FIRE TESTING STRAW BALE WALLS
I received an email today from Bill Christensen, the proprietor of GreenBuilder.com. It holds some very exciting news on recent fire testing of straw bale wall assemblies. Of course, those of us building straw bale houses have known that they are extremely resistant to fire; however, now we have proof to back it up! Here is what Bill had to say:
“It’s my pleasure to announce that plastered straw bale walls have just passed two important fire tests.
Two walls were constructed at a building materials testing lab in San Antonio earlier this summer – one was built with poly-tied bales on edge and covered with two coats of hand-troweled cement/lime plaster over stucco mesh, intended to approximate an infill wall in a commercial or institutional (or residential) setting. The second wall was stacked flat, put under 600 pound per linear foot load, and shot with two coats of clay plaster, approximating load bearing residential construction. No mesh was used on this wall.
The cement/lime plastered wall easily passed the ASTM E-119 2-hour fire and hose stream test. Lab personnel told us they felt it probably would have made another hour easily.
Due to some cracking on the exterior (non-fire) side of the clay plastered wall which occurred while moving the wall up to the furnace, and having seen the fire side plaster on the cement/lime wall basically being held on only by the wire mesh for the majority of the second hour, and considering that a 2 hour rating is rarely required for residential construction, we chose to do the clay plastered wall for just a one hour test. It too passed.
The official test reports will be available in about two weeks on the www.ecobuildnetwork.org and www.DCAT.net websites. They will also be included in the appendix of Bruce King’s forthcoming book, ‘Design of Plastered Straw Bale Structures’ (due out in time for the ISBBC in Ontario in late September).
Next time some insurance company gives you a hard time about straw bale being a fire hazard, you have an answer for them.
Congrats to the team: Bruce King, David Eisenberg, Matts Myrhman, Ben Obregon, Frank Meyer, Kindra Welsh, Baron Cougar, Mike Atkinson, Paul Taylor, and yours truly.
Thanks also to CASBA, COSBA, SBAT, and the individual donors for their financial contributions, as well as to whatever foundation it was that Bruce King managed to get the grant from.”