Archive for the ‘Load Bearing Construction’ Category

A Conversation About Load Bearing Straw Bale Construction Wall Heights

Here’s an interesting question I received today.  I hope to hear more about this idea of multi-story load bearing structures in the future.  Perhaps you have some input to share…

Andrew,

Although you said that you could not have a 2 storey LB building  because of the wall thickness/height ratio – could it not be done with a box beam between the floors with a second beam beneath the roof. Surely this would then start the ratio again? From other straw bale builders I gather that the bales would support the weight and therefore with an interim box beam this has to give it sufficient strength?

Here’s what I said in response (with a little expansion):

I would see how this could work. It seems to make sense; however, the biggest issue I hear from engineers is that the overall weight of the walls is still transferred to the foundation in a direct load path and thus the wall height ratio cannot be started over. The middle box beam could ultimately become a hinge point for the wall if under large “out of plane” loads. In general it’s dangerous to have a lot of weight up high in a wall system or building because the tendency is for that wall to rack and/or tip over if under loads such as wind or earthquakes. That’s why in post and beam structures, and all conventional construction structures for that matter, there is a specific lateral bracing requirement that must be met as well as an “out of plane” resistance requirement. With so much weight in the walls there could be a risk of such a collapse.

I’ve heard of three story load bearing structures in Canada that were engineered and built relatively recently; however, I don’t think they have been up long enough and seen enough of nature’s forces to give us adequate information as to the long term viability of such a building. I’m eager to watch the time pass on those buildings and see how they fare. I think it really could be a major improvement to the load bearing construction world if these structures prove reliable and safe over the long haul.  I’m hopeful they will.

Interesting Approach to Adding Openings in Load Bearing Construction

I just got an email from someone who plans to install his windows and doors the following way. I think it is an interesting idea as it will provide for very good compression of the bales and a very quick construction of the walls. This is in line with how additions can be added to existing straw bale homes. I always suggest that if people have specific intentions to expand later on down the line that they plan for the expansion by leaving electrical out of the area where they plan to cut in the new hallway.

Check out the idea sent in via email and let me know what you think about it.

1. The spaces required for windows and (over sized) doors are not left open but
rather the walls are built as full walls with no spaces. The lintels for the
doors and windows are however, put into place.

2. Once the walls are at roof height, wall plates are in place and the bales
have been compressed and have settled (some 2 days or longer after
compression), the door and window spaces are removed via chainsaw or other
appropriate method, from below the lintel.

3. The sides and bottom rails of the door/window spaces are immediately put
into place and the sides are attached to the bale wall by pinning through the
timber into the bales with wooden dowels. Care will be take to ensure that any
part-bale section within the space that are small enough to fall out, are kept
in place. This should not be a problem however, since once the bale compression
has taken place, the compressive force should keep the straw in place even after
being cut.

4. The pre-made window can then be attached to the frame or constructed within
the frame from scratch. Doors are made to fit the space.

Building Buttress Walls to Support Out of Plane Wall Loads in Load Bearing Construction

When building a load bearing straw bale wall, you need to support the wall from falling over into the house or out of the house. The direction in concern is called the out of plane direction and is perpendicular to the wall. A wall should be supported in a ratio of 13:1 (length to thickness of wall). For a standard 3 string bale, this is every 25′. The question often arises about how to support a wall where an intersecting wall is not desired, such as in a living room or kitchen.

buttress-wall.jpgOne way to accomplish this is to use buttress walls. A buttress wall is a wall that does not go full height of the main wall. Instead, it steps up from the bottom to the top with the base being its widest point and the top being the same width as the main wall. The bales in this buttress wall should be interlaced with the bales of the main wall for maximum benefit.

The best part of a buttress wall is that you can support your main wall while still keeping an open feel in the house. The buttress can be used to hold plants or display other items that make sense in the room. The walls can also be filled in so they do not step, but are a diagonal slope if that look is preferred. There are many things one can do with a buttress wall to both support your main walls and improve the design of your house.

Anything over a ratio of 13:1, that’s 25′ for a standard 3 string bale as pointed out above, should be supported by an intersecting wall. A buttress can be designed so that the bottom course is roughly a bale long, the second course is 3/4 bale long, the third a 1/2 bale and so on. The width of that wall (length on the buttress but it looks like width in comparison to the main wall) is determined by the height of the main wall. Figure how many courses you have with the top course ending up flush with the main wall and then work out by 1/4 bale length at a course from there. That will determine how long the bottom section needs to be.

Buttress walls have been used for years in masonry and other forms of construction. They are a time tested tool that can be used to improve the strength and design of your straw bale house. Have fun with them. Make them a part of your dream, not a bummer of a wall you don’t want but need to keep your building safe.

Window and Door Bucks

When making window and door bucks for your load bearing home or other structure, you have a few choices to make. What size wood do you want to use? What design should you employ? How will you attach the bucks to the wall?

I find that knowing the answers to these questions BEFORE I start building is more than important, it is imperative. If I do not know the details of the structure before I start, I am sure to run into hang ups along the way well beyond the normal hurdles that we all encounter when building. For me, the design of the buck comes first. By creating a design, I can answer the other two questions with ease. In some cases, I will design a buck with angle side walls to ease the flaring of the window wells. in other situations, I will use flat, simple bucks to anchor the windows and doors. In fact, I know by the utility of the window well what design I will use. If the window will double as a seat, I am more likely to use a flat design to allow people to sit comfortably in the well. If not, I will use a flared well to bring more light into the room.

In either case, a flat or angled buck, I double the design for the doors so that a uniform look runs through the house. In addition, I use plywood for most of my bucks, whether angled or flat, to give extra nailing for the mesh. The plywood extensions on the structural framing cut down on dimensional lumber and increase the ability to anchor the mesh to the bucks as noted above.

The advantage of using larger structural members in in the anchoring of the buck to the wall. With a deeper unit, say a 2×10 as opposed to a 2×4 with plywood, the dowel that is later driven into the bales goes through more “meaty” wood. The deeper the wood member, the further towards the center of the bale you can get while still doweling through structural wood (not plywood). A 12″ dowel with a 1/2″ to 3/4″ diameter is sufficient to anchor the bucks to the bales. A layer of plaster’s lath around the edges further strengthens the attachment.

No matter what design and anchoring you choose, be sure to know what it will be before you start building. As in any aspect of construction: the more you know before you start, the better! Happy Baling!

Even More Load Bearing Straw Bale Answers

OK, I have had a ton of load bearing questions coming in both in comments on this blog and in my email. So without further ado, I am going to answer the ones that keep popping up:

Question: Why should I use load bearing construction instead of post and beam in-fill?

Answer: It is a decision you will have to make on your own. Both options provide advantages and disadvantages when compared with each other. Load bearing is great for the owner builder and it is a bit less resource heavy. In truth, it comes down to personal preference. I have described the pros and cons of these types of construction in the past, so I won’t do it again here, but the fact remains that they are both amazing forms of construction that need to be considered strongly. Whichever you choose, you will have a beautiful and efficient home.

Question: Is there a money-back guarantee on the DVD?

Answer:
Absolutely. And it’s for a full year, no questions asked.

Question: Why aren’t rubble trench, rammed tires, or earth bag foundations appropriate for LB?

Answer:
Those foundations can be appropriate for LB although it will take a lot more work for you to convince the building department of that. These foundation systems are considered alternative by almost every jurisdiction. That is not to say you should avoid them; however, you will need to KNOW YOUR STUFF when you present them to the building department. How will you anchor the bales to the foundation and the foundation to the Earth? How will loads be handled by such foundations? Can you back up your thoughts with data? I do not have the data for these questions as I tend to build traditional foundations on my homes. Don’t give up though. If you want to make it happen, you can.

Question: Where is the link? Where will it be released?

Answer: We will be sending you the link on Wednesday, April 11th just before noon eastern time.

Question: Are there any alternative methods for those who don’t wish to use the wire? Won’t the wire stretch/sag and pull away from the walls resulting in cracked plaster?

Answer: The wire will not sag and stretch as long as the bales have been properly pre-compressed. If the bales cannot compress further, the wire cannot sag. In addition, the plaster glues the mesh to the bales with a very strong mechanical bond. If you do not want to use the wire mesh, you can avoid it as long as you are not counting on it as your structural shear system and you are using a natural plaster. If you use a cement based plaster,
you will be required to use some mesh reinforcement. Another option is to use plaster mesh in place of the wire.

Question: I hear that you have some bonuses. What are these?

Answer: I am offering a couple of free teleseminars for the first people to order. Without giving it all away, some descriptions are below.

1. A 60-minute Q & A teleseminar with me where I answer any questions that you have after watching the DVD. I tried to leave no stone unturned but I am sure there will still be some
questions. I will collect those questions via email and answer them on this live call.

2. A 60-minute teleseminar and Q & A session with me discussing specific details of Green Construction. My DVD covers all aspects of load bearing straw bale construction, but in order to beef up your knowledge of green building I am doing a special report that will give you specific details about how to green up your existing home with easy to accomplish tasks. You will learn how to save money on your annual cost of living AND help clean our planet.

Question: I currently own your other DVDs, how is this one different?

Answer: This DVD focuses on load bearing construction which is very different from post and beam in-fill. In addition, it is set up so that the viewer can follow along over a course of days. The project is laid out so that you can build along with the DVD and know right where you should be (time wise) per the schedule on the DVD.

Question: OK I’m going to come right out and say it. I’m terrified of roaches, rats, mice, snakes, and all sorts of creepy crawlies. So what about these critters and straw bale? Surely the straw becomes a nice place for them to live.

Answer: Actually, the straw is not a great place for any of these things to live for a number of reasons.

1. The straw is so dense that the critters cannot get a round in it.
2. There is no food source in the bales for any of these critters.
3. The plaster is so thick and hard that they cannot get into the straw to begin with.
4. There are much easier places for them to live that provide a lot more for them then the inside of your well detailed walls.

Question: I am a little concerned about the safety of a load bearing building because I live in an area prone to Tornadoes. Can you address that?

Answer: Straw bale walls are thick and durable. As long as they are anchored to the foundation properly, they will do well in high wind areas. Tornadoes tend to have a lot of risk and danger
associated with flying projectiles. Those projectiles can puncture a conventional wall with ease, killing the occupants inside the home. I do not have any data showing that bale walls are any better, but I know that cement and thickness have an impact on the ability of a projectile to get through without being slowed down. My common sense suggests that a bale wall would be safer. I would love to see some one do some research on this and provide some data for us all.

Question: Is this just a repackaged product that you already sell?

Answer: No. This is brand new. You can’t get it anywhere else in any other form.

Question: I will be away on vacation when you launch your DVD, how can I get it?

Answer: If you REALLY can’t be at your computer, send an email to mailto:info@strawbale.com and we will see if we can figure something out for you.

Some Load Bearing Questions Answered

Straw bale construction questions seem to follow me where ever I go. I’m writing this blog entry from a hotel in Oakland California. I’m here with my son’s ice hockey team and I thought I’d take a few minutes to respond to the many questions I’ve gotten about our upcoming Load Bearing Straw Bale DVD. In fact, it’s safe to say that we have NEVER had this much interest in one of our straw bale DVDs BEFORE IT WAS EVEN RELEASED.

In any case, rather than sending you a super-long email, I thought I would answer some of the straw bale questions directly on my strawbale.com blog:

Question: There’s a lot of information out there about load bearing straw bale construction, what makes this DVD unique?

Answer: After teaching thousands of professionals and owner-builders over the years, the thing I keep hearing from people is that they want a step-by-step system that actually teaches them
how to build a load bearing structure. Most of the information available out there shows how wonderful straw bale is, but there is little that actually teaches people how to create with the
materials.

So over the last few months, I created the perfect system to overcome this common complaint.

First of all, I created a complete step by step guide that walks you through the exact details needed to build a load bearing straw bale structure.

Secondly, the delivery of the course is truly unique. It’s set up in a day by day breakdown of the process that allows you to properly allocate the time you will need to build the exact structure used as a teaching piece in the DVD. It is the perfect practice structure for anyone interested in building their own home.

Of course, you may still have questions and that is why my blog, consulting services and customer service are available to you for follow up. I have hundreds of comments from people thanking me not only for great products (in regards to my other DVDs), but also for unmatched follow up and help during the process.

The bottom line is that this DVD isn’t a “wouldn’t it be nice if you could build a home like this” approach like so many other resources. It’s completely step-by-step, both in the content and
the delivery.

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Question: When is the course going to be released?

Answer: The release date is Wednesday, April 11th at noon eastern U.S. time.

We have a couple of nice bonuses for you as well, but the number available is limited both in quantity and time. In other words, you will want to act quickly if you want to receive the bonuses. People on my Advanced Notice list are going to get the first opportunity to get these bonuses. If you are not on my advanced notice list please visit:

http://www.strawbale.com/countdown

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Question: Can I get a load bearing structure approved by my building department?

Answer: Absolutely. It may take a bit more effort to convince your building department that a load bearing structure is acceptable, but it is possible. There are three basic approaches to use.

First, find out if there is a load bearing straw bale code in your area. Some jurisdictions already allow for this type of construction under a specific code. Some allow for it under what is considered the alternative housing section of the code. Do the research primarily without contacting the building department. Once you have some information under you belt, make
the call to the building department to clarify any remaining questions you have.

Another option, should you discover there is no specific code that speaks to your desire to build a load bearing structure, is to take a copy of an existing code from another jurisdiction to the department and show them that it is an acceptable building method. In fact, it is so acceptable, that states other than your own, for example: Oregon, recognize it with an official code addendum.

Finally, if you find neither of these approaches gets you where you want to be either because of the building department’s discomfort or the limitations of the code itself, then hire an engineer to create stamped drawings for you. With these drawings in hand, the “risk” as the building department sees it is no longer in their hands but on the shoulders of the engineer. This is a great option because although it costs a bit of money, it allows you to work directly with a licensed individual who can draw the building just how you want it and confidently stand behind it.

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Question: Can I build a multiple story load bearing straw bale home?

Answer: The simple answer is no. The height of a load bearing wall is limited by a ratio to its width and therefore, can only stand around 10′ if using a 3-string bale.

It is possible to build a load bearing home with a loft. In this situation it is necessary to build a steep roof assembly and start the floor at 8′ even though the walls are 10′ tall. It takes some planning to make this happen and some special considerations are needed for the construction, but it can be done. This basically leaves you with a story and a half.

As the field advances and more engineers get involved, I think we will see ways to build multiple stories with load bearing walls; however, we are not quite there yet. For now multiple story bale
homes need to be either fully non load bearing or a hybrid system which incorporates structural members in specific areas to handle the loads of the second floor.

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Question: How do I attach a roof to a wall made of straw?

Answer: Underneath the roof system, directly on top of the bale wall, lays a box beam. This beam is made of wood and is attached to the foundation by means of strapping. The roof assembly is then attached to this beam as if it were the top plate of a conventional home.

Some very specific details need to be addressed in the creation of the box beam which are better shown than described. I go over exactly how to create a box beam for strength, ease of
installation, and effectiveness in the DVD.

With the box beam in place, building a roof is no different than it would be on a conventional home. This is the one place that carpentry skills are truly needed when building a load bearing
house. The other areas in which wood is used (toe ups and window and door bucks) require minimal skills; however, building a roof is as simple or as difficult as the design of the roof. In the
DVD I show you how to build a simplified shed roof, the easiest of all roofs to build. If you plan on using a different style roof, I strongly suggest you study roof carpentry from other productions and then practice it on a small structure before you start your home.

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Question: How much will the DVD cost?

Answer: We will be releasing the price soon. I can say this, many straw bale workshops these days are going for $700 – $800 for a 5 day course. Some workshops are going for as high as $1,000.00. This DVD will be priced MUCH lower.

And you won’t have to leave home, take time of work, or build a structure on someone else’s land! You’ll be able to study and watch this DVD over and over, at your leisure, in the comfort of
your own home and build your own straw bale structure on YOUR land.

Studies have shown that for optimal learning, most people need to hear and see material more than once. You just don’t get that in a live workshop setting. The way I have structured this DVD walks you step-by-step through the load bearing process. It’s like having me for your very own private workshop. With this DVD you can truly master the material so that you have the same step-by-step techniques I use over and over again when I build my houses.

I will have more updates and answer more questions in the next couple of days, so keep an eye on this blog.

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Your comments are very welcome. Please feel free to post a comment to this blog entry about the report or any aspect of load bearing.

Happy Baling,
Andrew Morrison

The Advantages of Load Bearing Straw Bale Construction

The strawbale.com team just came back from a much needed break. We took our kids skiing over the Spring Break vacation and had a blast. Dicken Weatherby, the web guy for strawbale.com, and I had a chance to chat about the advantages of Load Bearing Straw Bale Construction. Dicken brought a small digital recorder with him so we were able to record the conversation.

To listen to this interview/podcast on your computer please click the following link or right click to download the podcast to your hard drive: Building Green Podcast: Advantages of Load Bearing Interview

Would you like to be alerted whenever a new audio or video podcast is added to this blog? If so click here to subscribe to our Building Green Podcast Feed.

Please click the play button below to listen to this podcast!

Windows in Load Bearing Structures

One limitation of load bearing construction is how much open space you can have in a wall as compared to the overall square footage of that wall. That may be true, but it does not mean that the size and shape of the windows and doors you add to the structure can’t be inspiring and exciting.

For example, a small window can bring in light and add character to a building just as easily as a large one. The key is in the placement and the finish. Be sure to really pay attention to where the window is placed so that the optimum amount of light and view will be gathered. When finishing the window, be sure to flare the interior to allow the most light to penetrate the room.

The placement of windows in a load bearing structure has an advantage over post and beam or other framed examples. That advantage is the fact that the window buck is not placed until much of the wall is already built. This allows the builder to really see what the view will be like with a solid wall in place. Instead of imagining what the room will be like once filled in, one can see it in real time as the window is placed. That way, the exact location is easier to determine when considering light infiltration and view.

Have fun with your windows. Place them properly and let them become a main force in the character of your building. Don’t get stuck in the box, create a new box with as many sides as you want!

Load Bearing Straw Bale Construction

For many years I have expressed my bias about building a post and beam structure over a load bearing structure. Well, the time has come for me to back peddle a bit and sing some praises of load bearing construction. Having built a few load bearing structures in the last couple years, I have started to see the gold they offer.

For starters, they are quite a bit easier to work with when using “unskilled” labor. I say that with all due respect of course and use the term to identify home owners or friends who want to help, but have little or no skills in the arena of home construction. I have found it very satisfying to spend a few days with a bunch of people raising walls for someone’s home. This is perhaps the image most commonly associated with straw bale construction and although that may have caused some damage to the movement in a weird way, it is really fun to build with a bunch of friends.

When building a simple design, load bearing construction can save significant amounts of wood in a home as well. There have long been discussions about the truth of this statement and I can now say from experience that I believe it to be 100% true. The homes we have built as post and beam have used significantly more lumber than those that are load bearing. In today’s world of dwindling natural resources, this is more important that ever.

The speed at which the buildings go up is actually increased as well. A few people willing to work hard can raise an amazing amount of walls in a short period of time. If all of the window and door bucks are made ahead of time as well as the top box beam, the installation of those items is quick and the overall construction time is fast. I was amazed by this fact and really saw it as truth on my third building project this year.

There are more advantages and in truth, there are disadvantages as well; however, I am a true believer in the potential of load bearing construction. It is especially significant when building smaller buildings like storage sheds, studios, cabins, or guest homes. No need to use so much wood on small, simple structures.

Bracing Load Bearing Walls During Construction

When running a one day bale raising workshop on a load bearing structure last weekend, we encountered the problem of complete walls with no box beam to compress them with. The owners had prepared for the workshop, but had not yet built the box beam for the top of the wall as requested. This meant that we would have all of the bales standing, no internal pinning since we would be using external pinning once the box beam was installed, and no box beam.

In other words, there is nothing holding the building up except for the bales themselves and some corner staples. This is certainly not an ideal situation. To make things worse, no one will be able to work on the structure again until this coming weekend and we were forecast to have high winds on Monday and Tuesday.

To remedy the situation, the home owner used long wood braces from the top of one wall to the top of the other and then braced each wall diagonally to the ground. We used 1/2 rebar as “nails” to attach the bracing to the bales. With this simple solution, the walls felt 100 times stronger and have survived the strong winds of the last two days. For a potential disaster, the end result has been quite cool. The box beam will go up this weekend and then the external pinning will be installed along with any corner wire mesh. The space will be sweet when finished and all the troubles we had during the workshop will soon be forgotten and lost in the beauty of the space.