How to build Straw Bale Houses | Pros and Cons

June 17, 2022

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5 min read

The construction industry has witnessed a surge in the popularity of alternative building methods, such as ICF (Insulated Concrete Forms), earthbag homes, shipping containers, and earthships. One method that has been gaining increasing interest is building with straw bales.

How Straw Bale is Made

Before delving into the pros and cons, let’s understand what straw bale construction entails. Straw bales are made from the byproduct of agricultural crops like wheat, oats, rice, and barley. After harvesting the grains, the dry stalks are compacted and tied into bales. These bales have been used for thousands of years to reinforce mud structures and thatched roofs. With modern-day challenges like rising building material costs and the demand for sustainable, low-carbon alternatives, straw bale construction is making a resurgence.

Construction Process

The construction of a straw bale home is fairly easy and straightforward. It starts with a concrete foundation and wood sill plates. The bales need to be raised several inches off the ground so that they don’t soak up moisture from the ground. This is accomplished with platforms made of lumber and gravel attached to the concrete foundation. Straw bales are placed on the platform and wedged between the sill plates. They are stacked in running bond courses to form the walls of the house. They can be anchored together with wood, bamboo, or rebar stakes so they don’t fall over during construction. Once complete, the walls can be secured with a wire mesh. A moisture barrier is then applied to the surface of the walls. This can be made of plaster, stucco, cement or clay.

The Importance of a Final Plaster Layer

The final plaster layer is very important because it serves multiple purposes. It acts like a water barrier, an air barrier and a vapor control layer. Areas that receive a lot of rain should consider using rainscreen sidings of wood, brick or stone over the straw bales.

Advantages

Readily Available and Cost-Effective: Straw is abundant worldwide, and materials like sand, clay, and mortar can easily be found at building supply stores. This makes straw bale construction cost-effective compared to more engineered options, though factors like plaster, framing systems, lumber, and mesh need to be considered.
Excellent Insulation Properties: Properly designed straw bale walls can be great insulators, with an average R-value of 2 per inch. This results in impressive thermal performance, reducing energy consumption and enhancing comfort. Additionally, straw bale walls offer minimal thermal bridging, ensuring better energy efficiency.
Fire Resistance: Contrary to common perception, dried straw walls covered with plaster or stucco are naturally fire-retardant. They have three times the fire resistance of traditional walls, making them suitable for regions prone to wildfires.
Healthy Indoor Air Quality: Vapor-permeable finishes like lime plaster allow moisture to pass through walls, preventing condensation issues. Furthermore, straw bale materials are inert and non-toxic, provided natural plasters and straw free from fertilizers and insecticides are used.
Environmental Benefits: Straw bale homes contribute to environmental sustainability by having low embodied energy compared to traditional homes. Straw’s rapid renewability and biodegradability make it an eco-friendly choice, potentially repurposing the millions of tons of straw wasted annually.
Prefabricated Straw Bale Panels: Advanced prefabricated straw bale panels, such as those produced by EcoCocon, have revolutionized the construction process. These compressed straw panels in wooden frames can be factory-made, reducing manual labor and simplifying on-site assembly.
Longevity and Durability: Straw bale homes can have a long lifespan, as evidenced by century-old structures that have withstood harsh conditions without significant rot. Modern examples have even survived wildfires with minimal damage, showcasing their robustness

Disadvantages

High Labor Costs: While straw bale construction materials may be cost-effective, labor expenses can offset these savings. Plastering straw bale walls can be labor-intensive, making the overall building process comparable in cost to conventional methods.
Skill and Training Required: Building straw bale walls requires specialized skills, particularly in the proper mixing, application, curing, and finishing of materials. Training or workshops may be necessary for those planning to construct their own straw bale home.
Space Requirements: Straw bale walls are significantly thicker than traditional walls, leading to reduced interior square footage. This must be taken into account during the design phase.
Permitting and Funding Challenges: Some building codes and regulations may restrict or limit the use of straw bale homes, making the permitting process complicated. Additionally, obtaining funding and insurance coverage might be difficult due to perceived experimental or risky nature.
Pests and Moisture Concerns: Straw bale homes lack studs, which can complicate hanging shelves and decorations. Additionally, straw’s vulnerability to moisture can cause decay and weakening if proper sealing is not maintained during construction.

Conclusion

Straw bale construction is an eco-friendly and energy-efficient alternative to traditional building methods. While it offers numerous advantages, including cost-effectiveness, excellent insulation, fire resistance, and sustainability, it does come with challenges such as labor costs, permitting difficulties, and potential pest and moisture issues. Nevertheless, with advancements like prefabricated straw bale panels, this innovative construction method is steadily gaining popularity as an eco-conscious choice for building a sustainable future.

When I started researching this building technique, I thought it was a crazy idea, but I’ve been converted. Be sure to check out my podcast with Chris Magwood to learn more about the Endeavor Center.