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Strawbale is about energy efficiency – an insulation value averaging R-30. And it likes to have its face to the sun and its back to the wind for warmth and protection like all buildings do.

Strawbale is about structure – bales used to bear the load of the roof (and the snow), or simply used as infill for insulation within another type of structural system: timberframe, post-and-beam and modified post-and-beam including box columns.

Strawbale is about form – it can be shaped in many ways – square, rectangle, circle, domed vault, conical, hexagonal, octagonal, polygon. It can be one-story or more (a five-story straw-bale wall panel system has been used in The Netherlands).

Strawbale is about flexibility, accessibility and adaptability of interiors designed to meet the needs of all occupants over time; interiors with good air flow, natural ventilation and proper venting of air and moisture.

Strawbale isn’t just about its structure and form – it’s about how it feels. Cozy, comfortable, natural, encapsulating you within its thick walls – 14- to 16- to 18-inches thick – giving you a sense of security. No big bad wolf is going to blow this structure down – strawbale has been tested to endure 100 mph winds – and has a burn rate of one to two hours (dense bales have little oxygen to feed fire).

Strawbale isn’t just about building – it’s a value-added market for the grower. Straw bales for building can be made from wheat, oats, rye, rice, hemp, prairie grasses (without forbs) – but not woody, brittle stemmed plants such as alfalfa and other feedstock. Buildable bales should be free of weeds and seed heads; dry with no sign of moisture, dirt, mud, or any contaminants. Bales should be bright and clean, dense and well compacted, trimmed on all sides before stacking to avoid filling voids and holes, and should be handled so that they remain in good condition

Strawbale is about healthy interior environments free of toxins - and placing the structure on a piece of site with little harm done to the land and vegetation.

Strawbale buildings are long-lasting when they have good hats and boots – a sturdy hip roof with wide eaves to protect the walls and take the water away from the sides and surroundings, and a solid foundation wide enough and deep enough to support the loads.

Strawbale can be easy to build depending on the design and other factors by people of any age. It can be economical or custom designed. It can be creative and artistic, innovative and expandable.

Straw-bale buildings can be insured, funded the same as any other building, pass codes, have resale value.

Straw-bale building has been done for centuries and its durability has stood the test of time.

Joyce is a consultant on design and construction, teaches classroom seminars and at hands-on workshops, and is managing editor of The Last Straw, the international journal of strawbale and natural building. For more information, contact Joyce Coppinger, ReBuild Associates, Lincoln, Nebraska, 402.483.5135, and visit www.thelaststraw.org and the TLS blog at http://thelaststrawblog.org.

by Joyce Coppinger, Managing Editor/Publisher, The Last Straw Journal

Wall Structures
The structural methods used for the design and construction of bale walls are generally of two types: loadbearing and non-loadbearing. Stated another way – bales supporting the weight of the roof and any snow or other roof loads, and any post-and-beam or modified post-and-beam structure with the bales used as infill for insulation only.

Timberframe is the post-and-beam structure of choice in most countries. Posts of conventional milled 4×4, 4×6 and 6×6 wood; lodge poles, timber bamboo and other types of materials have been used. Modified post-and-beam structures are wide-ranging and diverse – anything from box columns to ladder-truss wall systems, to the current experiments in and development of SIP or structural insulated wall systems (also called wall panel systems or panelized walls) using bales as the insulation material rather than rigid foam insulation as the material sandwiched between the sheathing on both sides. [See articles in TLS#42 and #55.]

Widths
Bale walls come in many different widths depending on the size of bales you use, how you lay the bales as you stack them, and even the type of material baled and the method used to stack the bales to form the wall.

Widths Using Small Square Bales: Typical widths for bale walls are 16 or 18 inches when the bales are laid flat (strings or wires on the top of the bale). If stacked on edge, the bale width will be 14 inches with the strings or wires on the side of the bale. If the bale is stood on end to fill a framed space, the bale can be either 14, 16 or 18 inches depending on the size of the bale and the direction in which you set the bale.

Size of Bales
Even though a bale may be called “square,” it’s usually rectangular in shape.

The size of a small square bale may vary by region or country depending on the type of baling equipment used or the method of making the bale, e.g., bale press or hand pressed compared to using a mechanical baler. The bale may also vary because of the type of mechanical baler used and how it’s set to produce a bale.

The small and medium size balers used in some regions of the U.S. have a fixed bale chamber that produces a bale that is 14-in.x16-in., 14-in.x18-in. or 16-in.x18-in. The length can be varied to produce bales between 36 inches and 41 to 48 inches. This is the range of length that is required by most automatic bale wagons used to pick up bales in the field in the U.S..

You should also be aware that there are also other sizes of bales used – some are called “jumbo” bales because of their large size. In some places, these large bales might be called 4x4s or 6x6s or 8x8s. Some people define a square bale’s size as small, medium and large. Small bales can be 24in.x24in.x48-in. Or they can be 14-in.x 16 to 18 in.x 36 to 48 in. A medium bale of this type is around 4-ft.x4-ft.x6-ft., and large bales around 6-ft. to 8-ft. square by 8-ft. to 10-ft. long. Weight depends on the type of hay and settings of the baling equipment.

And density (compactness of the baled material) or compression (how much pressure is placed on the bales to “compress” them when they are created or after they are stacked) of the bales might also change the dimensions.

The binding material on the bales is most often wire or poly twine; sisal (natural fiber) isn’t the best to use as it tends to break while the bales are being handled. Some people don’t use wire as they are concerned about moisture might condense on it or be drawn to it; some feel it’s difficult to work with when retying bales, others feel it’s easier. Some don’t like to use the poly twine because of the coating or because they feel it’s not as easy to work with. In most cases ot comes down to personal preference or type of binding available locally.

Placement of Bales
Bales laid flat are usually 16 to 18 inches wide and 14 inches high; they can be 36 to 40 to 48 inches long. Bales stacked on edge are usually 14 inches wide, 16 to 18 inches high, and the same lengths as mentioned for bales laid flat. Bales used to fill in framed spaces – or stacked on end – can be 14, 16 or 18 inches wide depending on how you orient the bale in the space filled.

There has been and continues to be much discussion about the way bales are laid or positioned when stacked. Are bales set on edge or bales laid flat easier to plaster, and what reasons do balers use to explain a preference for one method or the other? Do the bales laid flat have less or ore insulation value – and why?  Do bales set on edge have more tensile strength than bales laid flat?

What to Use and What Not to Use
A bale made with a mechanical baler that chops the straw as the bales are made probably doesn’t produce the best bale for construction – it tends to fall apart or could be harder to work with when cutting and tying.

A bale made from alfalfa will be hard to use – the alfalfa tends to be woody and brittle, the bales are usually not uniform in shape and perhaps even in size to some extent. This may be true of bales made from switchgrass or flax or other “slippery” materials.

Bales made from tumbleweeds are not suitable for bale building – they are very brittle and highly flammable (usually very dry). The same could be said for pine straw bales – the kerosene in the pine needles is flammable and the pine needles are also one of those “slippery” materials mentioned earlier.

The most common materials used for buildable bales are wheat, oats, rye, rice, and hemp. It’s said that the Nebraska prairie pioneers used prairie meadow hay (probably hard to find these days), cattails and wetland reeds (most often baled during droughts). We’ve heard of the use of bales made with timothy grass, Sudan grass, and barley. We’ve been asked about corn stover and soybean stover – but don’t know of anyone who’s ever used this crop residue as a bale building material. If you’ve heard of other materials used for buildable bales, please let TLS know.

No, this is not the house. We don't have a picture of a bale house on fire!

This story is a reluctant one about a house comprised of both wood-framed and straw bale walls lost to a fire. The structure was built over a longer period of time than most main-stream homes.  The different phases incorporated the most appropriate materials at the time for the owners. We are excluding specific reference to the owners and the location of the building due to privacy concerns. For this article we will say that the building is in the central U.S. at approximately 8000 ft elevation and the Owner’s name is Bob. In the end, it really does not matter who owns the home or exactly where it is. What we will focus on is the performance of the bale walls in the fire, the aftermath, and how the owners and insurance company feel about the whole incident.

The building was an un-permitted residence in a rural mountainous area. As mentioned above, some of the walls were wood-framed, others were built with bales. The bale portion of the structure was round, approximately 26′ in diameter, on a foundation that was an 8″x18″ concrete grade-beam supported by concrete pillars, with a yurt-style roof which included a “tension-ring” cable. The bale walls were Nebraska-Style (no posts) and had a 2×6 box-beam for the top plate with plywood on the bottom but not the top. The box-beam was filled with rigid foam insulation. Both the interior and exterior surfaces of the bale walls were covered with cement-based plaster. Two coats were present on the exterior and one coat was completed on the interior. There were relatively small areas not plastered on the interior, but the location of these un-plastered areas were not specified in my conversation with Bob.

The fire was started in the crawl-space of the framed portion of the structure by accident. It quickly spread throughout the framed structure and overtook the occupants who had to flee for their safety.  Bob is a local volunteer firefighter who was overcome with smoke inhalation and had to be taken away for medical care. He was present for a majority of the fire and taken away before it was extinguished. However, he has some interesting comments regarding the bale walls, how they performed and how they were affected by the fire. The family lost everything to the fire and is now picking through the remains.

The fire quickly engulfed all of the wood-framed structure and spread to the floor and then the roof of the round bale structure. The roof of the round structure collapsed inside the bale walls but the bale walls themselves were still standing when the fire department , hampered by by the long driveway and 18″ of fresh snow, arrived on the scene 50 minutes after the fire started.   Due to smoldering straw the fire department felt compelled to knock the bale walls down to access smoldering area within the walls.  Eventually all the bale walls were knocked down and all of the smoldering extinguished. This process took five days after the initial incident.

Bob commented about how fast the areas with no plaster ignited compared to the bale walls covered with plaster. The windows and doors had been framed using standard wood bucks. These, in addition to the wood box-beam, became the main avenues for the fire to spread into the bale walls. It appeared that the fire moved down from the top and in from the window and door bucks. Had these areas been plastered, or concrete bucks used, Bob feels the bale walls may have been spared.

Due to the generally impenetrable nature of the walls they seemed to act as barriers to heat-flow in both beneficial and detrimental ways.  Bob had installed his solar PV array 10 feet from the bale structure. The PV panels were virtually unharmed due to the shielding nature of the bale walls. His wood-framed shop, situated approximately 30 feet from the framed portion of the residence, ended up burning to the ground from direct exposure to the heat of the fire. The drawback was that Bob felt the bale walls created an oven-like effect within the building, holding heat inside, keeping the temperature very high.  As a result, one of the losses was the family safe which was supposedly fire-proof.  It was unable to withstand the “heat-trap” surrounded and created by the bale walls.  From these accounts, It is clear that the bale walls have a very significant heat-shielding effect during a major fire event.

The entire structure was insured by Allstate Insurance.  Bob was honest with them at the time of insuring the building and did not hide the fact that part of the building incorporated bale walls.  Allstate did not seem to make a big deal of the fact either then or now.  It appears they are making a pay-out on the insurance policy.  This is good news to bale building owners everywhere.  An insurance company had the capacity to not focus on the fact that some of the exterior walls were made of straw and plaster.  It is not clear if they understood how stable the walls were during the fire since they did not collapse, like the rest of the structure.  The fact that the bale walls did not contribute to serious problems was probably one reason for the lack of focus.

Being a volunteer firefighter Bob was frustrated he could not help fight the fire that destroyed his own home.  He understood that following orders from his fellow firefighters to seek help for his smoke inhalation was the right thing to do.  When asked about how the fire was suppressed in the bale walls and why it took so long, it became clear that the ongoing smoldering was not going to stop on it’s own.  The walls needed to be broken up in order to access all of the smoldering spots.

It seems that there is a pattern among bale buildings that are engulfed by flames.  The walls remain standing as long as anyone is willing to let them stand.  The main reason they are taken down is to gain access to smoldering areas within the walls so as to eliminate any risk of spread and the accidental ignition of other fires elsewhere.  The fact that bale walls are very effective heat shields makes them good fire-separation wall candidates between living units, or uses, within a structure.  They remain stable throughout the fire event, which cannot be said of steel or wood-framed walls in low-rise residential or commercial construction.  The fact that they tend to smolder and require maintenance for days after the initial fire event costs money and resources, but weighed against the fact that they do not fail catastrophically means that they may be considered as life-safety elements in buildings with many uses and occupancies.

The lessons learned in this building are that bale walls are incredibly stable during a fire event, offer a thick shield to retard flame-spread, and are tough to dismantle, requiring many days and resources by the local fire department.  When put together it seems that the bale walls themselves had a much better track record than any other part of the structure.  Feel free to comment or add to the discussion by logging in and submitting your thoughts.

Bob says he will not rebuild with bales mainly due to the huge amount of labor involved.  He will probably choose to build with some form of ICF (insulated concrete form) and steel.  He and his family enjoyed their bale home, but the time and labor necessary do not seem as realistic the second time around.

All fires in bale buildings are felt throughout the community as a serious and deep loss.  Even though we do not wish for them there is a great deal to learn from each and every one.  We hope this account will help firefighters, insurers, designers and homeowners make the best decisions possible.  Please comment below and participate in the conversation.  We are interested in your thoughts.  Email the author with any specific question for the owner offline.

One of the main reasons for creating this forum is to bring the content of TLS in to real-time so we can discuss what has been written.  We encourage comments even with graphics such as CAD drawings or pictures, or maybe even a video, if it helps get your point across.

If the information you find here is useful, just think what you will find in the print and pdf versions of the publication when you subscribe.  Back issues can also be ordered at The Last Straw website here.

As some of you may know, The Last Straw has fallen behind in it’s publication schedule. The quickest way to make issues available as they are published in the coming weeks and months is to post them in PDF format to the online ordering system on the TLS web site. If you want to switch over to PDFs for your subscription, just contact Joyce at <thelaststraw@thelaststraw.org>.  As of this writing TLS#59 is available in PDF format through the TLS online order system. The print version will be published and mailed as soon as possible. The TLS Team is working on #60. The TLS Editor is working on content for #61/Women in Strawbale and Natural Building, #62/Putting a Project Together, and #63/Commercial and Industrial Buildings of strawbale and natural materials.  We are trying very hard to catch up with the backlog and apologize for the delay.

Thank you for visiting. Feel free to look around.  We hope to see you back here often.  Happy baling!

Questions or suggestions can be directed to admin@thelaststrawblog.org.