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32 Responses to “A Quick Word on Wall Height”

1. Trevor Says:
   January 15th, 2008 at 4:27 am

   here is an example of a 2 story load bearing strawbale home that was built in Canada http://www.dna.ca/strawbale/ most i have came accross are 1 story and a loft but this one seems to be 2 full stories

2. Andrew Says:
   January 15th, 2008 at 7:23 am

   Thanks Trevor. This is cool. In Oregon, and most of the other official accepted building codes I have seen, load bearing walls are limited in height which is why you mostly see single story or single story plus a loft. I have not had a chance to read this entire site, so I am not sure how they got around that requirement. Thanks for posting it though and I will try and read it through when I get a chance.

3. Marlene Says:
   January 18th, 2008 at 9:03 am

   Why are the bales laid flat? I would have thought they would have greater insulation value stood on end.

4. Chadwick Mckellar Says:
   January 20th, 2008 at 7:28 am

   Does anybody have “data” on nylon strapping for load bearing wall. Other than post and beam how are we going to get regional building dept. to OK a load bearing wall where the rafters are some how directly fasten to the foundation. What happens to strapping and their clips in 80 to 150 years down the road. That’s what regional is asking…

5. Andrew Says:
   January 21st, 2008 at 4:41 pm

   Marlene,
   The main reasons for laying the bales flat is for ease of installation. Bales on edge are less stable in load bearing construction and impossible to notch around posts in post and beam construction due to the twine. Additionally, the thicker the bale, the higher the R-value as most studies show it as a function of bale width, i.e. R-Value per inch.

6. Andrew Says:
   January 21st, 2008 at 4:43 pm

   Chadwick,
   I use Cordstrap (www.Cordstrap.com for my load bearing strapping. Their website is a great resource. In general, if the webbing is not exposed to sunlight, it will last forever…..(that’s a theoretical word when speaking to buildings of course).

7. Steve Petersen Says:
   January 26th, 2008 at 3:33 pm

   Andrew whic type of stucture would you build if you lived in Colorado Load Bearing or fill-in and why. Thank you

8. Andrew Says:
   January 26th, 2008 at 9:38 pm

   Steve,
   It depends on what your criterion are. If you want a flexible design, then go with in fill. If you want a simple design with less framing and “skilled labor” then go with load bearing. For me, the design dictates the style of construction.

9. joe w. Says:
   February 12th, 2008 at 6:51 pm

   Andrew? im confused on how large a weight bearing home can safely be with an open floor plan? 20 by 40? 25 by 50? and also, if i started with say an 800 square foot house,
   could i build an addition onto it by pouring 3 side foundation and use the existing wall?

10. Andrew Says:
    February 13th, 2008 at 7:36 am

    Joe,
    A good rule of thumb is to not exceed unsupported wall runs (no intersecting walls) for more than 20-25 feet in load bearing construction. If you want to go further than that, you should install a buttress wall perpendicular to the bales. It can be short and even made of bales interlocked with the main wall. The point is you need something to stop the wall from falling over on long runs.

    You can certainly build an addition as described above. The key is to plan ahead so you don’t run electrical or other “unforgiving” materials in the area where you plan to expand. In fact, placing a door in the wall or a large window where you eventually want to expand is the easiest way to ensure that space is available for the addition in the future.

11. joe w. Says:
    February 13th, 2008 at 8:25 am

    Andrew, thanks for the quick response. in my search’s i have found a few weight bearing homes that are 2-3000 sq. foot. how is that possible or is there clearly a risk there being taken? also i have watched you video clips and will definately be ordering your dvds. Thanks for helping us all and spreading the word on sb!

12. Andrew Says:
    February 13th, 2008 at 8:42 am

    It is okay to build large load bearing homes as long as certain issues are addressed. For example, you can build a large great room if desired as long as there are intersecting walls to control out of plane deflection (what we talked about above). You can build tall walls as long as they do not exceed the width to height ratios for safe stacking. You can build a loft/second story if the roof pitch is steep enough and the wall heights are maxed out. Anything is possible with enough time and money! That is what I hear all the time from my engineers. That said, I think anything is possible (to an extent) as long as the right planning is in place and the detailed execution of that planning is employed.

13. joe w. Says:
    February 20th, 2008 at 11:37 am

    Andrew, i am trying to learn about maybe using 4 by 4 post and beam. from what ive found so far, it seems you only have to place the post 6 to 8 ft. apart besides around doors and windows, so the use of wood doesnt seem like it would be excessive as normal 2 by 4’s having to be 16 inch centers. and using this technique it seems like i would not be nearly as limited on my home size. can i get your opinion using this method?

14. Andrew Says:
    February 20th, 2008 at 4:49 pm

    Joe,
    Let me start by saying I am not an engineer and so cannot recommend a spacing for the posts. Your theory is one that is debated quite often. Some people believe that a post and beam house saves wood. Others say it is a wash between the two. Still others say that a post and beam house uses more wood than conventional framing. The reason for this disagreement is that some home designs allow for wide spacing of the 4″x4″ posts, and small beams while others call for close spacing of larger posts, say 8″x8″, and larger beams, say 8″x12″. The house with simple engineering will use less timber than conventional framing; however, the latter design would actually increase the volume of wood on the site over that of a conventional home.

    As you can see, much depends on the design and engineering. My belief is that on a simple house, with proper construction, the amount of wood used is slightly less in a post and beam house; however, I do not believe that the difference is that large. I have never taken the time to calculate wood volume on the same house built two different ways, but that would be interesting information to see.

15. Ruth Says:
    February 22nd, 2008 at 1:34 pm

    Marlene,

    In my research I have found that the R factor is higher if you stand the bales up and not lay them flat. This is due to the air not being allowed to “flow” through the hollowness of the hay. Bales laid flat have an R factor of 1/5 per inch, where as bales stood on end have an R factor of 2 per inch. Is this right, Andrew?

16. Andrew Says:
    February 22nd, 2008 at 3:33 pm

    There is not very solid data for the R-values of straw bale walls. If you consider the theory that laid flat is 1.5/inch and on edge is 2/inch then the values would be (in order) R-27 and R-28. The difference is almost immeasurable. In the field, however, the bales perform much closer to R-40 in my opinion.

17. joe w. Says:
    February 24th, 2008 at 6:10 pm

    Andrew, you mentioned to watch for wall deflection on an open floor plan. i would like to build a post and beam straw bale using 4 by 4’s besides at the doors and windows of course, and i want to put lofts at each end so the flooring on the ends will hold the walls solid, but if the house is say 25 by 45, then the center great room will be approximately 23-24 foot open space. worrying about roof to wall deflection, could i use 2 6by6 beams about 8-10 foot apart to stabalize this outward pressure and hopefully give it some character. there are also no permits, codes, or inspections in this county.

18. Andrew Says:
    February 25th, 2008 at 7:45 am

    Joe,
    I hesitate to give structural advice because I am not an engineer. That said, the deflection in the walls can be caused by more than just the roof loading. Even string winds can play a role in deflecting the walls if they are unsupported. You may want to build an intersecting buttress out of bales to shore up the wall run, or consider moving to a post and beam design which will handle the deflection within the structure. It is only load bearing that runs a big risk in this situation as a structural frame can be designed to handle the loads. With the inclusion of lofts at both ends, you may as well build P&B anyway.

19. Hank Carr Says:
    February 25th, 2008 at 5:33 pm

    Hi, folks.

    I’m the owner/builder of the house Trevor referred to. Our house is in fact a full two storey. The first floor walls are 10′ and the second floor walls are 8′. The great room walls run 19 to 25 feet tall unsupported from the north east corner to the middle of the south wall for over 70′.

    There are very few (technical) limitations to what you can do with straw bales though there are LOTS of online mythological limitations. In Ontario we’ve ceased to be limited by the mythology and are now building large, beautiful homes in many sizes and shapes. We’ve got government subsidized commercial buildings, a circular 12,000 square foot agricultural building, a 40′ diameter two storey load bearing home. You name it, we’ve got it.

    I highly recomment the OSBBC website:

    http://www.strawbalebuilding.ca

    as well as our straw bale portal:

    http://www.sbportal.ca

    Make sure you check out the FAQ (the largest and most complete on the web.)

    Hope this helps.

    HAnk.

20. Andrew Says:
    February 25th, 2008 at 9:08 pm

    Hank,

    This is great information. Thanks for putting it out here. I am curious as to how the unsupported wall lengths and load bearing walls heights are designed and functioning. What criteria was used to build that far “outside of the box?”

21. joe w. Says:
    February 26th, 2008 at 9:44 am

    andrew, whats the difference in insulation values for an 18 inch bale versus 24 inch bale??

22. Andrew Says:
    February 26th, 2008 at 10:48 am

    Joe,
    There are many differing opinions on the R-value of bale walls. If you agree that an 18″ bale will provide an R-40, then a 24″ bale will proved roughly R-53. Perhaps most important is to note that after a certain level, the number does not matter because the value is so darn high that the law of diminishing returns starts to kick in. In this rule, even though you add more insulation, the affects of that insulation is felt less and less as the number climbs. Unless you live in a drastic climate (really hot or really cold) I suggest you stick with 18″, two string bales. They are much easier to handle and proved excellent insulation and sound proofing.

23. Hank Carr Says:
    February 27th, 2008 at 3:53 am

    Hi, Andrew.

    Our building was engineered by Dr. Kris Dick or Building Alternatives in Winnipeg, MB and the University of Manitoba, Winnipeg.

    We used 19″ 2-string bales stacked flat and the build-plaster-build-plaster method to raise the tall walls. Our first floor walls were stacked all the way around the house. The top plate goes all the way around the first floor including the long wall of the great room. Two coats of plaster were applied to the inside of the first floor walls and one to the outside. We then added our second floor deck 3/4″ of the way around the house and stacked the second floor walls. Our decks were designed to be as thick as a single course of bales so we just had one extra course where there was no deck in the great room. Once the second floor walls were ready the plaster crew applied one coat to the inside of the second floor wall and one coat to the outside. They then did the second coat on the second floor inside and a second coat to the entire outside of the building.

    Our top plates are 2×6 ladders with 2×8s on the outside (2×8, 2×6, 2×6 blocking, 2×6, 2×8) with 1/2″ plywood across the top and bottom. The bottom plywood is narrower to fit between the 2×8s. The corners were designed for maximum strength. The corner plywood was cut from full sheets and overlapped 4×8 in one direction and 8×4 in the other. We also added large Simpson strong tie straps around the great room corner.

    Here in Ontario straw bale construction is pretty well accepted. There are still lots of people who don’t know about it and it isn’t nearly as common as I would like but we don’t consider it to be weird or experimental anymore. We don’t have buiding permits being turned down and our performance based code and liberal Building Code Commission have made things much better for bale builders. We’re even got three storey post and beam infill straw bale construction in one case.

    We hope to have something really exciting to announce in the next couple of months.

    Hank.

24. Andrew Says:
    February 27th, 2008 at 12:32 pm

    Hank,
    Thanks for the details. That sounds pretty cool. I am concerned about the way the walls were loaded though. I am sure the engineer addressed this issue, but it doesn’t make any sense to me to apply skins to a load bearing wall and THEN load it with the weight of a second story. It would seem like you are asking for uneven settling this way. I get that the skins, together with the bales, provide for the strength of the walls; however, I would think the load should have been applied first to fully compact the bales and the skins then added to lock everything in place. Why the change of sequence?

25. Hank Carr Says:
    February 27th, 2008 at 1:08 pm

    Hi, Andrew.

    Kris Dick is one of the worlds foremost experts on straw bale construction. His research has been peer reviewed and widely published. It is in large part due to his work that we no longer consider straw bale construction experimental here in Canada. It is a well understood though under utilized method of construction.

    He did the work on our house in 2001, before the OSBBC and before the recent wide acceptance of straw bale construction here in Ontario. He was VERY cautious when he engineered our house. If we had it to do over we would probably have reduced the top plate size. We’re using a much smaller

    Straw bale walls function as structural insulated panels (SIP) with the skins bearing the load and transferring it from the top plate to the foundation. The straw insulates and stabilizes the panel. The straw has the same function as the Styrofoam (or other foam) in a commercial SIP and bears just as much of the load. IT is easy to find evidence of this fact in the wide acceptance and almost 100% use of the Ontario Light Frame method of construction where the bales are stacked into a light frame (which supports the roof during construction but is not rated for snow loads.) The plaster is assumed to carry the load of the building after the walls are plastered WITHOUT any pre-compression. It is this fundamental concept that prevents builders in many places from moving out of the fringe, experimental technology realm and into the mainstream of the construction industry.

    A good reference on this subject is CREEP IN BALE WALLS by Dan Smith.

    If you can’t find it anywhere else you can get it from the OE strawbale portal:

    http://www.sbportal.ca

    Follow Resources, Documents or click here:

    http://www.sbportal.ca/resources/documents.shtml

    As a matter of interest, straw bale construction is so well accepted here in Ontario that I have been invited to be a presenter for a technical session on straw bale construction at the Ontario Building Officials Association Annual Meeting and Training Sessions this year with Tina Therrien and have received independent invitations from the Building Department, the Planning Department, and the Housing Department of the City of Ottawa to teach them about straw bale construction. I also received an email from a building official in Alberta the other day asking about cracking and moisture performance of bale wall systems for an inspection he was doing.

    Hank.

26. Andrew Says:
    February 27th, 2008 at 2:51 pm

    Hank,
    This is really exciting. Thanks for sharing it. It makes total sense, I simply thought that pre-loading would be a good idea. I am excited about this and plan to explore the sites you listed for further input on the subject.

    Andrew

27. Hank Carr Says:
    February 27th, 2008 at 5:59 pm

    Howdy, Andrew.

    Pre-compression of load bearing straw bale walls serves an important function. If you don’t pre-compress your walls settle (creep) over the first 8 weeks. That’s the 8 weeks in which you’re trying to put on mesh (if you’re using it) and stuff and stitch your walls. You’ve also got your top plate on and levelled. When your walls creep once the mesh is on and the top plate is on your mesh becomes loose and your top plate goes out of level. If you pre-compress your walls then leave them for a few days and re-compress and level them they’re going to move a lot less while you work on them. If you could get your walls up and stacked on the same day pre-compression would be a complete waste of time (if you’re using cement plaster, of course with a nod to Dan Smith.) Of course, no one actually does that (except on workshops.)

    I’ve given up banging my head against the lists like virtually everyone else in Ontario. Since the lists are all about crazy speculation and wild experiments in making buildings more complicated and more expensive they are really irrelevant to straw bale construction in my neighbourhood. What that means is that no one ever hears about the great work we’re doing up here.

    Ontario straw bale construction is all about simplicity. We’ve boiled it down to its essence then simplified and standardized. We avoided the biggest mistake that many places have made by intentionally avoiding codifying straw bale construction. That has allowed us to experiment until we got it right. We’ve also this year overturned the one bad ruling of the Ontario Building Code Commission from 1999 and have gotten two 100% pro-straw bale construction rulings.

    There is an absolutely amazing amount of mythology associated with straw bale construction. Everything that anyone has ever said you can’t do with straw bales we’ve done. Many of the things that they say you have to do we don’t do any more. It is incredibly frustrating to me to have people call me looking for advice who say “I’ve been doing a lot of research on the internet”. The first thing I tell them is “forget everything you’ve read”. We’ve been saying for years that lime plaster over earthen plaster won’t work. It’s only this year that someone leaked the fact that the Good-old-boys Straw Bale Network has been secretly discussing that fact that they had come to the conclusion that it doesn’t work. Unfortunately, that hasn’t been reflected on most pro-earthen plaster websites. Neither have the very damning calculations about the true carbon cost of lime plaster. No one wants to know the truth. So what do we do?

    We go on building. 100 square foot sleeping cabins to 12,000 square foot stables. 850 to 7000 square foot houses. Full commercial rated buildings that were government subsidized. One to three storeys. Edge and flat stacked (even two storey edge stacked load bearing.) Every foundation system you can imagine. Every plaster you can imagine. Every shape you can imagine.

    Once you get your head around, once you truly embrace the structural insulated panel nature of straw bale construction and really accept that the system works you can do anything.

    There are some buildings up here that would absolutely blow your mind.

    One last note…there is some spectacular work being done with straw bales and plaster at Queens University by our friends Stephen Vardy and Colin MacDougall. Some of their early work is on the Documents page on the SB Portal website as well. That reminds me that I should probably send them off a note asking for their latest results.

    I’m glad you’re excited about this. It is really liberating to decide to stop worrying about what the lists say you can’t do and start doing what you really wished all along that you could do.

    Bale on!

    Hank.

28. Andrew Says:
    February 27th, 2008 at 7:18 pm

    Yeah, the SIPs model makes total sense and it sounds like we both agree about pre compressing the bales. I think the way I wrote it may have confused what I was trying to say. I hope I can help move this information forward. Once I have found the time to read more about this, I will try and post some stuff on this site to help get the word out.

29. Hank Carr Says:
    February 27th, 2008 at 7:26 pm

    I got that you got what I was saying. I was just evangelizing for the others who might read this. That’s what I do.

    I’ll get off my soap box now.

    Take care.

    Hank.

30. joe w. Says:
    February 29th, 2008 at 9:11 am

    here is some info. on strawbale home grants in missouri. sounds like it is a limited study grant available to the first 10 owner/builders
    The plan was to inform residents of two counties in Missouri, Ozark County and Douglas County about the benefits of strawbale construction. Each house would be built by the homeowner, utilizing their own labor, donated and hired labor, under the council of a specialist hired by Top of the Ozarks. The specialist would provide the information to potential participants, guide them through the maze of forms for the EPA and HUD, inform about the building codes required by the program and other items as needed. I live with the specialist, Richard Lorenz and I can tell you that he has dug and does dig around through all sorts of research for the benefit of the program and deliver it to the participants or potential particpants so they can do the very best job on the first time around. He makes presentations at various groups using a PowerPoint show with handouts and a much larger PowerPoint program on a CD. The CD which he sends to all who ask for it, includes further information about design, methodology and pictures of successful structures.

    A straw bale construction code has been developed in Oregon and in California. These codes, along with the latest UBC will be applied to the homes for them to be eligible for the grant. The codes were developed from experience in other parts of the country where straw bale homes have been going up and either succeeding or failing. There are several successful structures in Missouri — to the point of having a loose registry. A resource and research group, Dancing Rabbit Ecovillage.near Memphis, Missouri has been trying all sorts of different methods and have decided there are things they would do differently on future projects.

    The intent is to have 10 homes built in three years which are eligible for a $15,000 grant toward materials and which presents a fine equity in the home.

31. Bobby Palm Says:
    March 9th, 2008 at 12:38 pm

    Fist I want apologize for I may be misunderstanding the full extent of the load bearing, compression concepts as discussed by HANK CARR. I am very disturbed by the concept of plastering w/o precompression and the thought of plaster carrying the roof and snow loads as bales will settle with time and weight. I have biult for over 35 years with steel, cmu’s, concrete,frame, log, timber frame, ( post and beam ], rammed earth (tire homes), stone masonry, brick domes, strawbales. I have combined all of these mediums successfully, but the first thing I always have to consider is thier purpose, application, relative strength, short & long term expansion and contraction and the local environment, desert, heavy rains or snowloads high winds, I am a renigade when it come to codes but experience has taught me to respect them. I was also on the strawbale committee in N.M. 10 to 15 years ago that helped strawbale get going here. I can understand Hanks carefree atitude for experimentation but it sounds perhaps a little careless. I respect and appreciate your handling of all of his feed back and definitely share your concerns abot compreeion and or creep and the comments on latterally supported walls are very well founded. It sounds like lots of peole have gotten away with murder on some experimentation which is good to push thinking out of the box but I have a feeling many will learn some ugly lessons in the long run and because of human pride most won’t hear about the failures and mistakes. Andrew you are doing a phenomal job keep it up. Bobby Palm

32. Hank Carr Says:
    March 10th, 2008 at 2:29 pm

    Hi, Bobby.

    None of what I posted was the least bit carefree. In fact, unlike most of the unfounded and unsupported opinion that you read on the internet it was based on well documented testing. You can read Dan Smith’s testing report here:

    http://www.ecobuildnetwork.org/pdfs/Creep_report.pdf

    By far the biggest impediment to the broad acceptance of straw bale construction in most locations is the continued repetition of mythology, wives tales, and wild speculation which has been repeated so often by so many that it is now taken as fact. Unfortunately, it is often the proponents of straw bale construction who perpetuate these myths to their own detriment.

    Hank.

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