Monday, August 31, 2009

MHS offers some degree of superiority over stick frame construction


By : Eric HuntingText Color

MHS consists of a system of extruded aluminum profile posts and beams similar in nature to those of T-slot framing commonly employed in industrial automation. These are assembled in simple box frames using a concealed bolt-lock clamp which leaves the structure with a clean appearance. This is supplemented by a bolt-in-place diagonal corner brace for multi-story structures which is normally concealed within wall panels. The cladding system uses either Structural Insulated Panels or most any combination of other panel materials which slide into the special grooves of the framing profiles. The panels contribute little to no addition to structural performance so their composition is not critical, all loads being born solely by the post and beams as with traditional post and beam construction.These panels may be pre-finished, composed of materials that need no finishing, or can optionally be finished by conventional house siding, surface mount veneer board, and painted plaster board sheathing. The profile slots also readily accommodate modular window panels or composite panelwalls can be framed to accommodate more conventional windows of any shape. Roofing, supported by a simple roof truss and extruded profile solid web truss rafters, can be either conventional or, more practically, metal panel roofing. Flooring uses the same extruded solid web truss pieces as joistsand can employ any conventional flooring material. Additionally, the joists will also accommodate a clever suspended panel ceiling system. Foundation systems can be conventional curtain or slab foundations or piling foundations typical of many post and beam structures.The greatest feature of MHS is its demountability -precisely the feature that stud frame construction is lacking. With MHS one can freely and quickly disassemble, repair or modify, and reassemble structures without causing any damage to the components and materials using little more than a few hand tools. Combined with the virtues of a modular space frame geometry, this affords the system a flexibility, capability, and economy impossible with stud frame construction. The MHS building is a truly immortal structure -not because its basic materials are more resilient but because all its components can be forever replaced as they wear out and its form can be forever adapted to any use or need.

Our ancestors knew what they were doing when they first adopted post and beam construction. Before industrialization, people had to make most of the things they needed with their own hands and all such work competed for time with the more important priorities of producing food, caring for family, and preparing for seasonal changes. So people were frugal with their time and labor. They built things to last, and in those days that didn't mean futilely trying to defy nature by making things impervious to wear and damage. It meant making sure whatever you made could be repaired, reused, adapted, and recycled perpetually. The post and beam framing system achieved this capability through its demountability and modularity. By being able to be readily taken apart, any individual component could be replaced on demand without effecting the rest of the structure. By using a space frame where the loads were borne by the frame alone, weatherproof enclosure materials could be easily replaced as they wore out and the structure adapted and expanded on demand, since no walls were actually permanent. If you needed more room, you added more to the grid of the frame. If the roles of some rooms changed, you could readily remove or add walls to change the space for its new use. If you needed larger clear-span rooms, you increased the length of beams and posts around those rooms -though this had the caveat of increasing their mass greatly as well when using wood. If situations forced you to move, the whole building could be readily taken apart and rebuilt somewhere else, conserving your labor investment in its fabrication. And in the worst case situation where your house suffered too much damage to be saved or became completely obsolete, all its surviving components could be readily salvaged and directly reused in another structure. Indeed, many of the new wooden post and beam homes built today -for sake of their rustic style- use lumber salvaged from buildings more than a hundred years old!

MHS improves upon these original virtues by taking advantage of modern materials and industrial parts fabrication. Traditional post and beam structures required a high level of skill to craft their key components which tended to be large and difficult for a single person to handle. This is what compelled the old tradition of community barn raising, the components of these wide span structures being far too heavy for any individual farmer to handle alone. By using much lighter and stronger aluminum profiles fabricated by mass production, MHS eliminates the skill overhead associated with fabricating lumber post and beam components and brings the mass of components suitable for a useful range of frame spans down to a level where an individual can easily handle them. Like it's lumber predecessor, MHS still requires an increase in the length and mass of its beams as it increases in span. But because aluminum offers a higher strength-to-weight ratio than lumber it doesn't increase in required mass as fast as lumber does as required spans increase. Thus a fairly modest profile size of 6.75" is sufficient for a very wide range of spans. When the limits of this component scale are reached, the system can readily switch to the use of trusses made out of the same components, switching to a type of structural member with an even higher strength-to-weight ratio but also with a greater volume.
Another limitation of the traditional post and beam system which MHS resolves is the limited demountability in cladding and partition walls. In the past it was generally very difficult to achieve a weatherproof barrier from materials which were not monolithic in nature. Thus while the frame system of post and beam buildings was readily modular and remountable, the materials filling in the space between the frame members for walls often had to employ a compromise. Walls might be based on more 'plastic' materials like clay, cob (a mixture of clay-rich earth like adobe), wattle & daub (mixture of cob-like materials applied to a light grid of thin crossed wood strips coated in plaster) or might use siding attached with nails -even though that did damage the major frame pieces. These materials were not truly remountable but they could be very easily removed and were potentially recyclable. More remountable walls appeared in the traditional construction of Japan. They also relied heavily on their own kind of waddle & daub (though made with bamboo lathe) but complimented this with decorated paper and veneer wood panels, heavy wood planks, and paper shade screens which fit into shallow grooves carved into the post and beam frame. This was generally poorly suited to exterior walls, however, because they were so lightly and loosely attached and was more commonly employed for interiors. The Japanese also developed modular panel flooring in the form of tatami mats -an innovation that never found its equivalent in the west until the invention of raised floor panel systems for computer rooms!