The New Plex
© Philippe Fournier 2023. All rights reserved. Reproduction prohibited unless advanced written permission is granted by the author. Final self-directed research project completed in fulfilment of the requirements for the Master of Architecture degree at McGill University. Summary: A multiplex is a low-rise multifamily residential building with two or more separately accessed dwelling units, built at a similar scale to a traditional house. To address severe housing shortages, many jurisdictions across North America and around the globe are reforming long-standing zoning laws to permit multiplex construction across vast areas of land which formerly only permitted building single-family houses. This opens up a new frontier of design possibilities for builders: how should these buildings be designed? Though well established across the province of Quebec and once historically common in many other places, multiplexes are rare in the rest of postwar North America, with the majority of private households now dwelling in single-family detached houses. The scale of the housing crisis demands a radical expansion of denser building stock, but the carbon intensity of large-scale new construction poses environmental problems. As an example of ‘missing middle’ housing, multiplexes have many advantages which make them opportune for addressing both the housing and climate crises simultaneously. While increasing density and housing options, plexes have the advantage of being small enough to construct in light wood frame, embodying low carbon and employing local materials and trades. Their human scale and adaptability can allow them to blend unobtrusively within the built character of many established suburban neighborhoods. Their low capital requirements would permit a competitive market to emerge among small builders, while their rapid constructability lends itself well to prefabrication and other efficient construction techniques. This project revisits historical North American multiplex designs, makes the argument for streamlining multiplex construction in contemporary infill suburban contexts, investigates their regulatory and practical constraints, and explores ways of designing the typology in order to improve its environmental performance, cost effectiveness, and above all the quality of life for residents.
© Philippe Fournier 2023. All rights reserved.
Reproduction prohibited unless advanced written permission is granted by the author.
Final self-directed research project completed in fulfilment of the requirements for the Master of Architecture degree at McGill University.
Summary:
A multiplex is a low-rise multifamily residential building with two or more separately accessed dwelling units, built at a similar scale to a traditional house. To address severe housing shortages, many jurisdictions across North America and around the globe are reforming long-standing zoning laws to permit multiplex construction across vast areas of land which formerly only permitted building single-family houses. This opens up a new frontier of design possibilities for builders: how should these buildings be designed? Though well established across the province of Quebec and once historically common in many other places, multiplexes are rare in the rest of postwar North America, with the majority of private households now dwelling in single-family detached houses. The scale of the housing crisis demands a radical expansion of denser building stock, but the carbon intensity of large-scale new construction poses environmental problems.
As an example of ‘missing middle’ housing, multiplexes have many advantages which make them opportune for addressing both the housing and climate crises simultaneously. While increasing density and housing options, plexes have the advantage of being small enough to construct in light wood frame, embodying low carbon and employing local materials and trades. Their human scale and adaptability can allow them to blend unobtrusively within the built character of many established suburban neighborhoods. Their low capital requirements would permit a competitive market to emerge among small builders, while their rapid constructability lends itself well to prefabrication and other efficient construction techniques. This project revisits historical North American multiplex designs, makes the argument for streamlining multiplex construction in contemporary infill suburban contexts, investigates their regulatory and practical constraints, and explores ways of designing the typology in order to improve its environmental performance, cost effectiveness, and above all the quality of life for residents.
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Flex Plex
Typical Floor Section
STC: 50-54
Fire Rating: 1hr
Thickness: 12-1/2” (318mm)
x1 layer 1” [25.4mm] (nominal) Wood Finish Flooring
x1 layer 1” [25.4mm] (nominal) Wood Panel Subfloor
x1 layer 2” x 10” [38 x 235 mm] Wood Joists, 16” [406 mm] O.C.
3” (minimum) insulation
x1 layer 1/2” [12.7 mm] resilient channel, 25 ga. (0.018”), 24” [610 mm] O.C.
x1 layer 3/8” [9.5mm] Type X Gypsum Lath
x1 layer 1/2” [12.7mm] 1:2 - 1:3 Gypsum Sand Plaster
x1 layer 1/2” [12.7mm] Gypsum Panel (Type ‘X)
Typical Interior Demising Wall Plan
STC: 60
Fire Rating:
Thickness:
1hr
9-1/4” (235mm)
x1 layer
x1 layer
x1 layer
x2 layer
5/8” [15.9 mm] Sheetrock® Gypsum Panel (UL Type SCX)
2” x 4” [38 x 89 mm] Wood Studs, 16” [406 mm] O.C.
1” [25.4 mm] air space
2” x 4” [38 x 89 mm] Wood Studs, 16” [406 mm] O.C.
3-1/2” [89 mm] insulation
5/8” [15.9 mm] Sheetrock® Gypsum Panel (UL Type SCX)
Typical Exterior Wall Plan
Max Extent, Exterior (Masonry Veneer)
Thickness:
x1 layer
x1 layer
x1 layer
x1 layer
x1 layer
up to 17-1/6” (437mm)
5/8” [15.9 mm] Sheetrock® Gypsum Panel (UL Type SCX)
1/2” [12.7mm] Plywood Sheathing
Vapour Barrier
2” x 4” [38 x 89 mm] Wood Studs, 16” [406 mm] O.C.
3-1/2” [89 mm] Cellulose insulation
1” [25.4 mm] air space
2” x 4” [38 x 89 mm] Wood Studs, 16” [406 mm] O.C.
3-1/2” [89 mm] Cellulose insulation
4” [100 mm] Gutex Multitherm Wood Fibre Insulation Board
Waterproofing Mmebrane
Exterior Finish TBD by Builder. Control Layers as required.
Typical Details
The Flex Plex incorporates three typical separation
detail: interior demising walls, interior demising
floors, and exterior walls. The interior demising wall
and floro assemblies provide a minimum 1hr fire
rating and STC rating over 50 to miniimize sound
penetration between units. Other non-loadbearing
partitions interior to the units themselves assume
typical wood stud walls and gypsum with finishing
up to the builder’s discretion. Exterior walls are
provided with minimum R-40 insulative values
using biogenic cellulose and wood fibre insulation.
Though drawn to assume a maximally thick masonry
veneer wall, exterior cladding material outboard
to the thermal envelope is left to the builder’s
discretion to allow for aesthetic personalization
and variability.
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