Building a sturdy, fuel-efficient house from the wood pile
Fredericton, New Brunswick — Some call it stackwood; others call it pilewood or cordwood. Still others refer to it as log-end construction. But whatever the accepted term, Jack Henstridge thinks of it as something of a lifesaver. It happened this way:
On the very day he learned he had been let go as a company pilot, Mr. Henstridge returned to his home in Upper Gagetown, on the outskirts of this city , to find it a charred ruin. If that weren't bad enough, he discovered that the insurance, taken out many years before, had not kept up with inflated building costs. When the check was finally delivered to him, he had just $8,000 with which to build a new home in the fall of 1973.
That he succeded in building a house of some 2,500 square feet for that low figure results from his stumbling on a building technique that was introduced to North America by early French settlers.
It was widely used in this province and in other parts of Canada some 200 years ago. After Continental troops under Benedict Arnold and Benjamin Franklin had occupied Montreal during the American Revolution, they took it back to New England and upper New York State.
What appealed to Mr. Henstridge about cordwood construction (his preferred term) was the ease of construction.
"If you can pile wood, you can build a cordwood wall," he says. "It's that simple."
Although a "total amateur" when it came to building things, he was confident he had the skill to build a cordwood home -- so he did just that. He also liked the durability of a cordwood structure. Many homes and barns built in Canada with cordwood 200 years ago are still standing.Moreover, in those days only lime was available for the mortar. Today, portland cement is added, resulting in an even more durable structure.
In Decorah, Iowas, the Norwegian-American society museum is housed in a cordwood structure erected in 1855.
Another impressive plus, which Mr. Henstridge discovered later, is good insulating quality of a cordwood wall. To build a cordwood home, he says, is to build an energy-efficient one. It is also attractive, looking very much like a fieldstone structure until viewed from close up.
Size is immaterial, too. From a simple one-room cabin to homes of fortresslike dimensions, cordwood construction is applicable, "because it produces a wall of such remarkable strength," he says.
Very simply, a wall is built by stacking cordwood logs, whole or split, onto a conventional concrete or stone foundation, but with a lime-cement mortar to hold it together permanently. Another way to look at it: Imagine a brick wall with the bricks laid crosswise rather than lengthwise. In this instance, substitute log ends for bricks.
Unlike a brick wall, however, cordwood construction uses mortar somewhat differently -- at each end of the log, rather than down its entire length. So if you were building a wall using 12-inch logs, you might lay them in 4 inches of mortar on the inside and 3 inches on the outside, leaving an air space of 5 inches surrounding the logs in the center of the wall.
Looked at another way, you have two narrow cement mortar walls held together by logs of wood.
The air space in the center of the wall provides insulating value. This, in turn, can be further improved by filling the space with an insulating material -- loose fiber glass, cellulose, ground foam plastic, mineral wool, and the like -- as the wall goes up. After experimenting a little, Jack Henstridge has found that sawdust, mixed with a little lime to help keep it dry, makes a great insulating filler.
As an indication of how effective cordwood construction can be, take the experience of Tom Ryan, who built his cordwood home a few years ago in Greene, Maine, using a wood stove to provide heat.
During one particularly rough winter siege (below-zero temperatures with accompanying high winds), a family emergency forced the Ryans to leave the house suddenly. With no backup oil heat, Mr. Ryan returned four days later, wondering what residual heat, if any, might be left in his home.
Would the water pipes be frozen? To his delight, he found that the indoor temperature had fallen little more than 25 degrees during those three days -- to the 45 degrees F. which the thermometer registered when he first walked in.
A cordwood or log-end wall works this way: The mortar on the inside acts as a heat sink, storing indoor heat for later release when the sun stops shining through the windows or when the wood stove goes out. The air space surrounding the logs in the center of the wall, particularly if filled with an insulating material, prevents that stored heat from being conducted through the wall to the outside.
As wood is a poor conductor of heat, very little is lost directly through the log ends themselves. Moreover, the mortar-wood construction is so tight that there is almost no infiltration of cold air from the outdoors, unless through poorly fitting window and door frames. For the same reasons, the cordwood home is cool in summer.
Mr. Henstridge calculates that a 12-inch-thick wall (using 12-inch-long cordwood, in other words) is adequate for the climate in his part of Canada. A 16-inch-wall would be ideal, he feels. The 2-foot walls that some cordwood builders have chosen is "gilding the lily," in Mr. Henstridge's words. The improved insulation from the extra-thick walls is not worth the cost of the longer logs.
Obviously, good design -- large, sun-gathering windows facing south and small windows facing north -- is important with cordwood construction, just as it is in a conventional wood-frame house.
Besides the efficiency of the cordwood home, there are considerable energy savings in its construction. Because it does not require long straight wooden struts, the wall can be built of waste wood, wood that is otherwise useful only in the fireplace.Bowed trees, split trees, and twisted trees, along with all but the thinnest branches, may be used. Dead trees or trees killed by fire are particularly good, because they are dry.
It is very important to use seasoned barkfree wood in a cordwood wall. Green wood will shrink after use, loosening the logs and allowing for air infiltration through the walls.
On the other hand, if you plan to plaster the walls after construction, such a precaution is not necessary. But true cordwood builders contend that much of the charm of the building is lost if the log ends are covered over.
Because of the speed with which he needed housing after the fire, the Henstridges used green wood. "I had a time-consuming caulking job on my hands a year later," he says.
In this respect, soft woods are better than hardoowds, Mr. Henstridge points out. "Softwood dries faster," he says. He also cautions that bark should be removed from newfelled trees right away, as it comes off "so much more easily" at that stage.
Other pluses for cordwood construction are:
* No heavy lifting -- a child can easily handle such short logs.
* Fire resistance -- the mortar in the wall tends to conduct heat away from any fire that might get started, making it almost impossible for it to spread.
* Soundproof -- the thick walls, plus the fact that log ends tend to absorb noise, make the building unusually quiet.
* Low cost -- cordwood, even at its most expensive, is a whole lot cheaper than conventional timbers that come from a sawmill.
In addition, even the most unskilled person can build a log-end wall.
Malcolm Miller, a Fredericton schoolteacher, built a 3,700-square-foot log-end home, now valued at more than $100,000, for $40,000, because he and his wife and children built all the walls themselves before handing the building over to a contractor for completion.
Are there any disadvantages to cordwood construction? The almost 300 people who have taken Jack Henstridge's advice and gone the cordwood route city only one: It takes longer to construct a wall this way than to erect a conventional stud wall.
Details on cordwood home building are available in the book "Building the Cordwood home," by Jack Henstridge. It costs $7, including postage, and may be ordered from the Cordwood Home, Upper Gagetown, New Brunswick EOG3EO, Canada.