SUBS #3:
Modular Geometry for Simple Universal Building System

The obvious choice for a standard modular construction panel size is 4' x 8'.  It's a common standard for plywood and other building materials.  It's a good height for normal ceilings.  It's also twice as long as wide, which makes recombinant geometry elegant.

To mix and match building panels, it is very desireable to have a fundamental design modulus that is combined in integral mutiples to create standard geometrical forms which mate easily.

One foot is too large for the fundamental unit as it's much too big for the minimum panel thickness.  That defaults the modulus to 1/2 foot, or 6".  That's the approximate thickness of a stout wall, and flooring on 2x6's can be extended up to twelve foot spans for light duty, so it's good enough for most uses.   For extremely long spans or industrial duty, a doubled or even thicker panel will combine perfectly with single thickness ones.

So the basic panel is 6" thick x 4' x 8', or in the design modulus, 1 unit [6"] by 8 units by 16 units.  10' and 12' plywood are available to make longer one-piece panels for longer floor and roof spans.  The same geometry extends simply to these longer units.

The "obvious" metric panel dimensions of 1/8 meter [12.5 cm.] thick by 1 meter by 2 meters isn't tall enough for ceilings, so they have a geometrical mess in spite of their "perfect" system, and often use a panel 1.2 meter by 2.4 meters.  I don't know if it is 15 cm. thick or not, to keep the 1/8/16 geometrical rations.  I understand the Japanese also have two different panel systems based on 0.9 meter modules!  The english system solves this problem much more elegantly.

The basic geometric subunit of most panels and parts is a six inch square with a "potential" hole in the center.  I see it as a six inch square with an X joining the corners to show me the center.  You can visualize them edge to edge around the outside of the 4' x 8' panel, and tiling the surface.   These X's mark the modular points to join panels.  Whether you make the panels 2' x 8', 4' x 12', 3' x 10', or whatever, the modular units will always show you exactly where to put the connectors.

The obvious way to connect panels is with bolts.   They are simple, cheap, incredibly strong, and can easily be put together and taken apart, which allows for modular structures that can be simply assembled and disassembled indefinitely.

So a 4' x 8' panel would have a hole approximately every four feet on each side around the perimeter.  On each end, there would be two holes, one at each corner, 3" from the end, in the center of the panel [3" from each edge].  On the sides, there would be the same two at the ends, and in an additional one of the two modules on either side of the 4' mark center length of the panel.  In practice, I would drill both of the center holes, but only bolt one in assembly, so in the run of an 8' wall, each panel would typically be bolted to adjacent panels with three bolts.

The beauty of this geometry is the design is universal.   Now established, it can be executed in any material.  Fiberglass would make an excellent strong and light panel.  Metal would be excellent for many applications.   Other materials and fibers may well be useful.  The "open architecture" [to borrow a phrase] geometry itself allows you to mix and match panels of different materials and purposes just as simply as mutliples of the same unit.

This design can also be very conveniently executed in wood.  Frame 3/4" ACX or better plywood on 2'x6' studs [wrapped around the edge with one stud/rafter/joist in the middle] and you have a panel which meets code for flooring, and exceeds code for walls and roofs.

A "2 x 6" is actually normally about 5.5 inches wide, so I trim it down 1/4" to 5 1/4" so lumber framing plus 3/4" plywood sheet equals the 6" building unit.  This is still plenty strong for an 8' span panel.  By using two center studs and douglas fir machine tested lumber for framing, you can get up to twelve foot spans in wood before needing a foot thick panel.

The plywood skin is glued and screwed to the framing with 2" or longer screws on 6" centers.  The framing joints are end-screwed with 3" or longer screws, as well as joist hangers for the center stud(s).  The framing corners away from the plywood are a stress point and may need metal connectors with mutiple smaller screws for high stress or tension applications.  I designed a simple strong one but there are many possible variations.

This produces an enormously strong ONE PIECE prefabricated panel that can be simply and easily bolted up to it's clones and anything else using the modular geometry.  The 1.5" thickness of commercial lumber is a convenient 1/4 of the 6" design unit.  Where panels adjoin each other, you have a 3" x 6" framing member [actual, not nominal dimensions] at the edge of every panel.  The plywood skin [conveniently 1/8 of the design modulus thick] actually has MORE load strength than the studs, which mostly serve to keep it from flexing.

Though studs are slightly less than 24" on center within a 3-stud 4 four foot wide panel, the doubled edge studs make an effective "average" distance of about 16" on center between studs.  If you go to two center studs [for a total of four in extra long or heavy duty panels] you have an effective average distance of 12" on center between studs for span tables.

Since the bolt holes are all in the center line of the panel edge, a panel can be faced either "in" or "out" relative to the panels adjoining it. It makes no difference, as the geometry is exactly the same.   The same panel can also bolt in with either end "up", so you have complete alignment flexibility in the design matrix.

For a typical housing panel, 1/2" grade two bolts would be a good choice.  Fine or coarse threads would work.  1/2" hole large malleable timber washers would be used on all timber surfaces.

In wood, this entire panel could be spray or even dip painted when constructed to weatherproof every surface before building assembly.  For a little extra expense, the inner parts of the walls/roof/floors can be weatherproofed too.  This cheap insurance in case of leaks, and vital extra protection for critical areas such as bolt holes and corners.  It also protects panels stored outdoors before or after assembly.  The paint can be much better applied in the shop than in the field.  Once bolted together, unpainted surfaces would be impossible to protect and would tend to trap and hold moisture.

This general geometry could be imitated by other materials in different thicknesses.  A metal panel could be very thin but very strong and still define a volume of 6" x 4' x 8' (etc.), with bolt holes at the exact same perimeter points as wood or fiberglass panels.

This standardized geometry is the key to allowing different industries to use different materials and all produce interchangeable components of the Simple Universal Building System.

It allows generalized design to be executed in many variations depending on local materials, intended purpose, etc..

It allows the potential of a universal architecture which is locally unique but completely translatable.

It allows for a standardized modular architecture to create, not a standardized Leavittown mass produced house of horror, but an infinitely variable user defined and constructed life-art structure, transforming the owner builder into instant architect to create and dwell in his own fantasies.

Bill Dur <billdur@net-prophet.net>

modular.systems * Simple Universal Building System * "Superior By Design"