Introduction
Cordwood construction is a sustainable, low-cost method for building shelters, sheds, studios, or homes using stacked softwood logs and natural insulation. This technique offers energy efficiency, local material usage, and unique design possibilities. The walls are built by stacking short logs perpendicular to the frame, creating a solid, insulated structure. This guide will walk you through the process of building a cordwood shelter, from foundation to finishing touches.
Foundation
For a sturdy foundation, consider using an insulated concrete floating slab or a gravel trench foundation to ensure proper drainage. These options provide a solid base for your structure. The insulated concrete floating slab is a poured concrete slab with insulation underneath, which helps prevent moisture from seeping into the foundation. A gravel trench foundation involves digging a trench, filling it with gravel, and pouring a concrete slab on top. Both options are effective in providing a level surface and stability for your cordwood construction.
Structural Frame
The structural frame can be created using simple post-and-beam framing with cedar posts. This requires basic carpentry tools and skills. Measure and cut the posts to the desired height, ensuring they are level and plumb. Use metal brackets or bolts to secure the posts to the foundation. The beams will run horizontally between the posts, providing support for the walls. Ensure the frame is square and secure before proceeding with the wall construction.
Wall Construction
Log Preparation
Remove bark from logs to prevent insect infestation. Logs should be cut to size using a log cutter or saw. Aim for a length of 12 to 16 inches for optimal insulation and structural integrity. The diameter of the logs can vary based on your design preference and local availability.
Log Stacking
Stack the logs with cross-hatching at corners for added strength. Use filler slats to fill any gaps between logs. This technique not only enhances the aesthetic appeal but also improves the structural stability of the walls. Apply mortar mix between each log layer to ensure a tight seal and to add insulation.
Mortar Mixes
Choose from traditional (sand, sawdust, lime, Portland), cob (sand, clay, straw), or papercrete (paper, sand, lime) mixes. These provide structural integrity and insulation. Traditional mortar mix is a blend of sand, sawdust, lime, and Portland cement. Cob mortar is made from sand, clay, and straw, offering a natural and eco-friendly option. Papercrete mortar is a mix of paper, sand, and lime, which is lightweight and easy to work with. Each type of mortar has its advantages and can be chosen based on your specific needs and preferences.
Insulation
Insert insulation between two rows of wood. Options include sawdust or fiberglass. Red cedar is recommended for its natural insulation properties (R-value ~1.25 per inch), decay resistance, and availability. The insulation helps to increase the overall R-value of the wall, making the structure more energy-efficient. For a 16-inch thick wall, the R-value can reach approximately 20, providing excellent thermal performance.
Finishes
No additional finishing work is typically required after the walls are built. The natural appearance of the logs and mortar provides a rustic aesthetic. However, you can apply a clear coat or paint if desired. Ensure any finishes used are compatible with the natural materials to avoid compromising the integrity of the structure.
Summary
Cordwood construction offers a unique and sustainable way to build shelters or homes. By using local materials and traditional techniques, you can create a sturdy, energy-efficient structure that stands the test of time. With careful planning and attention to detail, cordwood construction can be a rewarding and practical approach to building a sustainable shelter.
TLDR: Cordwood construction is a sustainable building method using stacked logs and natural insulation, offering energy efficiency and unique design possibilities. Build a sturdy foundation, prepare and stack logs with mortar mixes, and insert insulation for optimal performance. No additional finishing is typically required.