Part 1
The Modular Housing System of US SYSTEMS presents a radical new approach to housing construction offering new freedom and capability for the home owner and a new economic model for the housing market. Here we will compare MHS to conventional housing, illuminating the key advantages of this new construction system.
Contrary to popular belief, the wooden stud or, as it's sometimes called, the 'platform' framing system commonly used in contemporary housing is a rather recent invention which had its origins in a building technique called'balloon' framing which appeared in the US Midwest in the 1830s and was popularized by early Do-It-Yourself carpentry and construction books and magazines. Up until that time the predominate framing system for housing construction was the post and beam system which had been in use for thousands of years and which has its variants in every culture and civilization in the world. Stud framing method was developed primarily as a means to save labor and materials, trading the use of skilled carpentry with nail-less joinery for quick and easy nailed construction and large heavy pieces of lumber for smaller lighter pieces that were easier for one person to handle, easier to transport, and which allowed the lumber companies to get a larger percentage of usable lumber out of a given tree with less waste.
Stud frame construction did not start to become ubiquitous for American housing until the 1920s-1930s with the import of the 'garden city' concept from Europe, the growth in automobile use, and the subsequent growing demand for housing outside of urban areas where, for fire safety, masonry had become the predominate construction material. The labor saving, reduced skill virtues of this technique and its use of cheap small piece lumber appealed to builders -especially the mass housing developers that emerged during the post-WWII housing crisis. They faced problems of a need for rapid large volume construction and a steadily declining quality and rising cost of wood. This building technique offered a means to build quickly with what used to be considered quite inferior grade lumber, this virtue aided by the adoption of composite wood products which made what was formerly lumber production waste into a usable product.
Over time this trend to make nominally durable structure from materials of steadily declining quality has evolved into an increasing dependence on the products of organic chemistry. The diagonal dovetail board cladding of early 'balloon' framed structures was replaced by adhesive bonded plywood which now is itself being replaced by Oriented Strand Board made of even cheaper wood and cellulose fiber scrap bound together with more adhesives. The early wood lath supported hand plastered interior wall covering, with its often intricate molded plaster details, was replaced by a laminate of paper and gypsum called 'plaster board' or 'sheet rock' and is now giving way to various forms of paper composite board. The humble 2x4 is now being replaced by laminate lumber made of glued wood strips and wood trusses made of OSB and thin laminate wood pieces. And most recently the whole stud frame system is starting to be replaced by Structural Insulated Panels -a sandwich of OSB and styrofoam. All-in-all, there really isn't much that one could call 'traditional' about this conventional building method. It became the standard simply because it was fast and cheap, and nothing more. And if the current materials trends hold true, it looks like stud frame construction will ultimately evolve into a system where houses are nothing more than various forms of composite paper held together by and wrapped in plastic.
Stud frame construction is based on the concept of a stressed skin structure where the frame and its cladding combine to function as a whole load-bearing system. It's quite similar in nature to the monocoque structures of aircraft, affording a high strength-to-weight ratio but at a cost of a high number of individually fragile components -as anyone who has built model airplanes knows well. In the original 'balloon' framing system the stressed skin structure would be fashioned to span all stories of a home and be unified by a cladding of dove-tail joined planking in a diagonal pattern. In the more contemporary 'platform' system each floor is framed independently and clad in plywood or Oriented Strand Board creating a system of stacked single-story boxes. Altogether, this is an adequately strong and efficient system with great initial design flexibility but it imposes severe limitations on performance and later adaptation.
Structural Insulated Panels represent the latest innovation in this building technology and may eventually replace stud framing while remaining essentially the same building system. Composed of a sandwich of semi-rigid foam insulation and Oriented Strand Board with an edge frame of conventional stud lumber, they function as stressed skin structures in the same way as the stud frame but eliminate all the assembly of intermediate studs and offer the further bonus of built-in insulation. One simply erects the panels in the same places one would build a stud frame and nail them together at their edges. SIP panels offer higher strength-to-weight ratio than stud frame structures and are very quick and easy to assemble but are far more dependent on chemistry for their performance than anything previous. Some have questioned their use as an exterior wall system because of Oriented Strand Board's greater susceptibility to moisture and the potential for deformation of the panels in the event of moisture infiltration -though, of course, polymer chemistry will probably arrive at some quick solution for that too. It's a great labor savings innovation, but also one that amplifies all the inherent limitations of the stud framing it replaces by an order of magnitude!
The greatest limitation of stud frame construction is its non-demountability-its inability to be taken apart without destroying it in order to repair or adapt its structure. With this system walls are the primary load-bearing elements and their arrangement becomes critical to the structural performance of the house. Once built, it becomes very difficult to rearrange the layout of a stud frame home because of the impact of such changes on structural integrity. Change too much and the whole home comes down. Most home designs try to ameliorate this limitation by putting the load bearing dependence primarily on the exterior walls and a few select key interior walls which are assumed to be less likely to need later changes. Innovations in roof truss systems have expanded this capability, allowing for larger clear roof spans with most of the roof load on the perimeter walls alone. But room spans can still be very limited with this system and when homes are expanded at their perimeter it becomes impossible to remove those key load bearing walls when they suddenly become intermediary walls without radical modification of the roof and floor systems.
Continue....
