CONSTRUCTION METHODS

The first substantial structure we built was a straw bale cabin and we were immediately hooked on the beauty of the bale walls and the low environmental impact of the construction. We were already experienced with conventional stick framing construction and were impressed with its efficiencies, but we had a gripping fascination with timber framing that wouldn't let us rest. After moving to Central New York, with its cold wet climate, we put straw bale and timber framing together and found it to be a very high performing and aesthetically unmatched construction method. Along the way we experimented with other construction techniques, such as, double stud construction, earth bags, living roofs, light clay straw, cob, rammed earth tires, and earthen floors. Below we highlight three methods that we use the most and have found to work best in our climate.


TIMBER FRAMING

We join posts and beams with traditional joinery methods which are completely exposed to the interior space. The visible mass of the surrounding structure and carefully crafted mortise and tenon joinery can be stunning even in it's most basic form. The durability of timber frames is evident from neglected old barns in the countryside that refuse to give up easily. Minimal processing along with durability make timber framing a good environmental choice, since timbers are sawn green and little cutting is necessary.

We prefer to use locally available white pine timber which is easy to work with, has minimal shrinkage when drying, and is both economical and beautiful. We have built with many other wood species as well, including dramatic woods like black walnut, but be aware that hardwoods add to the material and labor costs. We like to incorporate natural tree forms and enjoy adding curved timbers to bracing and truss work.

Timber frame structures do require some extra design considerations to create an affordable and workable home. Maximum spans and available timber sizes should guide decision making of the size and shape of a building. Foundations need to be adapted to accept the point loads of posts. Plumbing and electrical lines need to be mapped out ahead of time and routed around timbers if necessary. Bracing and their relation to window locations and chimney routing should all be thought out ahead of time to avoid unsightly or unseemly solutions.


STRAW BALE WALLS

The thickness of straw bale walls and their curvaceous and undulating form compare favorably to the beauty of adobe buildings of the Southwest and the old cob buildings of Europe. Bale walls have the advantage of being much faster to build with the added bonus of excellent insulation values. Straw is a readily renewable resource and the bales possess very little embodied energy or toxicity – making the environmental impact of straw bale construction very low compared to more conventional wall building methods.

In our wet climate we find it easier to build bale walls after the roof is complete. A timer frame house is at some point a pavilion with a fully braced timber frame supporting a roof. The bale walls wrap around and are fastened to the outside of the timber frame. Bale walls can be built on any type of foundation including concrete slabs (with a stem wall to raise their elevation) or standard wood floor decks over a basement or crawl space.

Plaster is an essential part of bale walls, protecting them from weather, pests and fire damage and operating as an air barrier while allowing potentially damaging water vapor to escape. We prefer lime plaster exteriors and either lime of clay interior plasters instead of cement stucco. Cement stucco permeates water vapor more slowly increasing the potential for moisture damage. Cement production is also very energy intensive and emits a high level of CO2 to the atmosphere. Lime produces CO2 in its production but reabsorbs it during carbonation in its application.

Moisture damage is the greatest concern when designing and building any type of structure in our climate. Properly designed and built bale walls have the same general degree of risk to moisture damage as well crafted conventional stick built construction if you design bale walls appropriately. Bale walls generally have more limitations than conventional methods that need to be understood and respected. Building a bale wall well takes care, attention and experience.


STICK BUILT ENCLOSURES

While straw bales are our preferred insulation choice, they aren't ideal for every situation. We've found cellulose insulation to be an excellent alternative and have used it in floors and roofs, and between floors if sound deadening is desired. Mineral wool is another good choice with excellent performance characteristics that works well in light framed walls around the exterior of a timber frame or in the roof framing..

With the timber framing doing the heavy lifting stick frame walls can be built with smaller headers and the use of advanced framing techniques can reduce framing while providing an insulation cavity and nailing for interior and exterior finishes. Some special considerations need to be made for the installation sequencing of the air barrier, electrical and insulation when enclosing a timber frame with stick framing.