Archive for Straw Bale Building

A review of the Natural Building Companion

Two years ago I saw a presentation by Ace McArleton, co-author of the Natural Building Companion, and based on that I knew I needed to order the book. For a while it sat on my shelf, alongside a collection of other books about building and natural building. However it has distinguished itself from its companions in the true test – when I have a question, or encounter a problem in my work as a straw bale builder, it is the first book I reach for. I now consider this book to be an essential reference for those planning to build with straw bales, clay-straw or other natural building materials – and while it is useful for the pros, it is still accessible for beginners.

Jacob Deva Racusin and Ace McArleton have spent the last decade working on high performance natural building – marrying the building science of the superinsulation and passive house movements with natural materials. The natural building movement in general has been moving to adopt better practices around managing heat loss, particularly making buildings more air tight, but the Natural Building Companion is the first book to address it comprehensively, and also to offer practical solutions to common problems.

For example, it’s common to couple straw bale construction with timber frame, however the junction of each post or beam with the plaster is likely to become an air leakage problem – movement of the building can even break caulking along these joints when it is used. The best solution to this problem is air fins that run behind the post and several inches under the plaster. Racusin and McArleton discuss proper installation, and share their experiences using different materials as air fins – and the choice of material is critical since the wrong choice can simply displace the crack from the post to the edge of the air fin, or cause other problems.
Bales squared before installation
A controversial topic in the bale building world is the use of cement-lime plasters. A track record in Ontario has shown that cement-lime plastered buildings can work in our climate, if designed properly. However I would agree with Racusin and McArleton that cement-lime plaster is not the best choice in this relatively wet, cool climate – and the authors offer a very good alternative plastering system that is more appropriate for our climate. A lime-stabilized earth base coat with a lime finish coat is a system we learned about from European builders, but we had just plastered our first house with this system when we discovered that there was a wealth of knowledge just across the border in Vermont. The authors have mastered this system and share the details of it in their book.

The treatment of moisture management is also thorough; like everything in this book it starts with design considerations and follows through to building techniques and detailing. The authors have also done extensive testing of their buildings post-construction to see how well they performed over time, while they were being lived in.

Vampire stakes

Vampire stakes

I even learned tricks to improve our bale work, such as squaring bales before installing them, or the use of “vampire stakes” to anchor straw bales to post and beam structures – the most functional and elegant system I have yet seen for doing this.

The book comes with an instructional DVD filmed at Yestermorrow, which shows exactly what they explain in the text, filmed at each step along the way. I’ve only consulted this a few times so far, but each time it clarified something that wasn’t quite translating from the page for me. Beginners to straw bale will likely want to watch it right through.

I have only picked out a handful of examples, but the Natural Building Companion covers every step from design, through construction, to finishing details, and does it all well. They take it from philosophical underpinnings to technical details of the systems they have evolved with their company New Frameworks.

In short, the authors nailed it, they have written a standard for the natural building world. Having used the book, and spent some time with the authors, I would also agree with Andrew C. Gottlieb that these are definitely builders I’d want to work side by side with, for their professionalism, expertise, and knack for having fun.

I would recommend their website and blog as a reference, in particular I’m keeping an eye on the development of their new system that aims to reach passive house standard while using straw bales. Here is a video of Racusin and McArleton discussing high-performance natural building.

Will straw bale buildings last?

After seeing problems in a few straw bale buildings, I’ve been thinking about this lately: is it a truly durable building system? By which I mean, will  a straw bale house measure its lifespan in centuries rather than decades? I’ve concluded that most will, some won’t. The ones that won’t are predictable, however, and for the most part they break the rules.

This wall is ready to be replastered after wet straw was removed. It had no overhang at all.

Architects occasionally design straw bale homes with no roof overhang, for instance. I’ve seen this twice, and in both cases an overhang was added before construction was completed. In one of them there were already some moisture issues a year or so after the wall was closed in. Water was sheeting down the wall in spring rain storms and working in through cracks. These were a few horizontal cracks which had reopened after crack filling. Straw at the base of the wall was saturated and had to be replaced – which was not as hard as I thought, and in a weird way I found that encouraging for the question of longevity. With the overhang in place I think this will be one that does last.

Other houses that I worry about don’t break the rules so blatantly, rather they push them a little, but they are on exposed sites. Driving rain is the enemy of straw bale houses, and gable ends are particularly susceptible. If you’re thinking of building a straw bale house on an exposed site – a hill or a lakeshore, or any site where you might consider using a wind turbine – your design must be impeccable. You might want to consider a bungalow with good overhangs all the way around, you should certainly avoid a large gable end on a windward side of the house. Gable ends in general should have some kind of skirt roof, and you may want to consider siding the upper part if it’s large or particularly exposed.

Cement-lime plaster tends to make things worse. There’s an unfortunate tendency to gravitate towards cement-lime on very exposed sites because it is the most durable plaster. Cement-lime won’t erode away under driving rain, but it will trap in moisture more effectively than any other plaster. High lime content helps a lot, but pure lime is better, or an earth-lime hybrid system; in rare cases exterior earth plasters may even work on their own (note that the right paint is important for earth and lime plasters). In any case, if you’re very worried about your plaster eroding under driving rain, you probably have a design problem and cement-lime plaster is likely to make it worse. You need to redesign, or possibly you just shouldn’t be building a straw bale house there. An oft-overlooked alternative that can eliminate most external moisture issues, even on exposed sites, is to use siding or rainscreen over bale walls. And keep in mind that whatever you build on an exposed site, bale or otherwise, you’ll need good design and attention to detail.

Cracks must be filled. I’ve seen a house that went maybe 8 years without crack filling and painting, and it was fine! But I’ve also seen disastrous results from unfilled cracks. Again, the site seems to make all the difference, but there’s no sense pushing your luck. Fill your cracks within a few months, or if you plaster in the fall, wait until the following spring or early summer – but not years.

This sounds like a whole lot of bad news, so why build straw bale at all? Is it worth the hassle, and is it really a sustainable wall system? To put this in perspective, when a 100-year-old hay-bale house was dismantled in Nebraska the hay was in such good shape that cows ate it. Or consider that straw bale building is not alone in having had its share of mistakes – modern building practices have created a “perfect storm” of stucco failures on conventionally built homes. In some ways, bale walls are better, they can be more resilient than some conventional wall systems. As soon as you add  insulation to a wall you’re inviting moisture problems – the more insulation you use, the harder it is for the wall to dry out if any moisture gets in, because the middle of the wall tends to stay cool. Superinsulated homes are built to have very low air leakage for energy efficiency, but also because air leakage can cause moisture problems if water condenses in the wall.

Straw bale walls can likely handle small to moderate moisture loads better than conventional wall systems because of the vapour permeable plaster skins on either side, and because the straw itself can act as a large reservoir for moisture without ill effects, so long as it does not exceed an upper limit, and the conditions occur for drying. It’s still very important to air seal a straw bale home properly, and many natural builders have been slow to realize how important air sealing is. In my experience those days are over and air sealing is a priority for most natural builders, which means some kind of air fin behind all plaster joints, and of course good detailing around electrical boxes etc.. This is not just a question of energy efficiency, but also is likely to extend the life of the home.

There are other benefits to straw bale, of course, that I should mention briefly: A relatively high R value (at least double that of a 2×6 stud wall with batt insulation, but still less than most superinsulated homes); low embodied energy and local sourcing of the building materials; and aesthetics. Straw bale is not for everyone, and is certainly not the only ecological way to build, but it has a role to play when done correctly.

A literature is beginning to develop around moisture control in straw bale walls. Here’s a short list of important resources

Design of Straw Bale Buildings

Moisture Movement and Mould Management in Straw Bale Walls for a Cold Climate

Moisture Properties of Plaster and Stucco for Straw bale Buildings

Building Science for Strawbale Buildings

Many of the best practices of design, air detailing, flashing, and other details of conventional homes also apply to straw bale homes, and for this one of the best resources is the Builder’s Guide to Cold Climates.

The Original Nebraska Straw Bale Buildings

For a long time I wanted to see the original 100-year-old straw bale buildings in Nebraska, so on a drive across the continent I included Nebraska on the tour. My first stop was Arthur Nebraska, where I met up with Jake and Lucille Cross.

Jake Cross took me to see the Martin/Monhart house, a home that was built in 1925 out of baled late-season hay. It was formerly owned by his wife Lucille’s parents. What struck me most about this house is how normal it looks. Modern straw bale homes emphasize the straw, with rounded corners, unique plasters, and often slightly wavy or uneven walls. My first thought was that the inside of the Martin/Monhart house had drywall over top of the bale walls, they were straight and flat and covered with wallpaper. This could have been my grandparents’ house. Jake had me stand right beside the wall and look down its length; from this vantage point a slight wave could be seen where the wall meets the ceiling- what I mistook for drywall was the bale wall itself. Only in the windows could the depth of the walls be seen, showing the tremendous insulation value of nearly two feet of baled hay. Lucille told me the story of the day a tornado roared through the town, tearing up trees, blowing out windows and sounding like a freight train running through the middle of town. As soon as the tornado had passed Lucille went to check on her parents only a block away from the path of destruction. “We found them playing cards,” she recounted, “they had no idea a tornado had passed, they didn´t believe us at first.” Bales are a great insulator against sound as well as temperature. Standing there surrounded by the old furniture, I could imagine the couple peacefully playing cards, blissfully unaware of the destruction that came so close.

The Martin/Monhart house was one of the later homes to be built in the original wave of Nebraska bale building. One of the first was an 1886 school house, which suffered an ignominious fate. Unfenced and unstuccoed, by 1902 it was reported that

The sandhills of Nebraska

the building had been eaten by cows. The invention of straw and hay bale homes in the sandhills of Nebraska was almost inevitable because of a combination of factors. The first was the invention of the horse powered hay press (hay baler) around the 1870’s-1880’s, which for the first time created the raw material for bale homes. Secondly, the traditional Nebraska sod house didn´t work all that well in the sandhills. The turf on the uplands tended to fall apart easily and the soil in the lowlands was too valuable for growing crops to use it as a building material, if any alternative could be found. Nebraska resourcefulness and technological progress met in the sandhills and the bale house was born.

The Haslow House

After leaving Arthur, I Visited the Haslow house, which took me through the heart of the sandhills.

I pull over to the side of the road. It’s perfectly still, but stormclouds form great anvils on the horizon. In the sandhills, especially around sunset, the land and the sky somehow seem equally real and equally fanciful, as though reality lives somewhere in between. The sandhills have a surprisingly dramatic, otherworldly beauty to them.

Rich Haslow is a rancher who runs the operations of the Nebraska Boys Ranch. In some ways he´s pretty traditional, for instance he´s one of the few farmers around who still stores his hay in stacks instead of bales.

Interior of the Haslow House

Someone had a baling machine here at least once though, in 1913. That was the year Jason Snow built a house here out of rushes baled from a shallow lake that still lies behind the house, and which to this day remains filled with a thick cover of tall rushes (it is named Rush Lake). This baling up of whatever was at hand to use as a building material was typical. Many of the original bale homes were made from wild prairie grasses dominated by little bluestem, harvested from the hills late in the season and carted down to the stationary horse-powered hay press to be made into bales. Other houses were built from various straws such as rye straw, or from rushes as the Haslow house was. The term stationary hay press is a bit deceiving, as they tended to move from farm to farm, hired out for a few days at a time to bale hay for sale, storage, or building.

The Haslow house was built in the traditional “Nebraska style,” or load bearing form. This simply means that the weight of the roof sits directly on the straw wall with no wood framing. Post and beam homes with straw in-fill are more common than load bearing ones in modern straw bale construction (though both are common), but the original bale buildings were made to use as little wood as possible. Just as in sod houses, no wood was needed to support the roof in bale buildings.

A doorway through the straw bale wall shows its width

Nebraska style buildings have stood the test of time – the Haslow house still wears its original coat of 1913 stucco, which is in good shape other than a little cracking and settling. The hay used in these houses has little or no rot after nearly 100 years. Standing in his 100-year-old bale home, Rich Haslow related a story to that effect. “They tore down one of these old bale houses near Lakeside, they spread the hay out on the ground and the cows ate it!” The only problem in his own house was that the hay can trigger Rich´s allergies, which is a problem that is not usually seen in newer bale buildings. Modern bale buildings are nearly always built with straw, which is less likely to have issues with rot, or allergies – perhaps that´s the difference, or maybe there are just more gaps in the wall 100 years later. Despite the allergies Rich said “we have no complaints. It´s a good little house.”




The traditional Nebraska Soddy

Before I left he took me to see a nearby sod house. Rich and Rhonda Halsow started their marriage in this house, while his parents were living in the bale house. “We think we might be the only couple of our generation that started off our marriage in a sod house,” Rhonda said. Fitting, perhaps that they followed it up with a bale home. A thunderstorm was crossing the horizon as I drove off.