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Where Does Cordwood Work?

Rob Roy is Director of the Earthwood Building School, which has specialized in cordwood masonry instruction since 1980. Rob and his wife, Jaki, have built four innovative cordwood homes for themselves since 1975, including the Earthwood home where they have lived for over three decades. Earthwood is a 2400 SF two-story round, load-bearing cordwood home, earth-bermed and earth-roofed. Details of construction are in Rob's Earth-Sheltered Houses (New Society, 2006) and Cordwood Building: The State of the Art (New Society, 2003) two of fourteen books he is written in the alternative building field. Rob and Jaki have taught cordwood masonry in Earthwood Building School all over North America, as well as in Chile, New Zealand, Australia and Hawaii. They have helped scores of owner-builders with their cordwood projects, including homes, saunas and outbuildings. Earthwood has produced a 3.25-hour DVD on cordwood construction, which, with his books, can be accessed through the Earthwood website, or on the Cordwood page here. Rob is considered to be one of the leaders in the field of cordwood construction and earth sheltering. He does individual consultations at a flat rate of $75/hour, but answers questions here without charge. See also Earthwood Facebook. In July of 2015, Rob and Jaki, will be host the 5th Contintental Cordwood Conference at Earthwood CoCoCo/15, returning the conference to where the first one was held in 1994. Go to Earthwood Building School for information.

Questions and Answers

Q: Is cordwood building a good idea in Florida? My concern is the high humidity here.

A: I don't see a problem with building a cordwood home in Florida. They have been built successfully in tropical Belize and in West Columbia, Texas, which, if anything, is even more humid. Also, there are two very successful cordwood homes in Adel, GA, just 40 miles north of the Florida state line. One is over 20 years old and the other about 15 years old. Wood species selection would be the same as any other climate. I would incorporate a termite shield into the foundation, and use a good overhang or wrap-around porch, particularly on the windward side of the building. Do not treat or seal the log-ends, but definitely take the bark off, as powder post beetles love to get between the bark and the outer layers of the wood.

Q: Just recently I have come across the cordwood technique for home building and must say that it is a real and exciting opportunity for me, as obtaining 'cordwood' is not a problem for me here in Iowa, especially the types of wood preferable for construction. I have read many of the Q&A sections regarding construction in various parts of the u.s. and haven't come across one from Iowa yet. Are there any cordwood homes that you know of here? Will my state allow them as per codes etc.?

A: I cannot direct you to any recent cordwood masonry buildings in Iowa, but there is a historical connection. Writing in Cordwood Building: The State of the Art (New Society, 2003), Professor William H. Tishler says, at page 6: "At least one building, the Norris Miller house (now listed on the National Register of Historic Places), was erected in the Decorah area of Iowa and re-erected by the Norwegian American Museum of Decorah, Iowa, in the early 1980s." We have had students at our cordwood masonry classes from Iowa, but, so far none of them have reported back on their projects. Nearby Wisconsin is probably the hotbed of cordwood construction in the U.S., and has been for well over 100 years. Iowa has favorable woods, as you have said, and also a good climate for cordwood masonry. There is no reason I can think of not to go for it where you live. The book cited above, available above, also has four articles concerning code issues that might be useful on the permitting process. The old building at the museum might be worth a visit, too, although, in general, modern cordwood buildings are far superior in terms of appearance and insulation than the buildings of 100 years ago.

Q: I know from past studies that cordwood and masonry are ideal in the northern part of our continent. I moved from the Yukon, Canada to Durango, Mexico. The climate here is semi arid and very hot for an old polar bear like me. I have seen the advantages and disadvantages of adobe and stucco. I have repaired stucco but it is a never ending job. I want to build a round cordwood home here. Do you foresee a problem building one here in a dry, hot climate?

A: No building system, "natural" or otherwise, is completely without its problems. As a former polar bear, you can appreciate that an igloo eventually melts. Cordwood masonry will not melt in the hot Mexican climate, but you can expect that the logs will get very dry, and check and crack quite a bit. However, this would not deter me from building with cordwood masonry in Mexico. I would be inclined to stick with mortar (as opposed to cob), so that I could easily apply a flexible log chinking product (such as Log Jam by Sashco Industries or Perma Chink) to the mortar joints after the logs have done their shrinking. This should eliminate the "never-ending job" which you spoke of. Complete log-end shrinkage might not occur until a year or two after the home is built, though, so don't be in a big rush to apply the chinking. It is a time-consuming and expensive job that you will only want to do once. Do a Google search to get info on various log chinking products. Be sure to apply a thin coat to the entire mortar joint, not just the spaces around log-ends. Your wall will look great. Finally, during the masonry process, leave your log-ends sticking out a good quarter inch proud of the mortar matrix, so that there is room to apply the chinking. This also makes it easier to apply the material, as the log-ends will guide your brush.

Q: I'm from Quebec, Canada.. I really want to build my green home... but is it kinda hard to choose the good material. Where I'm from, it gets really hot during the summer and really COLD during the winter...On the land that I'm buying, there is only forest and one little river beside... Of course, I wana be sustainable, no electricity from the outside... I gonna make my own... anyways, if you have an idea of what could I use for material, tell me; that would be appreciate !

A: (Kelly) From your description I might suggest that you investigate using the cordwood technique for your walls, since you have forests that could provide the short pieces of wood necessary. Cordwood is naturally quite insulating against the cold and the heat, does not require maintenance over time, is pretty to look at, easy to construct, and can be done to satisfy most building codes.

Q: How does cordwood construction hold up in rainy climates like the pacific northwest? Does getting log ends wet cause a lot of expansion and contraction?

A: About 20 years ago, I saw one cordwood home on the wet side of the mountains in Washington. At the time it was about 50 years old, and the walls were still in good condition. George Adkisson built a fine cordwood home on the very damp humid Gulf Coast of Texas. It seems to be doing nicely with no problems. He has written a chapter about his home in my Cordwood Building: The State of the Art (New Society, 2003). He put a 10-foot "Texas porch" all around the building for protection. In the climate you describe, I would take extra care in building under cover (within a timber frame with the roof on), use a good overhang of at least 24 inches, and keep the cordwood at least a foot clear of the ground. Sometimes our walls get soaked from a driving rainstorm. But they dry out again because of the great breathability of the log-ends. We have not had a problem. It is quite possible that our log-ends undergo a greater variance in expansion and contraction than log-ends in a constantly damp climate.

Q: Since I live in the great white north I was wondering if it is possible to carry out construction of a cordwood home during winter months?

A: I know of a guy who built a 40-foot diameter round cordwood building in Ontario about 25 years ago. He built a tent of 2x4s and translucent 6-mil plastic and heated it with one of those salamander propane heaters. The project was a success, but, even though he used white cedar, probably the most stable of common woods, the log-ends still swelled quite a bit because propane heat is very moist. After a year of living in the home, with dry wood heat, he had to caulk around all the log-ends with a couple of crates of acrylic caulking. Nowadays, we advise the use of a flexible log chinking product for that purpose, such as those made by Log Jam (Sashco Industries), Perma-Chink, and Weatherall.

Q: We are planning to build a cordwood home here in south mississippi about 50 miles north of the gulf coast. I was wondering if we would have special problems with a cordwood home?

A: It is possible to build of cordwood in your area. I would build within a post and beam frame and work under cover, especially of you will be using one of your dense southern hardwoods. Loblolly pine would be a good choice, if available in your area.

Q: Is Alaska an okay place to build a cordwood house?

A: Alaska is a great place to build a cordwood house and lots of people have already done so. You've certainly got the wood. As with Canada, you will want to go with 24" thick walls, or use Cliff Shockey's double-wall technique. Cliff has a book on the subject. You can contact him at cliffandsylvieATsasktel.net.

Q: My wife and I are planning on building a cordwood home. We've found a plot we like and we plan on putting in a bid. We want to build an earth sheltered home however, the topography of this particular plot will not allow for any southern exposure. If we built into the existing berm, all of our windows would be north-facing. Alternatively, we could decide not to build an earth shelter and simply move the location of the home back, away from the hill, thus allowing for full southern exposure. Which do you think would be more energy efficient: an earth sheltered home (50-60% would be fully sheltered) with northern exposure or a regular home (Frasier frame - 1,200 SQ ft) with full southern exposure? It gets pretty cold up here.

A: That is quite a question, and a good one to ask. It would take a lot of detailed analysis, using heat loss programs, and the like, to accurately answer the question. My guess is that after going through all that, you would not find a significant difference in the energy performance of the two homes. The north-facing earth-shelter is not getting any solar gain, which the above grade cordwood masonry home does. But you begin to heat the earth-shelter from a more favorable starting ambient temperature.     

Sometimes people ask me a question like: Which is better, strawbale or cordwood? I tell them that both techniques can yield good (or bad) houses. I advise them to use indigenous materials and build what they like, and hope that these two considerations are compatible.     

I'm going to give you a similar answer: Build what you like. If one appeals more than the other, go for it. You'll be fine. Or, you can make a list of pros and cons, and tally them all up, assigning weight to the importance or the degree of the "pro" or "con." Then, if you don't like the answer this process leads you to, forget the list and fall back to Plan A: Build what you like.     

Two final comments, which I am sure you have considered, but, just in case.     
(1) The cordwood home sounds like it will have a longer access to get to it. More North Country snow to push, plow or blow.     
(2) Without the southern exposure, the earth-shelter could be a wee bit on the dark side, a bummer at any time of year, but especially in the winter.  

Q: I like the cordwood approach, but wonder if it has ever been used for a retaining wall. My wife and I built our home on a hillside and have a natural rock wall behind the house that we believe needs to be more stable. We have toyed with the idea of building a natural rock retaining wall with the rock from our land, but we know the job will be quite strenuous. The wall is approximately 12' high by 100' long. It would seem that a cord wood wall would make the job much simpler and the wood wouldn't be near as heavy as moving rock. Any advice you can give would be greatly appreciated.

A: Cordwood masonry would not make a good retaining wall. It would be very difficult to prevent constant moisture against the back side of the wall. Fungi would have an ideal climate and, before long, the wood would begin to deteriorate. A few people have built freestanding cordwood walls (not retaining walls). These need to be kept well off the ground and there needs to be some kind of overhanging protective cap at the top of the wall, to stop water running down the wood surface. I would suggest using the stone for your wall. I have built many a fine retaining wall with stones, some of them weighing hundreds of pounds. That's when a good backhoe operator is good to have around.

Q: I live in Gunnison, Colorado where the temperatures can drop to -50 F. They can also hold below -20 for weeks at a time. My question is how well do the cord wood constructed walls stand up to such extreme temperatures. I would imagine that they would insulate pretty well but I thought I would ask someone who would possibly have some first hand experience with sub-zero weather.

A: Cordwood masonry walls hold up very well in the cold. Per capita, they are more popular in Canada than the United States, which says a mouthful. We live in northern New York, near Montreal, with 9000 degree days, the same as Gunnison, Colorado during your heating season of 98-99. (Your 97-98 season was about 10,000 degree days) We heat our 2400 SF (actual usable SF; 2800 SF gross) with 3.5 full cords of hardwood per heating season. That's with 16" white cedar walls. I would think that you would be comfy with 18" to 24" walls of lodgepole pine or quaking aspen where you live.

Q: I would like to know if building a cordwood home [small one] in northern Idaho would be a good idea or should we look at other ways to build?

A: Yes, cordwood masonry works fine in northern Idaho. We have done workshops in that state in both the north (Couer d'Alene) and the south (Idaho City) and the available wood species are very suitable.

Q: Is it possible to make a cordwood home that is on a platform, so that the whole thing could be moved at a later date?

A: Possible? Anything is possible. Would I attempt it? No. Cordwood is strong on compression, not on tension. Moving the building will involve tensile stresses.

Q: I live in the UK, so we have very cold winters going to about -20. I've been looking into both straw bale and cordwood construction. Could you advise me as to which would be the best as there is so much info on both? I'll be building myself but wish to make it as eco as possible.

A: (Kelly) Either cordwood or strawbale would be a good choice in the UK, as there are successful examples of both there. It partly depends on the availability of these materials in your area which might be preferable. They both have very good thermal properties, are natural materials, and the construction process is fairly easy, as far as the walls go. Foundations, roofs and interior finishing are all about the same. I would personally favor cordwood, since there is less risk of problems with moisture potentially getting into the wall and because once the walls are erected there is no further finish or plaster work that must be done, either inside or out.

Q: How well would a cordwood home/cabin do in an environment like the Arizona Mountains? It can get up to 100 in the summer, with very low humidity, and in the winter it can get below freezing, with snow. Is there a specific type of wood you would suggest for this type of dry and hot climate?

A: Cordwood should do well in the climate you describe. In fact, quite a few have been built in similar climates. Lime putty mortar has been iffy in those conditions however, not a high rate of success. I would stick with the Portland based mortar. Use local wood, the less dense the better. Lodgepole pine, quaking aspen and cottonwood have all been successful in the Southwest.


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