Pre-approved mid-rise buildings: industrialized construction’s next big step
By Michael de Lint / RESCON
Toronto’s arterials and transit stations: mid-rise redevelopment opportunities
Toronto’s underdeveloped arterial roads (too many 2-storey buildings) and its underdeveloped subway and GO commuter rail stations (too often adjacent to detached houses), provide a big opportunity to fix the GTA’s housing supply deficit while enhancing liveability and walkability.
Premier Doug Ford’s government has already made huge progress on this issue via Municipal Affairs and Housing Minister Steve Clark’s: GTA growth plan; and his Planning Act reforms (redevelopment near transit stations); and Minister’s Zoning Orders (often fast-tracking transit-oriented residential development).
Also, Ford is tackling the GTA’s transit deficit with the long-awaited Ontario Line. This and other transit investments, support Toronto’s transition to a more mature urban functionality and form (eg. more mid-rise buildings along arterials, with step-down densities providing proper integration with established neighbourhoods).
This blog’s focus is on fully realizing these opportunities by capitalizing on new and not so new, ideas in: pre-engineered mass timber; building prefabrication; construction technology; digitization; and regulatory compliance.
Ford’s Model T: mass-production breakthrough
Over 100 years ago, Henry Ford’s assembly line allowed for mass production of high-quality vehicles with lower per-unit component and design costs. Per-car production times went from 12 to 1.5 hours. The Model T was manufactured around the world, with over 15 million units sold.
Model T Fords on the assembly line, 1920s.
We are now on the cusp of a revolution in building design and construction. New infill and greenfield development opportunities can be combined with off-site prefabrication, digital design tools supported by a creative application of regulatory tools.
North America’s long history of building prefabrication.
Prefabricated buildings assembled on-site from factory-manufactured components have been around for over 100 years. In 1918, the Sears Roebuck and Co. catalogue included prefab houses, allowing for on-site assembly of pre-cut and numbered structural and other components. More than 70,000 of these homes were sold in North America (including Canada) over the program’s 34-year history, between 1908 and 1940, with more than 370 different designs in a wide range of architectural styles and floor areas suitable for a range of building lot sizes.
Completed prefab: The “Magnolia Model” in Benson North Carolina (right), largely assembled from a prefab package, including precut lumber and other components, as described in the 1918 Sears “Modern Homes” catalogue (left). These homes included indoor plumbing and central heating as options.
Ontario firms with a history with factory-based construction (panels and or volumetric modules generally using traditional “stick” (2x6) construction), include: Great Gulf/H+me Technology (panels); modular builders such as Royal Homes; and Quality Home, to mention a few.
World’s tallest modular hotel in New York
In New York construction has started on a $65-million, 168-room, 26-storey AC Hotel at 842 Sixth Avenue, which will be the world’s tallest modular hotel.
AC Hotel in New York. Prefabricated hotel room units arrive (fully complete) at the hotel site before being lifted into place by crane, one by one. Each steel module contains one fully outfitted guest room – pre-painted, decorated and outfitted with beds, bedding, flooring, even toiletries.
Mass Timber buildings: good for occupants, neighbourhoods, the environment.
A more recent construction trend involves the use of pre-engineered mass timber structural components (beams and panels) composed of smaller wood pieces typically glued together (with water- and fire-resistant adhesives) into larger components. The adhesives used must meet strict moisture and heat resistance standards to prevent delamination under simulated severe moisture conditions over the life of the building (50 or more years), and under severe fire conditions.
Mass timber products include: cross-laminated timber (CLT) panels; glulam beams (see photo below); nail-laminated (NLT) and dowel-laminated timber panels (DLT); structural composite lumber (SCL), created by layering wood veneers, strands or flakes (with moisture- resistant adhesives) into blocks of material sawn to specified sizes. There are two types of SCL products: laminated veneer lumber (LVL), and laminated strand lumber (LSL) with panels up to eight feet wide with varying thicknesses and lengths. Another product line is parallel-strand lumber (PSL) columns. Some products provide additional functionalities such as CLT panels separated by engineered wood joists, thereby creating a cavity that can be filled with insulation, as well as electrical and mechanical systems - Ontario’s Element 5 produces such a product, among others.
Finland is simultaneously expanding its forests and pre-engineered mass timber production. In 2019, I went on a 1,000-km bus tour of Finland’s hinterland, organized by the Canadian Wood Council, where we enjoyed reindeer tartare, and saw: panelized, modular and mass timber wood buildings; factories producing modular relocatable school classrooms; pre-engineered mass timber products such as LVL and CLT; as well as large glue-laminated variable dimension mass timber beams (see photo above). In Finland, for every tree harvested four are planted. Photo: M. de Lint.
CLT modular dwelling unit Three-storey modular building
Benefits of mass timber components (eg. CLT panels) include faster, quieter and lighter construction, resulting in less community disruption at infill sites (construction with volumetric CLT modules is even faster). In addition, mass timber buildings have biophilic properties (lower blood pressure, enhanced well-being, etc.), making them especially suitable for residential, educational, office, library and medical buildings. Good building aesthetics and urban design associated with many mass timber buildings, likely contribute to additional health benefits.
Mass timber buildings, including modular, are getting taller
Buildings constructed from pre-engineered mass timber components (eg. glulam beams, CLT panels or modules) are also reaching new heights. During a 2019 trip to Finland, I toured the country’s first eight-storey, high-modular CLT apartment building (the Puukuokka Housing Block in a Jyväskylä suburb), which has won several prizes including the Finlandia Prize for Architecture. In the U.S., Milwaukee’s 25-storey mass timber Ascent tower will be among the world’s tallest.
Milwaukee's 25-storey mass timber Ascent Six-storey modular building. Source: Modular Building Institute
According to a 2019 McKinsey & Company report, modular construction is 50-per-cent faster and cuts costs by 20 per cent. The report predicts that modular could grow to a $130-billion industry in the U.S. and Europe by 2030. With upfront building costs similar to site-built, savings come from faster construction and increased labour productivity. Modular accounts for about five per cent of all new commercial and residential projects, according to Ryan Smith of Washington State University’s School of Design and Construction. In parts of Washington State and the San Francisco Bay area, modular has doubled its market share of three-to-four-storey multi-family buildings between 2015 and 2020. Further savings are possible if building design and approval costs can be spread over multiple building projects through pre-approved model designs. Ontario’s R-Haus, which recently constructed a six-storey CLT building on Queen Street, is looking at such an approach.
Pre-engineered, prefabricated, pre-designed, pre-planned, pre-approved, mass timber buildings, ideal for arterial infill development in the Toronto megalopolis (GTA)
The GTA is under pressure to fill in transit-served arterials with mid-rise buildings. These buildings could include pre-engineered mass timber mid-rise structures (including those using CLT panels, modules and exterior cladding materials as specified by local site plan control bylaws). The City of Toronto’s guidelines for development along arterial roads limit building height to the road right of way. (If the ROW is 30 metres, building height is limited to 30 metres.).
Toronto mid-rise performance standards contained in the City of Toronto’s 2010 Avenues and Midrise Study. The building height must not exceed the width of the road right of way (ROW) in order to provide a more pleasant pedestrian environment with better access to sunlight, etc. Of course, much higher buildings are often and should be, permitted near major transit stations.
In Paris, and many European cities, the predominant building form along arterial roads are mixed use mid-rise buildings (often with sidewalk cafés at ground level where people can discuss issues of the day, assuming no lockdown). In 1850, French Emperor Napoleon III appointed Georges-Eugene Haussmann to redevelop Paris (the result: famous boulevards such as Rue Rivoli, Boulevard Ste. Germaine, and others, and many new parks). These arterials feature proportional and attractive “Haussmann buildings.” Under Haussmann, street blocks were designed as homogeneous architectural wholes with individual buildings treated as pieces of a unified urban landscape. Such arterials are well-suited to mass production of pre-approved mass timber buildings using high quality designs (as in the case of the Haussmann buildings).
Creating the iconic Paris avenues required bold measures. The French Senate simplified expropriation laws, giving Hausmann authority to expropriate all the land on either side of a new street. Funds from the French parliament were insufficient, so a new investment bank financed street construction in exchange for air rights to develop real estate along the route – the model for all Haussmann's future boulevards. (As regards to air rights, several jurisdictions, including Hong Kong and Ontario, have taken such an approach to funding transit system improvements).
Boulevard Haussmann, lined by typical Haussmann buildings. The last of the major Paris arterials created under the vast public works program commissioned by Emperor Napoleon III and directed by the prefect of Siene, Georges-Eugene Haussmann. The city centre was overcrowded and a cradle of discontent and revolution. The public works program included the demolition of overcrowded medieval neighbourhoods, the building of wide avenues and parks, in order to bring air and light to the city. Haussmann developed many iconic urban parks. One of his goals was to have one park in each of the 80 neighbourhoods of Paris, so that no one was more than a 10-minutes walk from such a park – the parks and squares were an immediate success with all classes of Parisians. Between 1853 and 1870, Haussmann’s work was met with fierce opposition, and he was finally dismissed by Napoleon III in 1870, but work on his projects continued until 1927. The Haussmann building façade was organized around horizontal lines that often continued from one building to the next: balconies and cornices were perfectly aligned without any noticeable alcoves or projections. The rue de Rivoli served as a model for the entire network of new Parisian boulevards. The street-side result was a "monumental" effect, rather than buildings relying on building-specific decoration.
Alberta, B.C., Quebec and other countries ahead of Ontario
The U.S.’s IBC adopted in some states now allows 18-storey mass timber buildings. Alberta has issued a ruling (“Standata”) allowing 12-storey mass timber buildings based on proposed National Building Code changes allowing 12-storey mass timber. B.C. also permits 12-storey mass timber buildings through arrangements with qualifying municipalities. Ontario is projected to adopt the NBC’s 12-storey mass timber provisions some time in 2022. Another Ontario Building Code (OBC) impediment is the requirement for non-combustible stairways, which adds to construction complexity without a safety rationale. Impact and fire-resistant encapsulated mass timber stairwell assemblies are a potential alternative and align with proposed NBC changes.
Interior of a residential unit in a mass timber building called Carbon 12 in Portland Oregon.
Potential Ontario tools: robust pre-approved plans; alternative solutions, digitization
The Ontario Building Code Act includes tools that can be used together to expedite mid-rise, mixed-use mass timber buildings along the GTA’s arterial roads and transit station areas. Pre-approved plans provisions under 6.(1) of the Building Code Act, “Agreement re. Review of Plans,” allow for the expedited review and approval of standardized building plans of any municipality in the GTA or elsewhere in Ontario that has entered into an agreement (with the other participating municipalities). These repeat plans would need to be approved only once by the receiving municipality (perhaps co-ordinate with the others), which then issues a “pre-approved plans certificate.” This repeat plan is then reviewed by the issuing municipality only for compliance with site-specific conditions (eg. foundation, local planning). A range of mid-rise building models with different dimensions and designs could be developed that comply with local site plan requirements (that specify building exteriors, architectural features, etc.).
Pre-approved designs for mass timber buildings over six storeys and with encapsulated mass timber stairwells would currently need to incorporate an alternative solution provided for in the Building Code under the OBC, Division C part 3, Section 2.1.
Given municipal liability concerns under Ontario’s joint and several regimes – concerns that will be even more pronounced for repeat designs – a robust and bulletproof design is important. This includes a design that is co-ordinated (no gaps, conflicts among building systems) and where critical building elements (fire, structural systems) are peer-reviewed. More complete and compliant design can speed up municipal design audits and approvals. Also, repeat designs allow developer costs to be spread over multiple projects.
Finally, building and planning design elements can be prepared and approved more quickly via digital design tools such as CAD and GIS-enabled e-permitting based on a common data standard platform (a common platform is supported by the province and is being developed by One Ontario). Digitization, pre-fabrication and standardizing good design, along with a potent mix of new and old ideas, will usher in a new era in building design, construction and city-building.
A different way of thinking
Mass timber expert Steven Street sums it up nicely, “Working with creative design teams and developers ready to look beyond the next project, we need to explore industrializing our approach to design and delivery. We have a pretty good understanding of lot sizes in urban and suburban settings. Different ways to think about and approach a project are long overdue. Turn the building inside out – design the bones or structural frame and carry that knowledge into multiple projects – spreading R&D costs over multiple projects. No more one-offs – it limits our thinking, especially in multi-family mid-rise. The skin or facade designs are tailored to fit in the neighbourhoods – they are the items that change. Trades, suppliers and the entire team then become familiar with delivery, driving costs downwards.”
Says Toronto architect Marco VanderMaas, who is passionate about complete community building, “I could not have said it better myself.”
Steven Street Marco VanderMaas
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