Thursday, November 9th, 2006 | Popularity: 12%
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.
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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.
Popularity: 12%
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Andrew Morison is a licensed contractor specializing 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 http://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!