Straw Bale Testing

Structural and fire tests were done by SHB AGRA, Inc., a certified testing company in Albuquerque, New Mexico. Straw-bale wall sections were tested both with and without stucco coatings. Transverse load testing (ASTM E-330 ), which simulates wind pressure on walls, found significant deflection of the unstuccoed straw-bale wall (up to 1.87 inches) at transverse loading of 20 pounds per square foot (psf), but very little deflection with the stuccoed wall (maximum deflection of 0.13 inches at 20 psf, and 0.22 inches at 50 psf).

Fire tests (ASTM E-119) showed that the unstuccoed wall survived flame penetration for 34 minutes and met the requirements of most residential building codes. The stuccoed straw bale resisted flame penetration for 120 minutes, at which time the test was discontinued. During that period, while temperatures in the furnace exceeded 1,900°F, temperatures on the outside of the wall only got as high as 63°F. At the conclusion of the test, the stuccoed straw-bale wall was blasted with a 21⁄2" fire hose, and there was “no indication of distress or failure.” Even with the unstuccoed straw-bale wall, an examination of the straw after the test showed that it “burned slowly, and the charred material tended to remain in place. The residual charred material appeared to protect the underlying straw from heat and ventilation, thereby delaying combustion.”