Many people have recently asked me about landscape walls. As a result of those inquiries, I’ve drawn up a cross section of a landscape wall and rubble trench foundation for you to check out below. This is a basic design that can be used in most locations. Some building departments allow for rubble trench foundations within the codes while others are less accustomed to them. Be sure to discuss the potential to use this design before you commit to the design. You may need to make changes to the system or simply educate the building officials around the effectiveness of the rubble trench design.
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I’m open to feedback on the design. If you think there’s a better system, let me know. I always like to hear how other people do things. As a builder, I always spent time visiting other contractor’s job sites and talking to them about how they did things. I’ve learned a LOT by talking to others and I continue to learn this way today. One detail I often put into landscape walls in wet climates is a metal wall cap. The caps are custom made by the local metal shops (those who fabricate metal roofing are best) to fit over the top of the finished wall. You need to provide some anchoring points for the caps within the wall, but that’s not shown here. Simply let in a 2x at the top of the wall so that the bottom edges of the roof cap can hit it during installation. be sure to install the wood nailers before the mesh so that the mesh can lock them tightly in place. Get the wall cap in a color that matches or compliments your plaster and you’ll barely notice it’s there (or you’ll see it as an asset to the design).
One point around landscape walls and moisture. It’s really not that big of a deal if the bales get wet and ultimately rot out. That matters BIG TIME in a house, but a wall is just that, a landscape wall. The bales are not acting as insulation, they’re basically acting as forms for the plaster. Once the mesh is properly installed and you add 1 1/2″ of plaster to each side of the wall (all the way up and over actually), the bales can rot out without the wall collapsing. Of course, the overall strength of the wall is better with the bales in place, so protect them as best you can. Just don’t loose sleep over water getting in through a failed washer on a screw that attaches your wall cap. The wall will be fine!
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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May 11th, 2010 at 8:35 am
Hi,
The wall appears to be a conventional strawbale wall.
My question is how would you keep the wall from being pushed off the rubble trench in a high wind area? It may no happen quickly, but over time the wind force could “walk” the wall off the rubble.
Thanks,
Ted
May 11th, 2010 at 10:55 am
Hi Ted. The mesh that is attached to the toe ups, pulled tight over the bales and then attached to the toe ups on the other side of the wall keep this wall locked in place and attached to the foundation. If the wall were taller and in a high wind environment, then I would use buttress walls to strengthen the “out of plane” direction of the wall. The location and size of those buttress walls would depend on the wind speed and wall height.
June 1st, 2010 at 9:45 pm
Hi Andrew,Ted,
I have plans to build one myself, and will finish it with a ceramic tiled “mini” cambrel or dual slope roof to protect the bales for rain and snow. In order to do just that I need a top beam which (as I learned on one of your posts) can tie down the bales to the toe ups. That should be enough to protect from strong winds also, don’t you think?
Rudy
June 2nd, 2010 at 5:53 am
Hi Rudy. Yes, that would be fine.
Andrew
September 24th, 2010 at 10:59 pm
Andrew, now that it’s much too late I’m wondering about rubble-trench foundations for strawbale houses. Are those practical in this earthquake Zone C (or is it D?) area? I specified them when we took the plans to the engineer, but he ignored the idea and specified a conventional concrete foundation — about 25 yards’ worth!…Jerry
September 25th, 2010 at 8:54 am
They can be if they are designed properly. They need additional details to resist uplift. It can be done for sure, but it takes the right person designing it and a willingness to not take the “standard easy way out.”
March 14th, 2011 at 6:25 am
Hi Andrew,
Santa Fe this Spring (2011)! It is just what I want to do and where I am!! Could you email me information on registration? Thanks!
March 14th, 2011 at 8:46 am
Hi Beth. Thanks for your email. I have some bad news though…the workshop in Santa Fe is not happening as the host’s mother has gotten very ill and so the host will need to focus her efforts on helping her. It’s a sad situation for everyone, most notably the host and her mother. I wish them the best and hope that a quick recovery is possible. I apologize for the misleading information ion the blog post. I will have to remove that. Thanks for alerting me to it.
I am just about to secure a deposit for a workshop in Colorado, so hopefully that is something close enough to you to replace the Santa Fe class. It’s not a landscape wall class, but a full house workshop. I am also trying to find a way to do a landscape wall workshop in Montana. The timing is the hard part right now. Stay tuned to http://www.StrawBaleWorkshops.com for updates on workshop dates and locations.
August 30th, 2011 at 2:17 pm
I live in Austin, TX and my soil is mostly clay. Do you think the foundation needs to be this deep?
August 30th, 2011 at 2:28 pm
I’m not an engineer, but I seriously doubt it. Deeper foundations are typically due to frost lines. That said, if you need to get below the clay to noexpansive soils, it may be necessary. You are best to discuss it with a local soils engineer or ask builders in your area what a standard foundation is. Good luck.