that stacks straight through the building is cheaper, leaks less, is easier to repair and allows a regular structure. Plumbing that shifts from floor to floor requires horizontal pipes in ceilings, which bring noise, cost and future leaks. Unit plans in a building are therefore designed in families that share a common service wall.

The entry sequence and storage

In a cold climate, the entry is one of the most important parts of a home. Residents arrive with boots full of snow, wet coats, strollers, groceries and bicycles. An entry should have room to stand inside the door with it closed, a bench or a place to sit and remove boots, a closet for coats, and a hard floor that can be mopped. Family units need space for a stroller and outdoor toys. Studios and one-bedroom homes need at least a closet and a place to sit.

Storage is consistently undersupplied in apartments. Residents store seasonal clothing, sports equipment, holiday decorations, tools and suitcases. A rule of thumb used by many housing providers is that about one-tenth of a unit's area should be storage of some kind, including closets. Greenway Homes also provides a storage locker for each unit in the basement or on the ground floor, a secure bicycle room with at least one space per bedroom, and a stroller and mobility-scooter room near the main entrance.

Family units

Families with children need different things from apartments than singles or couples. Children need space to play indoors in winter, a table for homework, and bedrooms large enough for two children or for a bunk bed and a desk. Parents need to be able to see and hear young children while cooking, and older children need some privacy. Families also generate more noise and more mess, so their homes need sound-resistant floors and walls and durable finishes.

Location in the building matters. Family homes work best close to the ground, with direct access to a courtyard or play area, or on lower floors reached by a short stair. Townhouses with their own doors and small gardens are the ideal; family apartments on the fourth floor, overlooking a courtyard with a visible play area, are a reasonable second best. Castellanos recalls a building in which the three-bedroom units were placed on the top floor because they could have the largest balconies; the families who lived there found that their children could not go out to play unless a parent went with them, and the units became the hardest to rent.

Accessible and adaptable units

Accessible units are designed for residents who use wheelchairs or other mobility aids. They have wider doors and corridors, a turning space in the kitchen, the bathroom and at least one bedroom, a roll-in shower or a bathtub with transfer space, lower switches and controls, and counters that can be used seated. Adaptable units are designed so that they can be converted later at modest cost: walls are reinforced for grab bars, bathroom floors are recessed to allow a later level-entry shower, and cabinets under the sink can be removed.

In the United States, the Fair Housing Act requires that, in buildings of four or more units first occupied after 1991, all ground-floor units and all units in buildings with elevators meet basic accessible design requirements, such as an accessible route into the unit, usable kitchens and bathrooms, reinforced walls for grab bars and accessible controls. Buildings funded by federal programs must also provide a share of fully accessible units for people with mobility and sensory disabilities. Greenway Homes' own standard asks for twelve fully accessible homes in this building, beyond what the law requires. The principle of universal design, developed by Ronald Mace and others, is that homes designed to be usable by the widest range of people serve everyone better, whether a resident with a broken leg, a parent with a stroller or a visitor in a wheelchair.

Exercise 2: four unit plans

This exercise takes about two weeks.

• Design four unit plans, a studio, a one-bedroom, a two-bedroom and a three-bedroom home, at 1/4 in = 1 ft, close to the Greenway Homes target sizes.
• Furnish every plan with realistic furniture at scale and show the clearances in the table above.
• Make the one-bedroom plan fully accessible and show how the others can be adapted.
• Show the wet core of each plan and how the plans fit side by side along a common service wall.
• Test each plan by walking through a day in the life of one of the test households and annotate the plan with what you learn.
• Build a full-size tape plan of one room with your group and furnish it with cardboard furniture.

Self-critique checklist

• Did I furnish the plans honestly, including storage, strollers and bicycles?
• Can one person sleep while another is awake in the living room?
• Is the bathroom reachable without passing through a bedroom or the kitchen?
• Do the wet cores line up so plumbing can stack through the building?
• Have I designed the entry for winter: room to stand, sit and store wet things?