In today's sustainable home building market there are many catch phrases floating around. One of the most heard is alternative building methods. It’s a bit of a misnomer as many of these building methods and technologies are very old and considered traditional in many parts of the world. Whether its straw bales, cob, rammed earth, or any other technique that we will discuss, the knowledge has been preserved and is available for the eco-conscious home owner.
In this article, we will help you decide if straw bale construction is right for your next home.
Straw bale construction has existed for centuries in many agricultural regions where wheat, rice, rye and other grains are grown. It remains a common construction approach in Africa. The bales are created from the waste products of these grains.
In the US, straw bale construction gained popularity in Nebraska as an alternative to sod houses. Straw bale homes were able to withstand the harsh winters much better than the traditional sod homes that settlers otherwise built. The mechanical hay baler, invented in the mid 1800s made this building technique very popular and it spread westward with those seeking to settle in this 'new world'.
During the building boom of the 1950s, mass produced building materials pushed aside this traditional building method, which would become almost extinct for nearly 20 years. Among the traditional building methods that carry the moniker of alternative building methods, straw bale has seen the most resurgence in the US, especially in the arid Southwest.
There are two main ways to build with straw bales today, load bearing and framed or non-load bearing. Due to instability in high winds, load bearing straw bale homes have been much slower in finding approval from zoning boards and inspectors. The more common strategy is the use of a post and beam structure and straw bales as infill or insulation.
In either strategy the bales are stacked in running bond layers and often “skewered” with steel rods or strapped to the foundation to create walls the behave like a solid wall. All bales are stacked on top of either concrete or stone foundations that help to prevent moisture seepage from the soil. Moisture is the biggest enemy of straw bales and during construction, the bales must be protected.
The moisture protection extends into the life of the structure as well. Unless the region is extremely arid, the walls are kept breathable to avoid moisture build-up and eventual rot. This requires the use of a non-cement based stucco or plaster applied either directly over the bales or over a wire mesh applied to the surface of the bales. The finished walls often have a very textured feel and warmth.
The Ups and Downs:
The major advantages of using straw bales are the high insulation value, lower cost and availability of straw bales in many locations. Straw is also a renewable resource and in many cases a waste stream product. In addition to the low cost, straw bale construction can be completed by unskilled labor, putting it in the realm of DIY projects. With any technique that is unfamiliar, we do advise that anyone wanting to build with straw bales start off working with someone with experience with this material.
The major disadvantages of straw bale construction are rot and infestation. Rot is the result of improper moisture control. In arid regions, moisture isn't much of a concern but in northern climates, special attention should be paid to controlling moisture seepage and infiltration and also removing moisture from the walls. Proper exterior surfacing can go a long way toward handling moisture and also helps reduce the risk of rodent and insect infestations. Other disadvantages include the instability of load bearing straw bale construction in northern and windy climates, some flammability concerns and the thickness of straw bale construction.
If a design is approached with straw bales in mind, all of the disadvantages can be overcome. From designing for twelve to eighteen inch thick walls to using pre-compacted high strength bales, a straw bale home can be built almost anywhere. Straw bales homes are a great way to create a unique home that is both comfortable and sustainable.