Cordwood Houses - A Green Alternative

Cordwood masonry construction consists of taking uniform lengths of wood and stacking them to form some sort of wall held together by masonry. It's really that simple, but there are lots of variations.

The name "cordwood"comes from the material: uniform lengths of wood like the sort you'd find in a firewood stack, which, of course, is measured in "cords" and hence sometimes called "cordwood". The technique is also called "stackwall"construction or "stovewood" construction.

The pieces of wood are stacked just as you would stack a pile of firewood, except that with each course you lay down two parallel lines of mortar along the outside edges of the stack. The mortar is roughly 4"wide. If you're using 24" long pieces of wood you end up with a space between the mortar, inside the wall space, of about 16". This should be filled with some sort of insulation. You can use fibreglass, rockwool, sawdust or just about anything else that will restrict air flow and heat loss. If you're going off grid and trying to be low impact get creative.

If you're building in a remote area with little manpower remember: getting a 10" thick 15 foot log can be pretty tough. Ropes, planks, pulleys and extra hands can help you accomplish it, but if you've only got one or two people imagine how much easier it is to build the same 15' long wall with 16" pieces.

Before you begin building you need to collect materials. You will need a source of wood rounds, some sort of mortaring materials (cement, lime, sand, sawdust and paper can be used, but other materials will work as well). If you're able to, do yourself a favour and get a small cement mixer. You'll also need some lumber to frame windows and doors, and you'll need some sort of structure for the roof. If you can acquire whatever windows and doors you're going to use, all the better, as you'll be able to frame the rough in holes properly.

The wood should be dry, and de-barked. Remember that cutting, stripping and drying the wood to optimum conditions could be a three year project. Also remember that you can build with green wood if utilitarian shelter is the goal (you can build the cordwood mansion once you're established)

Like all building, you need to start with a foundation. The type of foundation depends on where you're building. Something that's going to be inspected and has to meet a building code will almost certainly require some concrete work, even if only sono-tube piers. A more remote area will allow you more flexibility. In fact, in a very remote area it would be feasible to dig a shallow trench along the perimeter of the building and fill it with rocks a few inches higher than grade level, and then start building the wall on top (the key in this sort of environment is to get past vegetative soil and into mineral soil - sand, gravel or hardpan - which won't deteriorate and move after you've built on it. A rock filled trench will not transfer moisture above the water line.

You could also right on rock, if a large enough space is available, or construct a frame of timbers or logs laid on top of large rocks. Keep an eye on drainage, and remember that you can build a level interior floor afterwards, whether of wood or fill.

Once you have the foundation you can begin building the walls. Walls run from corner to corner, corner to an intersection with another wall, or between two intersections. Corners and intersections are structural opportunities. If you've created a frame of large timbers your structure should be solid before you start filling in the space. If you aren't using a timber frame you'll have to figure out how to tie corners and wall intersections together. It's possible to create interlocking corners, log cabin style, with lengths of wood long enough to be structural but small enough for one person to handle and place.

The walls can consist strictly of log rounds, of split rounds or a combination of the two. Placement of each piece of cordwood can be random or planned, in order to accomplish a tight fit and an eye pleasing design.

Doors and windows start by placing a frame on the wall at the lowest level of the opening, and then stacking and mortaring the cordwood to the side and then over the top of the frame. The frame can be temporary, and removed once the wall has set, or it can be the permanent frame to which the doors and windows get attached.

Thickness of the walls depends on climate. In warm areas thinner walls are acceptable, but the further north you go the thicker you need to make the walls. In some parts of Canada a two wall system (one exterior and one interior) are sometimes used.

The style of roof depends on personal taste, location, the environment and the structure. If snowload is high it makes sense to use a steep roof, if water collection is part of the plan then different materials will be needed, and a large roof are will need a string structure to keep it up. One common characteristic, however, is big overhangs. The less weather touches the walls, the better. Make it a minimum of 16 inches.

Roofing material can be almost anything. There are tin roofed cordwood homes, as well as earthen roofed ones. Again, creativity, strength, safety and low impact are the goals. There are many solutions available.

Cordwood home technology has been around at least 1,000 years, and probably longer. They can be very affordable to build, and can be built by one person if need be. As such, they are an excellent option for someone going off grid.

Rob Chipman maintains two blogs, Bush Pilot Properties, and Off Grid BC, and specializes in remote, fly in, waterfront and off grid properties in the Chilcotin area of British Columbia.

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