Architecture, Sustainable Practice
Straw Bale Construction FAQ
Have you ever heard of straw bale construction? It’s a form of building construction where bales of straw are stacked within a timber frame to insulate the walls. Not only is this a sustainable building method, it’s just plain cool. If you’e curious to know more, check out these frequently asked questions.
March 21, 2024
We get a lot of questions about straw bale construction. We sometimes joke that folks are “bit by the bale bug.”
Despite being a less-known building system in the USA, it remains a popular option for folks interested in alternative building practices to help them meet their sustainability goals.
Here, we’ve compiled a list of frequently asked questions to get you started if you’re considering straw bale construction for your project.
What is so good about straw bale building?
Where do we begin? There are many advantages to straw bale building.
Straw bales offer excellent insulation, over twice as much as a standard stick-framed house. This saves energy, which saves money, and is kinder to the environment.
They’re also simple to build with, making them the perfect material for owner-builders and community groups. With a “barn-raising” type party, walls for a single-family home often will go up in one day.
A straw bale home is beautiful and sculptural. The thick walls create wide window sills, and are easy to carve into niches and curves.
Additionally, straw is a non-toxic, natural material which means healthier indoor air. A house built with straw bales typically uses less lumber, reducing the impact on our forests.
Straw is annually renewable and abundant wherever grain crops are grown, and is in fact often burned as a waste product. Baling the straw for construction can reduce air pollution, and provide local farmers with additional income.
Straw bales create such soundproof walls, one Nebraska pioneer family was found playing cards in their kitchen, oblivious to the tornado blowing through town!
How is a straw bale building constructed?
There are two main types of wall systems. Nebraska style and in-fill wall systems. More recently, prefab options have also become available.
Nebraska Style
Originally, in turn of the 20th century homes on the northern plains, bales were used as the structural system. Many of these buildings are in good condition today, and the method is still used for buildings of small to moderate size.
Dry, dense bales are stacked like big bricks, and pinned with rebar or bamboo. The roof then rests on a wood plate system at the top of the wall, which is secured to the foundation. This type of load-bearing construction is often termed Nebraska Style due to its place of origin.
In-Fill Wall Systems
In addition to Nebraska style, another method is often used. A simple frame of posts and beams carry the structural load of the building, while the bales act as walls and insulation. The bales are stacked in the same way as the load-bearing option, but placed either inside, outside, or in between the posts.
These are termed in-fill wall systems. They are usually easier to permit, since building officials are familiar with how a frame reacts to different loading conditions, and they can allow more design flexibility. It’s also nice to have the roof up before the bales to protect everything from the elements.
Prefabricated Options
There are also prefabricated straw wall panels on the market now. As a manufactured product, these are in a different category from bales, but the wall thickness and much of the indoor experience is similar. It is promising to see straw being developed into something that can make an impact on a production housing scale.
Won’t the bales rot?
Liquid moisture can be a problem in any type of wall. Proper detailing at the floor, windows, and roof overhangs will stop liquid moisture from entering the bales. Once a good stucco finish is applied to the outside, some rain hitting the wall is not a problem.
Locations with heavy wind-driven rain will benefit with wood or metal siding over a single coat of stucco. In all cases, it’s important to select a stucco material with proper permeability, so your walls can allow moisture vapor to escape. As long as the bales are kept dry, you should not have any problems with rot or fungi.
Are straw bale buildings more susceptible to fire?
No. In fact, they’re more fire resistant than a typical framed house. Individual straws will burn, but a straw bale is so compressed, there is not enough oxygen for combustion. It is like trying to burn a phone book.
Straw also is high in silica content, causing the surface of the bale to char, and block the flame from reaching farther into the bale. In laboratory tests in New Mexico, a plastered bale wall easily passed a two-hour fire rating, which is required for commercial construction.
Aren’t there problems with mice and insects?
There is no food value to straw, since the seed heads have been removed at grain harvest. No animal or insect will eat it. A mouse might tunnel into a bale wall that is not protected by plaster or stucco, but a mouse could get into a framed wall just as easily if there is a hole in the siding or drywall.
The same is true with insects. If you seal your wall surfaces properly, you should have no problems with pests.
Do straw bale houses cost less to build?
Not necessarily. The wall materials may cost less but bale building can be labor intensive. If you want a typical American house, with all the plumbing and appliances and a contractor to build it, the costs can be a little more than the same home built with other wall materials.
Because of the wall thickness, the foundation and roof will also be larger than a framed house with the same usable space inside. Considering the cost of the wall system in a house is typically about 5 to 7% of the total cost of construction, walls are not the determining factor in your overall budget. Your life-cycle costs, however, could be much less.
This is not to say you must spend the same amount of money on your house as the average homeowner. Bale building got a reputation of costing less due to the many do-it-yourself pioneers who have taken this on as a labor of love. If you have the stamina and desire to act as your own contractor and invest your own sweat and ingenuity, you can save on costs substantially.
Straw bale walls are fun to raise with a group, and the rest is manageable if you keep the project simple. Just be prepared to spend a year or more going from groundbreaking to move-in. We would be happy to connect you to others in our network about options for workshops to train you and others in the specifics of
building with straw bales.
What about getting a permit?
While some cities and many counties in Washington State have straw bale buildings they are proud of, others are more cautious about it. The current Residential Building Code has a chapter on prescriptive straw bale construction, but this code section has not yet been adopted by all jurisdictions in our area.
Current building codes do allow for alternative materials if a licensed architect and engineer are involved in preparing your plans, as their professional stamp of approval transfers liability of the home’s integrity to them. If you are going to build in a jurisdiction that has allowed straw bale construction in the past, it may be easy to get a permit with properly prepared plans (as long as there haven’t been problems that changed their minds).
If this is a new material for your jurisdiction, it may take extra effort to convince the local building official that this alternative material will perform as well as the standard frame construction they have become used to. We’ve gotten the first straw bale homes through the permit process in many jurisdictions, and found that early education and collaboration are key.
We dive into more detail about bringing straw bale construction and other sustainable measures to building codes in the Building Better Codes episode of the Living Shelter Podcast with guests David Eisenberg.
Is there insurance and financing available?
Some insurance groups have insured bale homes at standard rates, while others are more skeptical. You’ll want to shop around and find agents that have historically been supportive.
The same stands true for lenders. You may need a licensed contractor involved in your project to secure a construction loan. The costs of building a home out of alternative materials, such as straw bales, are being incorporated into some cost-estimating books, so well-informed insurers and appraisers can calculate their value.
The missing link for appraisers has been finding local comparable sales, since there are still few of these homes in any geographical area and even fewer that have been sold to new owners. To overcome this some people have listed “wood framed with cellulose insulation” as the wall type on loan documents.
What are the best resources to learn more?
There are many sources of information out there. Three books come to mind most readily.
The Straw Bale House by Steen and Steen is a great place to begin, a good overview with lots of pictures.
Build It With Bales by MacDonald and Myhrman is the definitive owner-builder manual, filled with loads of practical advice, wisdom and humor.
Serious Straw Bale: A Home Construction Guide for All Climates by Paul Lacinski and Michel Bergeron provides the most current information on building practices in many climates.
The Last Straw Journal has long been publishing the latest research and findings from the straw building community at large and now has an active website with regular updates.
There are also quite a few Facebook pages and LinkedIn groups dedicated to straw bale building.
And, of course, we’re always happy to talk about your straw bale project goals! Get up close and personal with some beautiful straw bale homes like our Bainbridge Straw Bale project and Our First Bale House. You might even get “bit by the Bale bug” and become another straw bale advocate!
