Walter Jeffries wrote:
Victor Johanson wrote:
Walter Jeffries wrote:I would definitely not use poplar for building a cordwood house. Poplar rots very easily. It is a very open, light, airy wood.
I have Cordwood Building: The State of the Art by Rob Roy, wherein poplar is highly recommended as one of the best possible species for building cordwood structures, precisely because it is a "very open, light, airy wood." Proper building technique to avoid decay is essential, however (as it should be with any wood construction).
Aye, I have the book too. There are a lot of things in that book that I find very questionable or outright wrong. Based on my observations of how rapidly poplar rots I would not want to use it. Contact with concrete will speed up the rotting vs simply sitting in a wood pile. Before anyone builds with poplar I would strongly suggest they do a multiyear test to make sure it is going to perform well. A good strategy in general.
I agree that concrete does not cause rot in wood, but I will state after thirty plus years of restoration work, (seeing it most in log cabins where the Cobb/lime chinking was removed and replaced with concrete) that concrete does hold moisture and promote decay, often very rapidly. Cobb and lime plasters can draw moisture out of wood and the atmosphere, while concrete does not "breath" and retains it. I do not promote the use of Portland based chinking, especially in this application.
Concrete does not cause rot in wood.
rob roy wrote:Victor and Walter: Firstly, it is important to know what wood we are talking about when we say poplar. There are tulip poplar, Lombardy poplar and - in the north - quaking aspen is commonly called poplar. In Northern New York, the quaking aspen is called "popple." To be clear, its scientific name is Populus tremuloides. This is the one I say is good for cordwood masonry. Wikipedia says: "Populus tremuloides is a deciduous tree native to cooler areas of North America, one of several species referred to by the common name Aspen. It is commonly called quaking aspen, trembling aspen, American aspen, Quakies, mountain or golden aspen, trembling poplar, white poplar, popple, and even more names. The trees have tall trunks, up to 25 m (82 ft) tall, with smooth pale bark, scarred with black. The glossy green leaves, dull beneath, become golden to yellow, rarely red, in autumn. The species often propagates through its roots to form large groves."
We have been using quaking aspen - which I think is what you are both referring to - as cordwood for over 30 years without a problem. Scores of other builders in Canada and in the US have used it for a long time, as well, including a number of "black and white house" built in Manitoba in the 1930's. Used the way we do in cordwood masonry, showing the end grain on both sides of the wall, the breathability of the poplar is exactly what protects it from rot. I think it was Mac Wells who said "Ventilation is the best preservative we've got." Rot is caused by fungi. If the constant damp conditions necessary to its propagation are not present, the fungi cannot get a foothold. Concrete does not cause rot in wood. Constant damp - and fungi - is what causes rot. Actually, two log-ends touching each other trap moisture far more than a lo-end touching its mortar matrix. I believe the popular (not poplar!) misconception in this regard, expressed by Walter's comment - Contact with concrete will speed up the rotting vs simply sitting in a wood pile - is based upon bad experiences where concrete forming boards, when left in place too long, rot out. They rot out because moisture is trapped between the concrete and the poorly breathing side grain of the forming boards, generally down at ground level.
I like quaking aspen because it has a good R-value. If not seasoned properly in single ranks, covered on the top, but not the sides, the ends can blacken, thus the "black and white" houses. The black is bacteria digesting the wood sugars. After curing, the black can be eradicated with a 30% bleach solution. Problem with that is that the log-ends are also "bleached" of some of their natural cream color. A better solution, I have found, is to clean them with a 4500-rpm circular sander. Makes the ends look very nice indeed. In either case, the black will not return.
Finally, with aspen, I prefer using a variety of different sizes of rounds, as opposed to split log-ends. Here's why: The axe makes a nice clean cut on the side of the log it enters, but, by the time it exits the log, 16" or so later, the split is ragged, not clean. Makes it hard to point the mortar. Hope this helps clarify.