Plas-2-Point House by Marcel Breuer (1943)

Architect/Designer: 
Model Overview: 

With the Plas-2-Point Breuer continued his investigation into prefabricated housing begun a year earlier with the Yankee Portables project.

The house's plywood substructure was to be given a thin coat of liquid plastic by the plastics manufacturer Monsanto, a novel take on traditional sealants that would render the entire structure more durable and easier to clean. Even more inventive was the fact that the structure touched the ground at only two points, anchored to foundation blocks that eliminated the need for any expensive grading or full foundation work. This greatly decreased the amount of time necessary to assemble the house.

Connecting the two anchor points was a massive central girder from which radiated a tapered truss system—inspired by the trussing of an airplane wing—on either side. Vertical posts supported another spinal girder, which had a trussing system identical to that of the floor system. Modular plywood panels could be configured in variations to form the roofing, flooring, and interior wall divisions. The house contained two bedrooms, a living room, dining area, kitchen, and terrace. The two anchor points would barely be visible at ground level, giving the entire structure the appearance of hovering above the ground slightly, like an airplane about to land or, perhaps, take off.

Breuer had a model built of the project and used it as part of his design curriculum while teaching at Harvard. His students took active roles in developing the scheme and subsequently building the model under his supervision. Monsanto Plastics published a feature article on the project in the October/November 1943 company magazine, in which Breuer issued a statement on the powerful role that plastics could play in the future of prefabricated housing, remarkable considering that the project anticipates nearly twenty years other plastic monocoque designs. As with the Yankee Portables, the Plas-2-Point was pitched as postwar housing to officials in Washington, D.C., but the project would never get off the ground, feeding Breuer's increasing frustration with the inability of architects to break into the prefabricated housing market in the United States. In Breuer's eyes, the future of the prefabricated house would unfortunately rest within the hand of "commercial fabricators who don't bother with architecture."

 (Source: Home Delivery: Fabricating the Modern Dwelling by Barry Bergdoll and Peter Christensen)

 

Design Style: 
Modern
Construction Methods, Materials and Features: 

The Plas-2-Point house is a stick frame and plywood structural system. The roof consists of a plywood girder which runs along the apex of the roof (the ridge) and acts as a stabilizer for the roof trusses. Vertical loads applied on the roof would trav el through the roofing material (plywood sheathing) and into the top chord of the truss, which resists the load by acting in compression. the wall panels are acting in tension; therfore, in the absence of a vertical load, the top chord of the truss would be in tension, because the walls are exerting a downward force on the ends of the truss. As such, the top chord of the truss could be said to be pre-tensioned.

The load is then primarily transfered from the top chord of the truss to the plywood ridge beam. Additionally, two purlins run on either side of the ridge beam, about halfway between the ridge beam and the side walls. These members resist the load in be nding, which occurs due to the existence of both tensile and compressive forces within a structural member. The load is then transferred to the intermittent vertical members of the truss, which are acting in compression. The vertical members of the trus s are transferring the load down to the bottom chord of the truss, which is acting in tension, due to the downward force exerted by the vertical load on the top chord of the truss. Because of the tension in the walls, the bottom chord of the truss could possibly be said to be pre-stressed in compression.

The entire roof load (both live and dead loads) must be transferred downward through the plywood ridge beam and onto one of two columns which support the ridge beam at either end. Initially, however, the ridge beam and the two purlins are supported by a triangular end panel, at either end, which in trun transfers the load onto the two columns. These columns obviously act in compression, and transfer their loads downward onto a plywood girder, similar to the ridge beam, which supports the floor structure . The floor structure appears to be a mirror image of the roof strucutre. The members that were acting as framing for the roof are inverted and used as joists in the floor, and the ridge beam and purlins in the roof are replicated and used as load-bearing supporting girders for the joists in the floor.

The plywood supporting girder which acts in compression and bending transfers the entire load of the structure onto two foundation blocks which in turn, transfer the load down into the ground by acting in compression. The majority of the floor structure is cantilevered beyond the two foundation blocks. Again, this was intended to reduce the cost of these houses by eliminating the need for a foundation.

As mentioned above, the side walls of this structure are in tension. This serves to pinch the structure together on both sides, adding stability. By designing the walls to act in tension, Breuer ensures that the entire load of and on the structure is transfered through the two end columns, which are acting in compression.

The pre-tensioned side walls serve as lateral stabilizers for the structure as well. A leteral load applied to these side walls would be transferred through the end walls, acting as shear walls, into the roof and floor structure, and be resisted by the two end columns. These two end columns would then transfer the lateral load down into the ground via the two foundation blocks. A lateral load applied to the end walls of the building would in part be reisited by the side walls as they act as shear walls to provide bracing against the shear components of the lateral load. Additionally, the two foundation blocks would resist a lateral load applied to an end wall.

What is not clear is whether or not the building is attached to the ground at any other point other than the foundation blocks. It seems that this building would want to topple off its foundation blocks when the side walls were subjected to a lateral loa d. We believe that there must be some sort of moment connection between the plywood girder and the foundation blocks, although we are not sure exactly how this could be achieved, as moment connections are difficult to execute between wood and concrete. We surmise that the concrete piers are shaped in such a way as to cradle the floor trusses at the plywood girder to prevent the structure from toppling.

It is a very light and simple structure, ideal for mass prodution, and perfectly able to withstand the loads of the single family within, as well as the live loads of mild climate areas.

(Source: Univ. of Oregon)

Construction Methods, Materials and Features: 
Timber Frame
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