What is straw and what is a bale?

Straw is the dry stems of cereal grain left after the seed heads have been removed.

Some Examples of Straw

• Wheat
• Rice
• Rye
• Barley
• Oat
• And similar plants

Because straw is usually locally available it is viewed as a readily available material. Straw bale building is the most popular natural building technique in practice today.

When designed for green living, a straw bale home is one of the most comfortable and efficient style of homes available today.

Some folks even host old-fashioned bale-raising parties to get their walls up. Could there be one I your future?

What is a bale?

A bale is a rectangular compressed block of straw bound by string or wire.

What Makes a Correct Bale?

A bale must meet the following criteria:

• Dry density of 7.0 pounds per cubic foot

• Rectangular compressed block of straw with a minimum thickness of 14 inches

• Moisture content shall not exceed 20 percent.

• Bales shall be bound with ties of either polypropylene string or baling wire

Why build with Straw bales?

Straw is an abundant renewable resource.

It’s the dry stems of cereal grain left after the harvesting of the seed heads. You know all those cereal boxes on the grocer’s shelf? There are over 200 million tons of waste straw processed each year in the U.S. alone! And most of it is burnt, sending billowing clouds of smoke up into our air.

Constructing a typical house requires more than an acre of trees, and generates four pounds of construction waste per square foot. That is why, when you build with straw bales, not only you save our frosts but also, you improve the quality or the air we all breath.

Energy Efficient and Quiet

RENEWABLE BUILDING MATERIAL – instead of using petroleum based insulation products, the home is built from a renewable resource - straw.

This method of building is now promoted by the federal government (http://www.energy.gov/)

A home constructed out of straw bales can lower your energy bills by up to 75%!

The thick bale walls eliminate almost all unwanted outside noise. Conventional homes do little to block noise.

• Beauty

• Health

• Building with the waste product of our farms keeps the air clean.

• Natural building materials allow you to breathe easy in your home. Straw bale offers an alternative to “Sick House Syndrome.” New homes today are polluted with chemicals from building materials that create allergies, asthma, ill health and fatigue. Using natural materials eliminates this problem.

• Beauty of natural colors, and the bales have also been found to be pest resistant. Another advantage is the ease of creating beautiful, curved, sculptural walls. The naturally thick sheltering walls offer a sense of protection and sanctuary from the outside world that conventional homes often do not.

Fire resistance

• Increased fire resistance

• Conventional construction offers only a 20 minute burn resistance.

• Because of the density of the bales and the thick plaster, bale walls yield a 60 minute burn resistance

The Truth Behind the Myths about Straw bale construction

The big bad wolf.
Do not worry, your building will be engineered for wind, seismic, vertical loads and the big bad wolf.

Straw will rot in the walls.
Not if building is designed and drained correctly.

Straw will catch on fire way too easily.
Like a telephone book, condensed packed straw will not catch fire due to lack of air/oxygen. In addition, it will be covered with fire resistance stucco.

It will grow mold.
As long as the house is designed and drained correctly, no worry about mold. There is a house that has been standing for hundreds of years and doing very well.

It will smell like a barn in my house.
No way. Straw bales is natural material and you will not get the gas released from manufactured items.

It is cheaper to build with bales.
Straw bale construction is about 15 % more than traditional stick framing construction. However, if you do the work yourself, it could be cheaper.

Is there a Building Code for Straw bale construction?

• Yes it is included a a spcial section at the end of Some Codes such as Appendix R of the Oregon Residential Specialty Code

• Please check with your local building Department

Types of Straw Bale Construction

There are 2 types of straw bale homes-

1. Load bearing

Limitations:
Height: One Story with height to width ratio of 5.6 to 1.
Openings shall not exceed 50% of the total wall area

2. Non-load bearing

The difference between the two is that in the load-bearing style, the stacked bales support all or part of the roof. Non-load-bearing homes are limited to one-story. Load-bearing styles, aka, infill design, is constructed so the bales are stacked within a structural framework, such as steel, wood, etc. These buildings can be more than one-story.

How do Straw bale building resist Wind and Seismic forces?

There are several ways that a straw bale building resist lateral forces

• Straw bale wall assembly with reinforced plaster skin

• Diagonal Bracing System

• Engineered Frame

• Hybrid System

A combination of the reinforced plaster skins and the engineered brace frames produces a strong structure that is easy to frame, bale and plaster.

Resources and Links

For samples please visit our Residential page.

For More information about straw bale constructions, please visit: www.StrawBale.com

“We have no choice
but to go green.”

Nabil Taha, Ph. D., S.E.
President
Precision Structural Engineering