Info-to-Build-On Wide Open Spaces by Raoul Hennin July 28, 2004 Structural posts define living spaces. What if a particular post doesn't fit the layout and flow of the floorplan?

The Shelter Institute crew builds 30-40 beautiful timber frames every year. My brother, Gaius, meets with each client to carefully engineer a structure for each unique house design. While some of our clients develop a floor plan around our standard kits, we are often asked, "what if we take out THIS post?"

A well-placed post can be a terrific asset to the flow and layout of the floorplan, but occasionally a post simply does not fit the design. In these instances, a special solution is required to resolve the heavy point loading of a timber frame structure. There are many possible solutions involving various materials and engineering know-how. A post removed can become a special feature of a timber frame and its living space.

The first consideration is always whether a heavier timber can carry the load of a missing post. The problem is that posts are much better at carrying a point load than beams. A simple calculation often reveals that no practical beam can replace a post. A wood beam can typically span 12'-16' with fairly significant loading. Beams over 20' will eventually sag even under their OWN weight!

Because trees grow natural imperfections into every timber, a typical wood beam does not take full advantage of its full 'fiber stress value.' By cutting wood into smaller pieces and then gluing the pieces back together, manufactured wood beams can significantly enhance the strength of natural wood. There are many products available in wood that afford much greater spans than natural wood alone.

Several vey strong, albeit ugly, manufactured products offer significant span capabilities. We tend use these products in first floor decks where they will be concealed from the finished living spaces of the house. Microlam and wood I-beams are good candidates for this type of solution. These products are made by the big manufacturers and are shipped across country by tractor trailor.

There is also a more attractive manufactured beam, commonly known as glulam. This beam provides a nice solution because it blends in with the natural timbers. A glulam is a timber that has been glued up from milled boards to the same dimensions as the timbers themselves. This type of timber offers 2-4 times the strength of natural timber (and costs 4-5 times as much). When sanded, oiled, and chamfered, these timbers take on the hue and texture of the rest of the frame and offer an authentic timber frame solution.

The long-term strength of wood fibers falls in the range of 1,000 #/square inch. When severe loads call for extreme strength, steel offers tensile strength as high as 100,000 #/square inch - on the order of 100 times as strong as wood! When the going gets tough from a structural standpoint, a steel beam can often solve the problem. The primary shape for structural beam steel is an I-beam, which offers terrific span capabilities. We tend to use steel most often in the first floor deck where it is concealed from the finished living space.

The final solution for broad, uninterrupted interior space is structural trusswork. A truss draws incredible strength from its own geometry. While a computer can help analyze the structural loading of trusses, there is a high art to selecting appropriate materials, connections, fasteners, and geometry to create a successful, beautiful timber truss. In large open-span rooms, there really is no substitute for the modern ingenuity, tradition, and craftsmanship of a timber truss.

In designing timber frames around living, working spaces, Gaius uses his Professional Engineering background to develop customized solutions for each structure. Choosing from a wide array of options, he is selects just the right combination of materials and methods to accomplish what is most important to each individual space. I have first-hand experience because Gaius helped me design my barn last year. We replaced several of the posts with heavy timber trusses (above left) to create incredible wide open spaces in the barn. My only regret is that the building is now done - and I am trying to dream up an excuse to design and build again: it is addictive.

The Shelter Institute classroom (above right) uses traditional all-wood joinery in a 30' king-post truss. Gaius' own barn bays are clearly defined by solid carrying posts every 12'. After all, when it fits the floorplan, a post is the most direct way to carry a load.

Learn to build your own house at the Shelter institute. See our entire 2004 class schedule online at:
http://www.shelterinstitute.com/classchedule.htm