[DJC]

[design '98]

Removing the barriers to bales

By MICHELLE QUESADA
Michelle Quesada, Architects

When Kate Calvery came to me in early 1996 and asked me to design a straw bale house for her on Vashon Island, my heart sank.

I had attempted to permit a straw bale house a few years before in King County. The county said: If the International Conference of Building Officials approves it, okay. ICBO said: If you have all the testing done, then okay.

UW straw bale house

This "house" built at the University of Washington has passed several rigorous tests for safety.


That client gave up. Few homeowners can afford the thousands of dollars it would take to undergo testing for flame spread, lateral capabilities, long term stability, moisture content and insulation.

But Kate was undaunted. She was intrigued with the beautiful adobe-like aesthetic bales offered and both Kate and I believe very strongly in sustainable building practices.

A century-old trend

Why straw bale, you ask, in our maritime climate with all the traditional building products available? Good question.

Straw bale houses are solid, sturdy, quiet and beautiful, evoking the esthetics of traditional building types such as rammed earth or adobe. This form of construction bypasses many industrial processes and puts the products of local agriculture directly into housing. In the United States alone, some 200 million tons of straw are burned every year.

Straw bale houses offer extremely high insulation value, and a range of tests has shown that properly constructed straw bale walls withstand fire and earthquakes very well.

The best test is time. People have been using straw in building since early times in Asia and Europe.

In this country, the history of straw bale structures seems to have begun in Nebraska. Once horse-and-steam-powered balers showed up on the prairie, the oversized building blocks made temporary homes and storage shelters. Some of these structures were plastered and trimmed out. Still in use today are some straw bale homes and structures built at the turn of the century and in the 20s. The straw is still in excellent condition. The term "Nebraska style" stems from these structures, in which straw bale walls actually support the roof loads.

More recently, straw bale homes have been built in the Southwest. Grassroots organizations got the word out that here was a material that was essentially an agricultural waste product with excellent insulation value. It was relatively cheap to buy and, with a simple design, cheap to build.

A successful experiment

Smaller jurisdictions here in Washington have been permitting straw bale structures for some time. King County, however, has not.

I approached the county once again with my best how-can-we-work-together attitude. When King County agreed to work with us, we were overjoyed.

Not that there wasn't a mile of hurdles to jump. Their proposal was this: we find someone to do some testing - say, the University of Washington - and help define methods of building and inspection. Then they would grant us the permit.

It took several months to find the right person at the U.W. David Riley, an assistant professor in the Department of Building Construction, was our man. He had an interest in exploring how new materials can be accepted into the codes and was eager to do structural testing. He very quickly secured a grant and agreed to shepherd a small experimental structure to be built behind Gould Hall.

The structure, a shed which would be later moved to the client's property, would serve as the prototype for the future house. Details and methods of construction were discussed with officials from the county.

Everyone, of course, was concerned about water penetration.

I decided to design the shed as a post-and-beam structure, with straw serving as infill.

As it was built, details were inspected and approved. Dave wired moisture sensors into strategic places. Data from the sensors feed directly into a computer.

Results have indicated that the bales are well below the maximum 19 percent moisture content. Above this, the possibility of microbial activity exists - that is, they may rot. Data will continue to be collected for the next couple of years.


This form of construction bypasses many industrial processes and puts the products of local agriculture directly into housing.


In the spirit of sustainability, lumber used was from TrusJoist MacMillan's Frame-Works Building System. These products provide an alternative to solid wood framing. Doors, windows and the fan all were purchased at Second Use, a resource for used building products.

David also orchestrated lateral tests with walls that mimicked the structure of the shed and future house. Testing was made possible with grants from King County and the University of Washington. The preliminary results seem to indicate that this type of construction can perform quite well under lateral loading.

Tests were performed under conditions that approximate the test conditions for typical plywood shear investigations. The test regimen included both static and dynamic testing. The results seem to indicate that this type of wall will have significant resistance to wind and seismic loading and the type of failure is more ductile than brittle, which is desirable under earthquake loading. In other words, even after the walls have failed structurally, the walls and the plaster remained intact.

The permit was signed off last month.

There is great relief throughout the straw bale building community. The permit is the result of the cumulative effort of so many people - from experts in Arizona to a friend in Alaska who shared his experiences building his own home. Not only will others be able to build with bales in King County, but the knowledge gained from the moisture testing and structural testing of David's team at the university will be beneficial to the entire straw bale community.

In addition to myself, the team for the experimental shed includes: Nic Rossouw, Swenson Say Faget, structural engineering; David Riley, University of Washington, testing and coordination; Andy Green, AD Green Construc-tion, general contracting.

Goods and expertise were donated by McGlynn Plast-ering, Inc., (interior and exterior plaster); TrusJoist Mac-Millan, (studs, joists, and beams); David Riley, University of Washington, (grantwriting, testing, coordination); Stafford Architects, (expertise, tools); Chris Ricketts, Bernard Moore and William Walker of King County, (expertise, open minds); Mark Fowler of Northwest Wall and Ceiling Bureau, (expertise); and the departments of Construction Management and Civil Engineering at the University of Washington.


Michelle Quesada is an architect specializing in commercial and residential design. She works with private and publc clients.

Return to design '98 top page

Copyright © 1998 Seattle Daily Journal of Commerce.