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Designing Flexible Housing

Summary | How the Strategy Works | Advantages and Issues | Sources | Case Study #1 ]

Grow Home — Montréal, Quebec


Create an affordable ownership housing form where the interior can be adjusted or modified incrementally to match the space requirements and financial situation of the homeowners.

Target Group

Low- to moderate-income households.


The Grow Home is a three-storey townhouse that is 4.3 metres (14 feet) wide and contains approximately 93 m² (1,000 sq. ft.) of space. The Grow Home begins with a small living room, dining room/kitchen, bathroom, and one or two small bedrooms on the second floor. At the time of purchase, the Grow Home’s upper floors are not partitioned. As the homeowners’ need for space increases and their financial condition improves, they can progressively adapt the house — in whatever way they choose. For example, the owners may turn the unpartitioned space into another bedroom, a larger living area, or maybe a home office.


Background and Context

Avi Friedman and Witold Rybczynski of the Affordable Homes Program in the School of Architecture at McGill University developed the Grow Home concept in 1990. The purpose was to create a home that could be built to be affordable to low- and moderate-income households.

Visitors to the demonstration unit provided information that helped the design team determine if there was a market for the Grow Home. Of those visitors surveyed, three quarters said they would live in a house smaller than 93 m² (1,000 sq. ft.); 93 per cent approved of a second floor that could be completed according to their needs; more than two thirds thought the Grow Home was a good buy; and the traditional row house appearance of the Grow Home appealed to 94 per cent of the visitors surveyed.

How it Works

A Grow Home is a narrow front, three-storey townhouse with a floor plan of 4.3 m by 11.0 m (1  ft. by 36 ft.), or about 46.5 m² (500 sq. ft.) and a fixed, hard shell, as well as a structural core, enclosing soft, flexible interior spaces that can be reconfigured, rearranged and expanded upon in the future. When homebuyers purchase a Grow Home, it comes with a finished first floor containing a kitchen, bathroom and living space. One or more upper floors are typically unfinished at the time of purchase. They are also arranged in an open concept, which means that their interior spaces are large, and open to each adjacent space, minimizing the use of interior enclosures and private rooms. In general, an open-concept space does not have defined interior boundaries or barriers such as walls and doors that traditionally delineate one space or functional area from the next. Essentially, in an open-concept plan, one room can serve multiple functions, take on multiple configurations and support a range of occupancy types over time. The floor plans for the main and upper floors show a typical Grow Home (after the second floor is filled in).

Typical Grow Home Floor Plans
Source: Avi Friedman and Vince Cammalleri (1994). Evaluation of Affordable Housing Projects Based on the Grow Home Concept, prepared for CMHC, p. 26

The buyers specify the layout of the main floor before the purchase. At a later time, as their space requirements increase and financial situation improves, they can finish the upper floor. Plumbing and wiring can be reached easily through removable floorboards, so the homeowners can alter the layout of the interior walls to suit their evolving lifestyle needs.

Typical Montréal Grow Home
Source: Building and Social Housing Foundation

Planning and Design

The design and planning for a Grow Home are based on a progressive and planned housing strategy for affordable homes that shares several of the fundamental principles of building houses incrementally. These principles include:

  • Flexibility: To allow for flexibility, the design should look well into the future of the home, as well as its long-term uses and configurations. A design that allows for flexibility provides the initial home with options and strategies for expansion and adaptation of its interior configurations, as well as its exterior finishes, over time. To achieve these changes, the construction systems and the building materials being used must also be flexible.
  • Anticipated change: Incremental growth plans for the future expansion and completion of unfinished areas that are constructed without completed plumbing, wiring or ductwork—elements that will be finished in the future. These unfinished areas are equipped with the structural foundation to support future growth and anticipate any needs for future structural configurations.
  • Owner participation: Planning for incremental growth is tooled to the financial growth of the specific homeowners and, thus, must carefully involve their participation. As the homeowners’ financial situation improves, they can advance the completion of their home. This not only makes the initial costs of construction lower but also renders future expansion and growth more affordable, as these phases are anticipated in the structure and original design of the home. Owner participation also allows for “do-it-yourself” construction, where owners can hire their own builders or do any future renovations themselves.
  • Non-disruption: Planning carefully for future change allows homeowners to avoid any significant disruptions to their lives as they adapt and complete their home in the future. The design allows homeowners to avoid unnecessary costs for demolition, reconstruction, moving and labour required to make upgrades to the home.

An example of design for incremental growth can be a new homeowner who wants to construct a home but is unable to immediately afford the complete “finished” home with all the wanted features. In this case, an incremental housing project allows for the construction of one or two unfinished areas and possibly a basement. The structure and skin of the building are in place but can be at various stages of completion. However, their construction anticipates the future growth of the home. The other areas remain unfinished. In total, the home provides one or two bedrooms, living space and basic levels of utilities (if any at all). Over time, as the homeowner is ready, more living space can be constructed, new interior walls can be built up and greater delineation of interior spaces can occur. As the family expands to potentially include more members, the additional areas can be finished, extra bedrooms can be added and the overall completion of the home becomes more realized. Changes can also be made to the number of floors in the home. The homeowner can build additional floors on top of the Grow Home, as local codes and construction costs permit. Over time, changes will occur to add finishing and details to both the interior and exterior of the home.

Partners and Clients

The initiative for the Grow Home concept began in 1990 as a university-led study on possible delivery methods for affordable homes available to low- and moderate-income households. This quickly caught the attention of private sector builders who helped bring this concept to reality. This partnership resulted in over 6,000 dwellings being built over the next two decades in Montréal, and roughly another 4,000 in communities throughout Canada and the United States.

In this partnership, research led by McGill University has helped to analyze homeowner satisfaction and trends in ownership over time. This has allowed for a greater understanding of how the model responds to affordable housing needs and how it achieves the concepts of flexibility, growth and owner satisfaction that were central to its original conception. The close connection between the private construction sector and institutional research at McGill University ensures that the model stays current and innovative and continues to respond to the challenges of design innovation in affordable home delivery for low- and moderate-income households.


The affordability of the Grow Home model lies in the construction systems and design of the home itself, generally not requiring external financing mechanisms or partnerships to supplement the costs of purchasing. This allowed for the original Grow Home concept to develop affordable homes for low- and moderate-income families without government support or financing.

The cost of today’s Grow Home would depend on the location of the construction, the cost of the land and the availability of materials. When considering its original Montréal context, the Grow Home continues to achieve significant cost savings of at least 30 per cent, when compared to conventional single-family homes in the area.

How Savings are Achieved

The cost savings of the Grow Home are achieved in several ways:

  • Grow Homes are built on small lots, thereby reducing land costs.
  • The small lot size and high density reduce the per-unit hard infrastructure costs by 60 per cent compared to single-family houses on regular lots.
  • Small building size reduces the labour and building materials needed for construction.
  • Different options are available to homeowners to customize the Grow Home to allow them to make trade-offs between amenities and their budget. For example, an owner can add a balcony, a sloping dormer roof with a window, a deck, or even Georgian-style strip moulding.
  • Homeowners are given the flexibility to construct their home in relation to their own personal finances and budget.
  • The construction of the Grow Home supports future expansion and addition, such that renovations and additions are not unnecessarily expensive. This is done by building flexibility into the housing design, such that the structure and shell put in place at the outset anticipates and allows for future changes to the house.
  • Each floor left unfinished reduces construction costs considerably.
  • Lower upfront development costs reduce monthly mortgage payments, making ownership attainable to young families and first-time homeowners, often at costs below the average rental rates in a given market.
  • The Grow Home has one third the exterior wall area and one-half the roof area of a conventional detached house, thereby reducing energy costs for heating and cooling accordingly. On average, annual heating costs in a Grow Home are 40 per cent of the costs in a conventional detached house.

Impact on the Provision of Affordable Housing

How the Project Created Affordable Housing

Following its introduction into the North American housing market, the Grow Home had significantly lower construction costs than other similar completed homes in Montréal. Over time, Grow Home units were not only selling for much less than conventional homes but were successfully and seamlessly being incorporated into the fabric of Montréal suburbs, as well as communities around North America.

The project’s immediate market success was visible one year after the first demonstration home was constructed on the McGill campus as 87 Grow Home units had already been sold. This number grew to 1,000 homes built in and around Montréal by the second year in 1992, and to over 10,000 Grow Home units in North America by 1999.

These successes brought a greater understanding of the provision of affordable housing in North America. A demographic study revealed that the majority of Grow Home buyers were young couples, with or without children. This, seemingly, was the population most interested in purchasing a home into which they could grow — favouring incompletion and flexibility over completion and immediate gratification. The remaining owners were either single-parent households or single persons. Thus, the Grow Home provided an opportunity for low- and moderate-income households to enter the homeownership market and gain access to flexible and adaptable housing that could grow with their financial situation.

Today, the Grow Home model has influenced numerous affordable housing projects across the country. Several of these Grow Home communities can be found particularly in Montréal’s east end, where the Grow Home concept has flourished in response to the demographic need for housing. When the flexibility is coupled with economies of construction and affordable financing mechanisms, the provision of affordable housing based on this model increases greatly.

Suitability for Replication

  • The Grow Home units that have been constructed throughout North America and Eastern Europe indicate that the concept can be transferred to different municipalities and housing markets.
  • While the cost of the land on which to construct Grow Home units will vary from one municipality to another, the cost of materials and labour should be very similar.
  • An important precondition is a willing municipality that will incorporate flexible lot sizes into its zoning bylaws.
  • The Grow Home model has been applied in both urban and suburban settings. While the compact size of Grow Home units makes them suitable for infill and small lot applications, such homes have also been built as stand-alone dwellings in new subdivisions.

Related Strategies

Sources of Further Information

  1. For additional information on the Grow Home, see the feature article on the World Habitat Awards website at

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