I posted this exact message as a response to a question on the Podcast blog entry. For those of you who read it there, sorry for the duplication. After receiving a couple more questions about how to bale with exposed posts and beams I thought it was worth publishing this under its own heading.
Timber frame is a beautiful compliment to Straw Bale construction and it has been done several times in the past. The biggest thing to be aware of is that traditional timber frame is not cheap. A standard frame house may cost $6-$10 per square foot to frame while a timber frame home runs about $65 per square foot to frame. That is a major difference and the cost adds up quickly. It is possible to build exposed post and beam instead which is much more affordable and less of a specialty framing system. When doing this, a foundation must be poured for the bales out side of the posts or their load must be incorporated into the floor framing engineering.
Another consideration with running the framing on the inside of the bales is how to finish windows and doors and how the roof attaches to the building. Windows and doors are most easily handled by using bucks for their installation, boxes built for the windows that lay directly on the bales (or the floor for doors). By using bucks you can place your openings anywhere in the wall. In terms of roofing, it is always a good idea to have a large overhang (2′ or more) on bale walls. That is made a bit more difficult because the overhang has to cantilever from the inside face of the bales all the way out over them and that creates a weak spot for the roof frame. A simple truss design is a good idea (if post and beam) and the bent design for timber frame can also handle this. It is, however, important to be aware of this design issue before you complete the home design.
Another issue of concern is the plaster on the inside of the home. It will have a tendency to crack at every post if you are not careful. I like to use expanded metal lath (plaster lath) on the back side of the posts that extends out beyond them by about 6-8″ on either side of the post. This has to be installed before the bales. In addition, the bales need to be attached to the frame so more lath can be stapled to the back side of the post and then bent at 90 degrees and stapled into the top of a course of bales. Done at every course, this provides adequate attachment for the bales. The lath that was applied first allows the plaster to have a strong attachment point at the joint between the posts and the bales. A color matched caulk along that joint is a good idea too.
About the Author
Andrew Morison is a specialist in straw bale and green construction. He has shown thousands of people how to build their own straw bale projects through his comprehensive series of instructional straw bale, concrete foundation, and plastering DVDs. You can check these out at www.LearnStrawBale.com..
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September 13th, 2007 at 1:06 pm
Hello.
I’ve signed up for your online newletter and check your blog pretty often. THANK YOU for what you are doing to promote and educate about straw bale construction. I am trying to educate myself as our family dreams of pursuing this in a few more years. We want a house that is “green” and efficient. We also love the style of timberframing, asthetically. What are your thoughts of combining straw bale and timberframing? Do you know of any sources about this that I could look into? We are wondering both about the environmental effects and just the feasibility of combining the two.
THANKS so much.
Katie
September 13th, 2007 at 1:07 pm
Thanks for the feedback Katie. I appreciate it. Timber frame is a beautiful compliment to Straw Bale construction and it has been done several times in the past. The biggest thing to be aware of is that traditional timber frame is not cheap. A standard frame house may cost $6-$10 per square foot to frame while a timber frame home runs about $65 per square foot to frame. That is a major difference and the cost adds up quickly. It is possible to build exposed post and beam instead which is much more affordable and less of a specialty framing system. When doing this, a foundation must be poured for the bales out side of the posts or their load must be incorporated into the floor framing engineering.
Another consideration with running the framing on the inside of the bales is how to finish windows and doors and how the roof attaches to the building. Windows and doors are most easily handled by using bucks for their installation, boxes built for the windows that lay directly on the bales (or the floor for doors). By using bucks you can place your openings anywhere in the wall. In terms of roofing, it is always a good idea to have a large overhang (2′ or more) on bale walls. That is made a bit more difficult because the overhang has to cantilever from the inside face of the bales all the way out over them and that creates a weak spot for the roof frame. A simple truss design is a good idea (if post and beam) and the bent design for timber frame can also handle this. It is, however, important to be aware of this design issue before you complete the home design.
Another issue of concern is the plaster on the inside of the home. It will have a tendency to crack at every post if you are not careful. I like to use expanded metal lath (plaster lath) on the back side of the posts that extends out beyond them by about 6-8″ on either side of the post. This has to be installed before the bales. In addition, the bales need to be attached to the frame so more lath can be stapled to the back side of the post and then bent at 90 degrees and stapled into the top of a course of bales. Done at every course, this provides adequate attachment for the bales. The lath that was applied first allows the plaster to have a strong attachment point at the joint between the posts and the bales. A color matched caulk along that joint is a good idea too.
September 13th, 2007 at 1:07 pm
Hi – having trouble getting your podcast; window won’t load? But thanks for your most excellent blog it’s teaching me a lot of things I want to know for if/when we get to build what we want.
— Leslie, Ruch
September 13th, 2007 at 1:08 pm
Quick Question: Can load bearing straw wall get building permits as easy as post & rail.
–Peter
September 13th, 2007 at 1:08 pm
Peter,
Good question. The answer is no. Post and beam structures are easier to pass through building departments because the inspectors understand the structural elements of the frame a lot more than they do the merits of the bales as a structural system. There is a code in Oregon and other states that allows for load bearing construction, however, you will likely have to do some convincing nonetheless!
July 22nd, 2008 at 6:50 pm
Have you had any experience with Eastern Redcedar as a structural support? I’m wanting to use fresh, debarked timbers as the post in a post and beam strawbale barn frame.
July 22nd, 2008 at 7:11 pm
Cor,
As long as it meets your local codes for structural support, that will be fine…and beautiful!
February 10th, 2009 at 11:14 am
i’m designing a straw bale/timber frame home with an exposed frame. i’m planning on a 4×6 raftered roof with each rafter hanging out 18″ past the outside of the bale wall. i’m wondering if you have any suggestions as to how to join the top of the bale wall to my roof system (notch the bales around the rafters, then what?). i know from past experience that bale walls have the tendency to settle a bit and i’m trying to figure out a way to prevent a gap from opening at the top of the wall. any thoughts would be much appreciated. thank you.
February 10th, 2009 at 11:33 am
Hi Ethan. I suggest you don’t try to notch the bales around the rafters. Remember that the strings will be on top and so that will make it all but impossible to notch the bales. Even if you were to stack on edge (which I don’t recommend), notching is still not the best option.
Build a soffit at the top of the wall that extends down from the roof assembly. The soffit should have a flat surface for the bales to stack up to. The area above the soffit floor is insulated with whatever insulation you are using in the house other than bales: wool, cotton, spray, fiberglass, and so on. The face of the soffit should be covered with plaster board so that when plastering, there is a seamless transition between the bales and the soffit. This is the easiest way to avoid any settling because you can cram the last course of bales in tight to the bottom of the soffit thus minimizing any sag that might otherwise occur. It also give you a channel to run some electrical if you need it. Good luck.
April 21st, 2009 at 5:32 am
Hey Andrew,
I have a friend who plastred behind his exposed posts to limit cracking and for continuity. They used eye bolts to tie the bale structure to the backs of the posts. It was labour intensive for the plasterers to say the least but the finish is fantastic. He and I were talking the other day and wondered about the possibility of attaching masonry board with the plaster lath to the back of the posts. It seems like this would be a little more rigid to cracking and would give a seal behind the post without having to plaster behind. What are your thoughts?
April 21st, 2009 at 5:46 am
Andrew,
Another quick question on window bucks on the bales. Is it better to carry the window bucks to the floor like the doors or is there no difference for crack reduction etc?
Also related to my last querry above, do your DVDs cover exposed interior post and beam techniques as well?
Again…. Great site Andrew, you’re doing great things for demystifying bales.
Thanks!
Pete
April 27th, 2009 at 10:20 am
I like the idea of using plaster board behind the posts along with the blood lath. This would, as you say, make for a rigid installation. Sounds a little labor intensive, but perhaps not so bad in the end. Be sure it is relatively thin so you don’t have to notch the bales around it at every post.
In terms of the bucks, I prefer to carry mine to the floor if I can, again to minimize cracking; however, if they are anchored well to the bales and reinforced with the lath, they would be fine as a load bearing window buck, just floating on the bales.
My DVDs do not specifically cover the system you are talking about.
August 12th, 2009 at 12:48 pm
This is about as close a topic as i could find to my question. I have been designing a straw structure for abour 3 years, and i have yet come to any info on the type i want to use. I am planning on using post and beam but my posts will be approx 6 feet outside the bale wall, this gives us an exceptional overhang, and a wrap around porch space as well. however, it is very difficult to find info for foundations on this type of build. while the post and beam will handle all of the weight of the roof and ceiling, and some of the floor as well (we were planning on interior posts to support the ridgeline, which would also be tied to the ceiling and floor joists). the bale foundation will have to be tied in to the floor joist system and ceiling system as well. We have a 30″ frost depth in our build codes and i really dont want to put down a 2′x2.5′ chunk of concrete. for all the obvious reasons. Is there any input you could give me to help me with this? I would be ever grateful.
October 26th, 2009 at 4:22 pm
That’s a tough one. I would suggest rubble trench technology for sure. I think this is more of a question for an engineer though. You might try contacting Nabil (Nah-Beel) Taha at 541.858.8500. Good luck.
January 18th, 2010 at 6:09 pm
Wonderful posts on straw bale & timber frame. I specialize in Timber Framing and can help anyone obtain thier timber frame dreams. Visit Heirloom Timber Framing at
http://www.heirloomtimberframing.com/
November 28th, 2010 at 2:38 pm
I have also been planning a Post and Beam Strawbale construction and have purchased your entire DVD set and am anxious to recieve your new version of the Post and Beam Infill. Do you recommend a specific book that will get me started in how to Timber Frame? I was just about to push the button on “A Timber Framer’s Workshop: Joinery, Design & Construction of Traditional Timber Frames” but thought that I should check with you first. Also, I absolutely love the idea from Eric above and was wondering if he ever got any farther with his plans?
December 6th, 2010 at 12:53 pm
I don’t have any specific recommendations on timber framing. I have never done the art myself (with my own hands) so can’t really comment on it. Not sure how things went with Eric, I never heard an update.
October 5th, 2011 at 11:19 am
When you say it cost $65/sq. ft. for post and beam – does that include the straw bales and such or is it just the post and beam frame? Also, is that using kiln dried wood? What about using rough-hewn lumber?
October 10th, 2011 at 5:47 pm
This is just the timber frame cost. Not sure how the lumber differences would influence the cost. I don’t do enough work with custom timber frame to answer that question well.