Kiln Dried vs Air Dried vs Green Standing: Choosing Lumber For a Cabin
There is much debate surrounding which logs to use to build a log cabin, from the species of tree that you choose, to whether you should use dead standing or green logs, kiln or air-dried logs.
Freshly cut trees have high moisture content, and if they are used to build a log cabin immediately, the logs will have a tendency to warp, shrink and twist causing the log cabin to be less structurally sound.
That’s why most people choose to dry their logs out before building a log cabin, which allows them time to stabilize, there are a few different methods of doing this; kiln drying them, air drying them.
The other option is just to use the dead standing as soon as they’ve been harvested.
But which is the best option? This article is going to look through the benefits and negatives of each method to help you decide which log is best for your build.
If you’re still undecided on which logs to use, how many logs you’ll need or how to prepare the logs you can read the following articles before coming back to this one:
- Log Home Logs: All You Need to Know
- The Perils of Lumber Selection for Your Log Cabin
- Harvesting Lumber and Preparing Logs for Your Log Cabin Home
Green logs refer to trees which have been harvested while they’re still alive. Freshly sawn trees usually look and feel wet.
They have high moisture content so need to be dried out before using, with either one of the two methods above.
Some people choose to build with green logs, especially using the butt-and-pass method which uses large pieces of rebar to keep the logs together.
Most people however choose to dry their logs. If you’re going to build a traditional log home using any of the other methods, such as dovetail, saddle notch or corner post – you’re definitely need to dry your logs.
If you build with green logs, they are prone to twisting and shrinking as time goes on which can cause all sorts of problems with windows, door and the structural integrity of the log cabin.
You have two options for drying the logs; letting them air dry over a year, or using a kiln to speed the process up.
We’ll cover the pros and cons of each in the following sections.
Benefits of Green Logs
- This is the quickest way to build a log cabin – no drying process at all.
- Green logs are ideal for the butt-and-pass
- They don’t require any time or energy consuming process to dry them.
Negatives of Green Logs
- They WILL shrink and most likely check as they do so resulting in an unstable home.
- The Butt and Pass method hasn’t been around long enough to ascertain if the log cabins built using green logs are durable and long lasting.
Dead Standing Logs
You may have also heard of dead standing trees.
Dead standing means the trees have died either through aging, infestation, forest fires, fungal diseases or something similar.
The beauty of using dead standing trees is that they have already died so it’s more environmentally friendly and you’re not felling healthy trees and detracting from the forest eco system.
The reason behind why the logs have died will determine whether they are suitable for using to build a log home.
Eron Thomas from Log Cabin Homes uses dead standing trees for most of their cabins, this saves money and time in drying them out:
I can’t emphasize enough how much money can be saved by using dry standing timer, you never have a window that won’t open or a door than won’t close when you use wood that’s already completely dry.
Ideally dead standing trees need to be felled within a couple of years of them dying so the rot doesn’t set in. It’s important to note, the longer the tree has been left standing the more susceptible it is to decay.
Benefits of Dead Standing Logs
- They don’t need to go through a drying process.
- They are ready to use straight away after debarking them.
- They have usually had a couple of years to dry out naturally.
Negatives of Dead Standing Logs
- They could have an insect or fungus infestation.
- They might not be structurally sound.
Air Dried Logs
Most logs have high moisture content when they are felled. They need to reach an equilibrium moisture content of between 10 – 18% – this is the point where they neither gain nor lose moisture and the wood is fully adjusted to the environment.
Air drying the logs allows them to dry out naturally over a long period of time. Logs are usually stacked with spacers in between to allow air to flow between them and dry out.
The length of time that it takes for logs to dry out depends on the species and their age. Harder and older more thick logs take longer to dry out than softer, thinner trees.
Allowing logs to dry out naturally reduces the chance of them cracking or checking.
Some of America’s oldest log homes were built when there wasn’t technology around such as kilns to dry the logs out, so they will have been air dried and they are still standing today.
Benefits of Air Dried Logs
- Logs are dried completely naturally so there will be no internal tensions.
- Retains most of the original color and grains.
- The process isn’t labor intensive.
- Allows the wood to dry more slowly and naturally.
- Keeps the cost of building a log cabin
Negatives of Air Dried Logs
- Takes a long time to dry the logs out.
- If they’re not covered and sealed properly, they could get wet and split.
- The process of air drying takes up more space in comparison to kiln dried logs.
- Pockets of pitch can liquefy if the wood reaches a new high in temperature.
Kiln Dried Logs
Placing logs in a kiln speeds up the process of drying the logs out and allows for a quicker turnaround time.
The logs are placed in a kiln and the temperature is slowly raised to 170OF. The kiln uses fans to circulate the heated air and create a consistent drying rate, forcing the moisture out of the logs. Dehumidifiers are also used to remove the moisture from the air in the kiln.
Kiln dried logs will have a moisture content of between 6 and 10% for a few weeks once they’ve been through the process. However, their moisture content will return to the same equilibrium that air dried logs do.
For example Ponderosa pine has an initial equilibrium moisture content of 8% when it has first been dried, but it will reach between 12 – 19% once it’s absorbed more moisture to reach equilibrium.
There is a widely spread misbelief than kiln drying logs can cause logs to bow and twist. Air dried logs can also do this – it really depends on the quality and the straightness of the log to begin with.
Nor is it true than kiln drying logs prevents them from cracking, this is dependent on the species, the original moisture content and the thickness of the log.
Benefits of Kiln Dried Logs
- The logs are heated to a temperature of 170OF which ensure all fungus, eggs and insects are killed.
- Building a log cabin can take a long time, so this process speeds up the length of the build.
- The resin or pitch in species such as Spruce is dried. Pockets of pitch in logs can liquefy when they reach new temperatures, obviously, the temperature of a built log cabin will never be higher than it is in a kiln.
- Sanitizes the wood without using harsh chemicals
- Creates a durable and long-lasting log which is less likely to shrink or crack.
- Treatments such as staining and wood protection can penetrate the wood deeper because they have a more uniform dryness.
- The process is quick and so reduces the amount of space needed to store logs.
- Logs that are exposed to high temperatures that have problems are easy to spot and can be removed before building the log cabin.
Negatives of Kiln Dried Logs
- Sometimes kiln drying logs can bake internal tensions into the wood.
- Can be more fragile, and chip easily when working the wood with tools.
- It can lose up to 20% of the color and sometimes even some of the grain.
- Wood needs to be kept in a climate-controlled environment after being kiln dried to allow it to reabsorb moisture slowly from the air.
- This is a more expensive process.
This topic always gets a mixed response within the log cabin industry, depending on who you speak to.
Some professional builders argue that air drying logs is the best option whereas other are adamant that kiln dried logs are more stable.
If logs are air dried correctly, and for the right length of time, they will reach the same equilibrium moisture content as kiln dried longs.
While there are plenty of reasons for and against each method, it really does fall down to which method you prefer, your timeframes and budget.
The decision may already be made for you if you’re working within a particular time frame and you need to have the logs dried quickly – in this case you’ll have no other option but to opt for kiln dried logs.
If you’re not in a rush, and you’d like to save some money, then air drying the logs is the best option for you.
Let us know in the comments below which method you’re thinking of using and why, kiln dried logs, air dried logs, or are you just going to use then green or dead standing?