Materials and Techniques Archives - Morehouse MacDonald and Associates

Verdant hills, violet lupines springing from the ground, rugged mountains rising and falling all the way to the horizon—it is a paradise enough to convince anyone to drop everything and race away somewhere quieter to be in nature. But even this idyllic haven faced its obstacles when it encountered the Northeast’s fiercest foe: an endless Vermont winter.

When MMA began our renovation of an aging Vermont lodge, winter’s challenges were immediately apparent. Heavy snowfall slid down the twin gables into the ten-foot gap between them, piling directly in front of the doorstep. When the sub-zero freezes took hold, that monolith of snow became a six-foot-high block of ice barring the entry.

The solution came in a single, elegant addition of a porte-cochere extending between the two existing structures. The snow slipping down the gable roofs was now redirected by the porte-cochere to heated drains located within the drive-court.

In a true marriage of form and function, the porte-cochere does more than alleviate the snow-related concerns; it also addresses the house’s uninspiring facade. By breaking up the elevation, the porte-cochere creates a more interesting roofscape for the lodge. In concert with this change, MMA introduced new colors and materials to break with the tedium of the existing plain vertical siding. The simple yet elegant color pairings and charming bay windows freshen the exterior while remaining true to the lodge’s stylistic roots.

The lodge’s new exterior aesthetic is a nod to the modernized timber-frame (post-and-beam) style interiors.

If you’re interested in learning more about this style, take a look at our post on the beauty of working with timber frames.

Working with timber frames showcases the natural beauty of wood—a fitting principle to abide when creating a home so richly surrounded by nature. Incorporating a variety of natural elements in the design has allowed us to maintain a great degree of stylistic fidelity both to the existing structure and to the architectural tradition of cabin-style homes. Meanwhile, new finishes and highly modernized kitchen and bath amenities ensure that the house’s style in no way impedes its function as a family home.

Because the lodge is, first and foremost, a home. It resides on an 1100-acre lot with another home: our Vermont meadow house (all within the family) and a working barn that houses horses, llamas, and alpacas. Summers see unimaginably bright greens; winters, never-ending flurries. But in those pale and glittering winter months, a family can park beneath an elegant roof, unload their skis, and make their way inside to the hearth, untouched by winter’s deluge.

Every now and again, a new client approaches our practice with a clear vision in their mind: they want to live in a structure that utilizes a true timber-frame approach. Often this request is infused with a sincere love for the beauty of wood. In other cases, clients have had close contact with a true mortise-and-tenon structure, perhaps hundreds of years old.

There are several approaches architects and builders can take with timber-frame structures. One approach is to fashion a structure from big timbers and connect beams and column supports utilizing ‘time-honored’ mortise-and-tenon joinery. Another approach is to replicate more industrial era techniques utilizing large and strong metal connecting plates with bolts. In both cases, architects and engineers must design timber-frame structures to meet modern-day structural and energy codes.

MMA has had the pleasure to pursue and build expertise in both approaches, including knowledge about timbering wood, sustainable forestry, how wood dries and weathers with age, and methods for applying and protecting the finish on large timber frames.

A Mortise-and-Tenon Barn in New England

As part of a comprehensive building program for a Vermont estate, MMA was asked to design a sophisticated mix-used horse barn (Vermont Barn) with living quarters for family and friends. MMA found the right partner in Bensonwood in New Hampshire, possibly the nation’s premier builder of highly-crafted heavy timber-frame homes, barns, and complex structures.

For our project, the client wanted the true feeling of a centuries-old New England barn. Bensonwood’s structural engineer Ben Brungraber led a team that directly combined three key structural components: (1) Douglas-fir heavy timbers, (2) traditional mortise-and-tenon joinery, and (3) structural insulated panels (SIPs). The approach unified 18th-century building techniques with 21st-century energy-efficient technology.

While the SIPs system added some rigidity to the mortise-and-tenon Vermont Barn project, steel tube frames that held in place the horse stall sliding doors and hardware added a line of lateral resistance.Part of the appeal of old barns is the weathered nature of old wood. As wood dries out over time timbers develop checks and splits, increasing the timber’s character. For our mortise-and-tenon barn structure, the raw Douglas-fir frame material was given a period of time to lose a percentage of its moisture within the Bensonwood shop prior to fabrication. When wood gets out into the exterior environment—as in a cold and wet New England winter—it can regain moisture in its fibers. Managing moisture content in wood members is an important step. The age-old techniques of mortise-and-tenon joinery account for the eventual shrinkage of wood as it loses its moisture over many years. At the same time, the use of the SIPs system brings a level of rigidity and tightness to a timber-frame structure.

Industrial Era Redux: Crafting Tailored Timbers and Trusses at the Marshside

While a true mortise-and-tenon timber frame structure may meet the needs of a modern barn, in some cases a building’s dimensions, plus the desired aesthetic of a structure, dictate a different approach. Such was the case of the Marshside Restaurant project in East Dennis, on Massachusetts’ famous Cape Cod.

During the 20th century, large structures started to combine heavy timbers with metal connections. This type of modern metal joinery offered a different set of benefits, such as increased structural strength, rigidity, and simplification in joinery. These benefits applied to our Marshside Restaurant project, which needed a roof structure to span 45 feet while providing the lateral resistance to higher wind loads applicable along coastal sites.

At the Marshside Restaurant, MMA worked with nationally known larger timber frame expert G.R. Plume of Washington state, who gained national prominence in unique large timber structures for the Bill Gates estate in the Seattle area.To help us, MMA turned to G. R. Plume of Washington state, one of the most innovative timber-frame shops in the world. Like the Vermont Barn project, we knew from the beginning that Douglas-fir timbers were well suited to the task, but we wanted a more tailored experience with the metal-to-wood joinery. Having developed an expert process in developing highly-crafted, and often artful wood-to-metal connections, G. R. Plume provided MMA and our structural engineer expertise and knowledge highly suitable to our goals.

Connections and Materials

In order to address the structural requirements of our project, it was decided early that MMA would employ all Douglas-fir Select Structural FOHC (free of heart center) lumber from British Columbia, Canada. Moreover, unlike the shop time-dried timber for the barn project in Vermont, our lumber was radio-frequency kiln-dried (RFKD) inside a low-vacuum microwave kiln the length of a football field. Whereas the partially green timber for the barn project was cut after it arrived at a moisture content of 20-25 percent, the RFKD lumber leaves its kiln at 15 percent across all fibers of the wood, regardless of their position within the lumber.

With this greater dimensional stability, G. R. Plume was able to provide remarkably accurate and dimensionally stable cuts and mortises for our wood-to-metal joinery. This was both structurally effective and artfully articulated, lending the timber frame trusses and columns in the project a refined industrial look that was befitting of the overall aesthetic of the restaurant’s interior and level of ambiance.

Powder-coated steel connectors were carefully inset into CNC-routed joints for member-to-member connections. ( © Morehouse MacDonald and Associates, Inc. , courtesy MMA staff, Anthony Frausto-Robledo, AIA)

The process of each connection involved three critical steps. First, MMA developed the desired look and arrangement of the steel connectors, including bolt placements and counts. The next step was for designs to be reviewed by the structural engineer and modified as necessary for strength considerations. The final step was submission to G. R. Plume to review CNC routing, general cutting, and erection sequence requirements at each joint. This final step was the most important because of the nature of the inset ‘mortised’ metal plate connectors. With such connections there is often only just one direction or axis for the wood and metal to come together and each member had to build up in sequence to form the final trusses and truss to column assemblies.

Regardless of method of timber framing construction, MMA has worked on several projects now using both methods of mortise-and-tenon and more modern metal connector joinery. The results for each are beautiful in their own way, offering a different set of aesthetic and structural considerations.