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Straw bale house in San Miguel de Allende Mexico © Daniel Friedman at InspectApedia.com Straw Bale House Construction & Inspection Methods

Straw bale constructed homes:

This article describes a straw bale constructed home that is more than twenty years old, commenting on its construction method, durability of straw bale construction, and where straw bale home defects are likely to be observed. Our page top photo shows the exterior of a load-bearing strawbale constructed home in San Miguel de Allende, Mexico.

Straw bale homes are not common in San Miguel, but are popular in many areas of the Southwestern United States.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Straw Bale House Building Construction Defined & Illustrated

Straw bale house © Daniel Friedman at InspectApedia.com

Strawbale construction is a construction method ascribed to early settlers in the United States in Nebraska in the 1890's, and a method popular in the U.S. into the 1940's with a continuing following of straw bale enthusiasts to the present.

Prior to about 1890 straw, hay, and similar grasses were used for thatch roofing but it was the advent of the mechanical bailer using wire or twine and producing rectangular straw bales that permitted straw to be used as construction building blocks.

According to the U.S. DOE,

Straw bales were a fairly common building material in the United States between 1895 and 1940. Interest in straw-bale home construction began to re-emerge in the mid-1970s. But it wasn't until the mid- to late-1990s that building codes began to acknowledge it as a viable approach.

The rising cost of conventional construction materials, techniques, and concern for our environment has fueled the growing popular enthusiasm for straw bale home construction.

There remains much we do not understand about appropriate ways to build with straw bales in different individual building assemblies, climate zones, and weather conditions.

Two of the current straw bale construction methods include non-load-bearing or post-and-beam, which uses a structural framework with straw bale in-fill, and load-bearing or "Nebraska style," which uses the bearing capacity of the stacked bales to support roof loads.

Proposed straw bale structures still face considerable barriers, including the following:

The non-load-bearing construction method is the approach most regulatory authorities accept today.

To find out the building code standards for your state, contact your city or county building code officials. Your state energy office may be able to provide information on energy codes recommended or enforced in your state.

How to Recognize & Assess the Condition of Straw Bale Constructed Buildings

But how easy is it for a home buyer or home inspector to quickly recognize a straw bale built home? A glance at our page top photograph of a straw bale house in San Miguel de Allende, Mexico, may not immediately show how this house was constructed. But look again more closely: notice those thick walls that can be detected by the thickness shown at window and door openings?

And if you (click to) enlarge the photo you might notice the "lumpy" building sides. Look again at our straw construction house wall photograph just below.

How are Straw Bale Homes Constructed

Straw bale constructed home wall details © Daniel Friedman at InspectApedia.com

STRAW BALE CONSTRUCTION uses bales of straw tied with string or wire as the modular building blocks. Straw bales are stacked vertically in a running bond pattern - each straw bale is placed so that its center is over the end-butt joint of two bales in the course below.

The strawbales are laid 

either on their base (a wall thickness of about 18-22") or on their sides (a wall thickness of 14-18"). For narrow wall sections the straw bales may need to be cut and re-bound to the required length. Small and irregular wall gaps that do not fit a straw bale may be filled with hand-packed wire-mesh or wire lath forms cut to fit the necessary shape.

"Straw" is defined 

as the stem portion of a grain plant such as the stalks of barley, oats, rice, rye, or wheat, but without the grain (seeds) or grain "heads" of these plants.

Strawbale walls are normally, reinforced with through-driven or surface-tied wood, bamboo, or steel re-bar

 rods, and then coated on all sides with a stucco of earth, clay, or a cement mixture, applied either directly to the straw bale wall surface or applied to a "chicken wire" mesh or to clay-coated burlap that has been tacked to the surface of the bales or to the reinforcing bamboo on the wall exterior surfaces.

Strawbale wall plastering 

may be performed entirely by hand, or the builder may use a textured-paint sprayer to first prime the straw wall, making subsequent plaster coat application easier and providing a better bond. During plastering of the strawbale wall, a "cob" mixture of straw, sand, clay and water may be packed into any small remaining gaps between the bales. The straw bale wall plaster recipe varies by location and available materials.

The plaster first coat

 may be an 80-20 mix of sand and clay with chopped straw added for additional strength.

The final plaster coat,

 hand troweled, may also be an 80-20 sand/clay mix with an addition of 4% lime water. This coating will contain less chopped straw or none at all in order to give a smooth hard finish on the wall. Finish coating with lime plaster or similar materials may be applied depending on the climate and building use. For building durability proper curing of the plastered or stucco coatings and final lime or pigmented coatings is very important as hairline cracks can invite moisture into the structure, destroying it.

Post and beam-constructed straw bale homes 

use straw bales to fill in the wall spaces between wood, reinforced concrete, or steel posts and beams that form the structural frame for the home. The frame supports the weight of the building roof and upper floors. In post and beam strawbale construction the courses of bales may be pinned together using vertical lengths of bamboo (two to a bale) placed on the inside and outside of the straw bale wall, then tied together using a stiff wire "needle" to force twine through the bales where necessary.

Load-bearing-wall-constructed straw bale homes 

foundation (if a foundation is provided). Some straw bale homes are built without a masonry foundation, resting the first course of straw bales on compacted earth or gravel.

Our photograph (left) shows the sides of a straw bale built home. The "lumps" visible on the building wall are about the size of a bale of hay or straw - we call this modulo-straw-bale lump size, an obvious indicator of the materials of which this home was constructed.

Some advantages of straw bale construction include

Some disadvantages of strawbale constructed homes include


Straw bale house interior © Daniel Friedman at InspectApedia.com

This straw home photo (left) shows the interior of part of this two story home. Here, too, when the angle of illumination is just right, it's easy to see the straw bale texture of the home's walls. Of course other straw-bale constructed homes may be parged to a smooth wall surface, hiding this straw bale shape.

How durable are straw-bale built buildings?

We have read assertions that well-constructed straw bale houses in Nebraska have lasted for more than 100 years. But as with any construction method, the life expectancy of a strawbale home will depend on both the quality of its original construction and the quality of maintenance over the life of the building.

The type of straw used to produce bales used in strawbale construction may make a difference in the durability of the building. Straw may be comprised of the stalks of barley, oats, rice, rye, or wheat. But the higher silica levels in rice straw make it easier to dry and more resistant to decomposition from moisture.

In the home shown in these photographs, the strawbale constructed home uses load bearing straw bale walls. The load bearing design may be a significant factor in the appearance of the wall cracks and leaks shown in our straw bale wall damage photographs (below).

Our OPINION is that non-load bearing straw bale construction (in which straw bales are used as infill between the posts of a wood, concrete, or steel post and beam structure) may be less likely to experience these problems.

The walls of a load bearing straw bale home must carry not only the weight of the wall material itself but also that of the roof and of the live and dead loads of upper floors in the building. Any condition that increases the chance of cracks in the stucco coating of the straw bale wall increase water, insect, and rodent penetration risks and thus the chances of further rot, settlement, or infestation in the structure.

Where do problems on straw bale constructed buildings most often appear?

The window in our photo (below) shows the wall thickness - a clue that this is a straw bale home. The outside of the window jamb was painted green, the inside white.

Straw bale  home window detail © Daniel Friedman at InspectApedia.com

A good outdoor construction detail on a straw bale home of this design is the inclusion of a slope on the window sill so that it drains without risking sending water into cracks in the straw bale stucco coating. Our second photo ( right) shows one of the places to look for cracks, leaks, and water entry at a straw bale constructed home - at the window and door openings.

Straw bale house window details © Daniel Friedman at InspectApedia.com

...

Straw bale constructed home wall cracks © Daniel Friedman at InspectApedia.com

Our photo above shows a thin vertical crack in the stucco covering of this straw bale home, at the center of this picture.

Straw bale wall crack details and repair history © Daniel Friedman at InspectApedia.com

Our second photograph of a straw bale home (below) shows both cracks and evidence of previous repairs in that same location (click these photographs to enlarge and make the crack details more visible)

Just below are more closeup photos of cracks in the stucco coating of this straw bale constructed house wall.

Straw bale constructed home wall cracks © Daniel Friedman at InspectApedia.com

What special steps should be taken to preserve a straw bale home?

Straw bale wall crack details and repair history © Daniel Friedman at InspectApedia.com

Reader question: How easy or hard is it to repair small cracks in a straw bale home? How easy or difficult is it to cut in a new window or door in a straw bale home wall?

It has been very useful to have stumbled upon your website as I had no knowledge of straw bale construction and its special care requirements.

Since you offered some support, I would like to ask you two things. As you know the house is old. It was built specifically for rental and the quality of most materials, such as window and door framing, and furnishings is below what I prefer in a home. It has potential, though.

Last summer I noticed that a small section (maybe 10 cm.) of an exterior apartment wall had cracked and was open to the elements. I did ask my property mamager to repair it, but I don't know if she is aware of the construction material. So question one is how easy or difficult is it to repair a small section like that?

The second question is how easy or difficult is it to cut a new door or window into an existing wall, as I someday want to put a room addition on the lower, one-story apartment. - N.G., Myanmar

Reply: Advice About Straw Bale Home Crack Repairs and Adding Windows or Doors to Existing Walls

Think of the straw bale wall structure as a thin masonry shell plastered over bales of hay or straw. If water gets into the interior of the shell it invites decay or pests that over time can damage the bales, leading to hollow areas that are structurally weak compared with the as-built design.

So my opinion is that it would be smart to inspect the house from time to time and to try to keep any cracks you see sealed.

How we Patch Cracks in Straw Bale Wall Stucco Coating

Straw bale constructed home wall cracks © Daniel Friedman at InspectApedia.com

Typical repairs to straw bale house cracks are simple re-plastering, or chipping open a crack wide enough that the plaster repair will be mechanically sound, then re-plaster and re-paint the wall.

By "re-plastering" I refer to using a cement mix, not actual "plaster". The crack may need to be opened a bit wider and cut to an inverted "vee" shape to get the best mechanical adhesion of the patch. Very fine cracks in the straw bale stucco coating, say less than 1/16" in width, might seal up ok if kept painted.

If you find actual damage that is resulting in movement of the structure - say crushing under a floor joist or beam - then it would be appropriate to open the wall to see what's going on.

It would be simple to add a post and pier if necessary, you don't have to chop open the whole wall and try replacing bales. But if you are not seeing structural movement, that more extravagant repair should not be necessary - just keep cracks sealed as best you can.

How we Cut Openings for Windows or Doors in an Older Straw Bale Home

Straw bale wall cut for window © Daniel Friedman at InspectApedia.com

I'm more nervous about cutting openings for windows or doors, especially when both of us are just thinking by email and are not on-site to see exactly what's going on and exactly what is inside of a wall that we cut open. In general, a too-glib answer is that you can do just about anything to any building - that is it's possible.

The devil is in the details: just how much trouble and expense are we going to face, and are we sure we're handling the change with enough thought that we're not messing up the rest of the structure.

If you cut a door where there is already a window, often that's pretty easy as there is already a header over the window opening to carry the weight of the wall above. So if the top of the window is high enough to fit a doorway, just cut the bottom wall out below the window. It's not going to change the structure.

But if we need to make a new opening where there was none, most likely you'll want to frame in a header beam to be sure there is no sagging or cracking in the wall above. The header is carried on posts to concrete piers poured into the soil deep enough that there won't be any sinking and thus there won't be any cracking in the wall. Then the door or window jamb is framed into that opening.

Find Out More About Your Straw Bale Home Construction

Finally, if by chance a neighbor can tell you who built the straw bale home, we might find out if the original builder is still around, as s/he will also be familiar with hidden structural details in the home and somewhat familiar with straw bale construction.

A clue would be whether or not we can find any other such homes in the neighborhood.

Straw Bale Construction Guides & Codes

Photo of straw bale house in Poland, subject of Pierzchalski's study - cited & discussed at InspectApedia.com


 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-07-05 by InspectApedia Publisher - understand the general nature of the defects to help understand the building's future life

@PKZ,

Thanks - I hadn't seen those other photos.

In addition to making a through inspection and inventory of every damaged spot in the building's walls or roof, and cataloging the cause (usually leaks), you'll want to understand the general nature of these defects - their underlying cause such as improper construction, wrong components, missing flashing, etc. as that will tell you what's in store over the building's life.

On 2023-07-05 by PKZ

@InspectApedia Publisher, electrical components are in place. And there is an operational toilet and kitchen sink. But other that those, yes, pretty much a shell. The majority of the bales are visible, with only one section where someone tried to do the interior with cement mix. The large cracks on the outside are worrisome?

On 2023-07-05 by InspectApedia Publisher - you want a thorough inspection for the location and cause of leaks and fix those first

@PKZ,

I would want a thorough inspection for the location and cause of leaks - we need to fix those before fixing the building.

Great news that you can see the interior of this straw bale house - that will make assessing the amount of water damage easier, and if we need to replace a bale or part of one, we know exactly where we are - much easier than if the home had been finished inside.

I don't see any wires or plumbing - which at least means it hasn't been run where you don't want it. This is just a shell.

On 2023-07-05 by PKZ

@InspectApedia Publisher, no hollow sounding area. But there was a window opening that was not enclosed for sometime which definitely allowed water into the house.

Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ

...

Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ ... Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ

On 2023-07-05 by PKZ

@InspectApedia Publisher, thanks for the quick response. Work stopped about 2 years ago. The builder passed away.

Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ ... Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ

On 2023-07-05 by InspectApedia Publisher - Am I walking into trouble by buying an unfinished strawbale house in Arizona?

@PKZ,

Maybe. My inspection, from here is a bit thin on facts.

Even in a dry climate like AZ, a combination of age, leaks, and sometimes rodents or other critters can digest and cause settlement of the original straw (probably hay) bales used to construct a house. The result can be a hollow area behind that stucco coating, usually near what was the top of the original bale, and of course settlement, especially where framing, such as for a window, rested on a bale that is now smaller or deteriorated.

How old is the home?

When did work on it stop?

If you simply tap on the stucco coating, are there obviously hollow-sounding areas?

Have you identified the probable cause of damage such as

- over-watering when plastering the bales

- leaks (yes it does rain sometimes in Portal AZ - according to weather dot com, Portal has 7-8 inches of rain a year and about 73 days when rainfall occurs).

If enough time has elapsed since first leak that you suspect rot, rotted straw bales will need to be replaced and any damaged framing repaired, not just to stabilize the building but to avoid an incipient mold issue down the road.

Small areas of damage can often be repaired without removing whole bales, cutting repair openings, removing bad bale material, pushing in clean dry straw, and re-plastering: one would have to cut open the wall in the area of damage to determine its extent and thus the extent of repair.

Watch out: lots of water damage repair writers send you hustling out to buy a moisture meter to map the "damage" - Really? I've found extensive damage at various sorts of buildings that measured perfectly dry, either because the damage was old (the water was long gone) or because the moisture meter couldn't read through the wall, ceiling, or floor, to find the damage.

So if your expert is over relying on a moisture meter things could be uglier than she or he tells you. Be sure to read MOISTURE METER ERRORS

Please post some photos showing me the whole building, esp. from the damaged side and then some closer looks at the window and cracks - one photo per comment but as many comment-photos as you wish.

On 2023-07-05 by PKZ

Considering buying an unfinished strawbale house. 145 W Ortiz Lane n a Portal AZ 85632. There are many cracks on one side of the exterior walls and a window that does not sit right in its frame. Am I walking into trouble here?

Here's a picture of how it looked before they covered up the open frame and exposed bales.

Portal, AZ straw bale house with some defects showing (C) InspectApedia.com PKZ

On 2017-10-17 by danjoefriedman (mod) - can we seal them cracks in the stucco on our straw bale house with a "cement mix"?

Yes, Cynthia; typically the stucco-like plaster used on straw bale construction can be mixed as a patching compound, or for small repairs you can buy pre-mixed canned concrete patching material.

Don't just smear patch over the surface where a crack appears, as it may not adhere well. Chip out the crack wide enough that the new patch will have a sound mechanical bond.

If the stucco is thick enough we want the crack gouged open in the shape of an inverted vee - wide portion facing inside towards the wall interior - for a strong mechanical bond of the patch. Scrape off loose paint, prep the crack, then apply the repair, let it cure a week or more before painting.

Yes for hairline cracks you can try foundation sealant paints as an at-least-temporary repair. But remember these paints don't have much elasticity so if there is thermal movement across the crack it will crack through the paint.

For this case I use a mesh reinforcing tape (try drywall fiberglass mesh tape or equivalent) over the crack before painting on the sealant - that gives a much longer life repair.

On 2017-10-17 by Cynthia Lunge

Just purchased a Straw Bale house...with cracks in the exterior. Some thin and some maybe close to a quarter inch. Thankfully this wider ones are under the eaves. We want to seal ASAP and believe the exterior to be made of stucco.

So, can we seal them with a "cement mix"? and then repaint the whole house with a textured tinted cement mix?

We heard so much about a silica base paint to allow the house to breathe and not withhold moisture. Does this apply if the home appears to sealed in stucco? It looks like paint with a sandy layer added within. The house is probably 20 years old and seems in great health.

Need help to protect this house form winter. Please Thanks Cindy and Frank

On 2017-01-21 by danjoefriedman (mod) - will straw bales be an adequate insulation method?

Thanks, Joe.
Straw Bale is an interesting construction idea.

The straw bale house illustrated in these photos was first inspected (by me) back in 2005. It's still in place, has been sold and occupied for some time now. From driving by - I've not been inside - it is apparent that there have been some repairs to the exterior stucco coating on the bales.

The home illustrated is in San Miguel de Allende in Guanajuato, Mexico - an area that is often quite dry but still subject to heavy rainstorms, and as the home is at the edge of the city there's no shortage of little critters who might enjoy living in its walls. I agree that that's a concern, but I didn't see that problem when I inspected the home.

I speculate that in an older straw bale home one may indeed find an occasional infestation problem. But, then, mice will also move into fiberglass insulated wood-frame wall cavities, ceilings, floors, too.

Rigid foam is not a reliable barrier as it's chewed through by rodents and insects when they want to get by.

On 2017-01-21 by Joe M

This is a very interesting article. Considering the high cost of rigid foam and fiberglass insulation, I have to wonder if it would make sense for me to stack up a bunch of straw bales to fill in the space between the exterior wood siding and interior wall cavity. This is for a post beam construction.

My only concern would be the idea of keeping the cavity sealed up well from critters and moisture. Possibly just use 1" rigid foam first to act as a barrier from the outside. Then stack the bales up along that on the interior side. Then put up drywall or whatever. That's a thought for sure.

 


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