SB: Proposed Nebraska Style

[Athena and Bill Steen <absteen@dakotacom.net>]

Title: Proposed Nebraska Style

Ok, Ben, one more question.  When you achieved the compression figures below, did you use the come-along or the vice grips with the metal fence post?  I can easily understand achieving that amount with the come-along, but on paper the other looks kinda iffy.  We used come-alongs or fence stretchers in Mexico quite a bit and for walls that were 8 courses high we were able to take 5 inches out of them on the average.  However, we were using 1/4 inch wire, so breakage of the wire wasn't an issue.  And that was only for a non lb building.  We've done levers, ropes and just about everything imaginable, so I have trouble seeing how the lever will work effectively.  But maybe!

As for bales on edge, I agree, that initially they compress little, but over time they will.  It is the only time that I saw a building settle enough (little roof load) that it actually popped the plaster off on top of the exterior pins.  They were sitting on the foundation and so as the bales settled, they pushed up through the plaster.  So anyway, this settlement issue is one of the things that really bothers me about building two storeys on edge.  Initially, you won't get much compression and then once the roof load is applied you are going to get further settling.  The question is when does that occur.  Before the stucco has been applied.  Does it begin and start happening as the stucco is curing and hasn't reached full strength?  Does it happen later.  And then all this has to be considered in light of the fact that you don't have anywhere near the plaster/straw bond as when the bales are laid flat.

Then there is one more detail that concerns me and it applies to any two storey structure as well as single storey buildings with wood floors.  It seems to me that having your box beam or whatever is being used to connect your floor joists interrupting the continuity of the bales in the wall is potentially a problematic point.  In my mind what happens is that you insert into the middle of the walls another material (wood - papered and wired) that simply gets covered over with cement stucco.  Yes, I know it is a common practice, but it doesn't mean that it isn't one we shouldn't take a further look at.  In wood construction it is not necessarily a problem as there is continuity in the sheathing, paper, etc. all the way down the wall.  Breaking it the bales with wood creates the scenario where there are two different materials, each reacting to thermal stresses in a different way with different rates of shrinkage etc.  Is is a cause for structural failure, of course not.  But.....it is a point that could experience cracking, resulting in moisture intrusion, air leakage and the like.  I know that John Straube sometime back told me that he thought it one of the worst aspects of SB buildings with wood floors and that he felt the potential complications down the road were potentially serious enough to avoid the use of this kind of detailing.  (That ought to stimulate a little discussion.)  So if I were going to build a two storey building, I would try to get continuity in the bale wall surface all the way up on the exterior.

Bill



> From: Ben Polley <info@harvesthomes.ca>

> 
> Hi Bill,
> 
> I don't recall how many inches bales set flat compressed on any project on 
> which I worked - since bales flat has always been more conventional, I guess 
> it doesn't stand out.  But I would say from memory probably 2-4 or 5 inches 
> over seven or eight courses (nominally 8-9 feet overall).  
> 
> The first bale-on-edge building that I worked on was a 14 x 14 sleeping cabin 
> built as part of a workshop 3 years ago.  It had seven courses of two-string 
> bales on edge providing a nominal 10' 6" height (the environmental learning 
> centre at which it was built wanted to stack 3 sleeping bunks along its 
> walls, hence its height).  Granted this had short linear wall length overall, 
> (14') but I recall the walls were naturally only 1" off-level in any 
> direction (prior to any natural settling).  We then applied compression using 
> the same tools (1 tonne come-along and fence stretchers) and found that we 
> could achieve little compression.  How much exactly I don't recall but I do 
> remember that shortly after achieving level (so not much more than an inch or 
> two if that) instead of the bales compressing under the distributed force of 
> the tensioned top plate, the top plate (continuous 2x6 beams with what I 
> think were 2x4 cross members and 1/2" or 3/8" ply sandwiches to create a box 
> beam) began to bend at the points of loading.  The compression wires were 
> installed approximately every 2 feet (to give everyone a chance to try their 
> hand at the cumbersome come-along set up) and I do remember that one did 
> break (after I accidentally nicked it with a pair of pliers while talking 
> with my hands.  Don't stand near me when I'm explaining things to a group.  
> Or maybe, just take potentially dangerous instruments from my grip!)
> 
> This example has been typical of the bales on edge walls in which I 
> participated. I do remember one exception though -> a box-beam type house 
> (Rob, what more appropriate technical term did you use for this) that 
> incorporated bales on edge did experience settling (in terms of total creep) 
> beyond what I had ever achieved through mechanical means.  Some of those 
> walls saw about 3" of compression in the several days before the required 
> wire mesh went on and stitching occurred, similar to what we often see and 
> expect with bales flat over the same time in the same design.  The gap was 
> then stuffed and wire installed/stitched/walls plastered.  A qualifier on 
> this result may be that these walls incorporated many retied and even rebaled 
> shorter bales due to the sometimes limited spans between box-posts (which 
> were each the full width of the wall similar to John Kingsley's posting).  
> Perhaps these short and part bales did not have the same overall density as 
> the full bales?  
> 
> These are my observations.  I'm curious what people make of them.
> 
> Cheers,
> Ben
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