Week 74: Part II - Seasoning and Treating Wood

Wood stacked outside the kiln ready for drying

We did a lot of research and determined best practices while using wood. To avoid the common problems with wood, we sourced tree logs that had been lying with the saw mills for a year or two so they were air-dried. We then took this wood and got it kiln dried (or seasoned). In this process, the wood is kept in a kiln for 15 days at controlled temperatures to dry the moisture in the wood. Kiln-dried wood is dried to a moisture level of around 15%.

Wood will always retain some level of moisture, the moisture content is highest when wood is freshly cut and it reduces as wood dries over time. As wood dries, it shrinks and that results in the bending of wood. If the moisture content in atmosphere is high then wood may absorb some of this moisture and expand. Hence, the jammed doors during monsoon. But over time, wood reaches an 'equilibrium moisture content (EMC)'. Once this point is reached then wood does not react noticibly to changes in moisture content. Kiln drying accelerates this drying process. EMC varies with type of wood, local weather conditions, etc. A moisture content between 12-15% is found to be close to EMC in areas of high atmospheric moisture.

Photo of the kiln while it is drying our wood inside

The temperature controls at the kiln

Engineer at kiln checking the moisture content using a moisture meter

Now for wood that is used outdoors there is always the danger of rot. This danger is most prevalent if wood is used close to the ground level where it can potentially be prone to water logging. We have dealt with these problems by avoiding the use of wood for decking on the ground and providing ample slope elsewhere to prevent any water logging.

Then there is the danger of attack by termites and other wood boring insects. This problem is somewhat negated by use of stone/ concrete foundations and plinth, materials that termites cannot pass through. In addition, we have chosen to use primarily teak wood that is known to be naturally resistant to termites. As an additional layer of protection, we are treating all our wood with rot and termite resistant chemical before use in the project.        

Finally, there is the important question of sustainability while using wood. More on that in Part III of this post. Back to Part I with introduction to our choice of using wood.