Many of our customers ask us about kiln drying versus air drying, the advantages of each, and what
we personally recommend here at Rhino Sawmills. 

This article explores this topic in more detail and
we invite you our valued customers to speak to our sawmilling team directly if you have any
questions or need further advice.

Drying timber without the use of a drying kiln, often referred to as air drying or natural drying, is a
cost-effective way to prepare wood as to make it suitable for public sale or for woodworking projects.
Simply put, air drying implies you stack your freshly cut planks in a certain way as to allow natural
movement of air between the individual planks as to promote natural drying and to prevent any wet
spots. Air drying takes longer than kiln drying, but it allows the wood to retain more of its natural
characteristics and can yield excellent results when done correctly.

The major advantage of air drying is the major cost saving from not having to install a drying kiln –
which can be a very expensive depending on the size of the kiln. The more you save money you save
on your production set up, the more you can maximise other parts of your business – such as log
sourcing or getting extra sawmilling machines as to maximise production and income.

The major downside of air drying is the amount of physical space that the drying stacks of timber
take up. Combine this with the duration of drying – which can vary from a few months to a year or
two. As an example a 1-inch / 25mm oak board may take two to three months to air-dry, a 2-inch /
50mm board may take six to eight months, and thicker lumber may take up to a year or more.
This means you will need a lot of space to accommodate the many stacks of drying timber. Air drying
is therefore better suited for smaller sized sawmills which do not have a massive production, or those
who have a lot of space, or those millers who can transport their wet-off-saw timber to a site
dedicated for drying purposes.

If done right with proper management, air drying can be an excellent method of getting higher value
out of your wood compared to wet-off-saw as customers are willing to pay more for properly dried
timber. But remember that air drying requires management to keep track which timbers were cut
when, as well as ensuring that the drying timber is stacked properly to ensure quality drying
throughout.

The success of air drying depends on the specific conditions of your location, so monitoring the
process and adjusting as needed is crucial for achieving the best results. Remember that air drying is
a slow and time-consuming process, but if done right it can yield high-quality timber without the
need for the massive capital and energy required to set up a drying kiln.

Below is a basic guide on how to air dry timber:

1. Choose the Right Timber and Plan Well from the Start.
Start with well-seasoned or green wood that has been freshly cut. Ideally, the wood should have a
moisture content of around 30-50% when you start the drying process. Remember to cut the wood
slightly oversized as the wood will shrink as it dries. This, along with the material that will inevitably
be lost when the boards need to be jointed/planed smooth, mean that green wood should always be
cut larger than the desired finished size. Proper planning from the start will ensure you get the most
value out of your timber with less waste in the end.

2. Prepare the Timber
Consider sealing the ends of each board with a suitable end grain sealer or paint. This prevents
excessive moisture loss from the ends, which can lead to checking or cracking.

3. Create a Stacking Area
Find a well-ventilated and shaded area for stacking your timber. Ensure the space has good natural
airflow as to facilitate the drying process. Stacking your wood with adequate spacing between each
board is crucial – you don’t want any spots that are not exposed to the air.

4. Build Stacks
Create sturdy and level stacks of lumber. Place strips of wood (stickers) between each layer to allow
natural air circulation. Stickers should be evenly spaced and aligned to prevent warping. Ensure that
the stacks are elevated from the ground as to prevent moisture absorption from below. Concrete
blocks or wooden pallets work well for this purpose. Once the stack of wood is stacked and stickered
properly, it’s helpful to add weight to the stack. The lumber at the bottom of the stack is probably
weighed down sufficiently by the wood on top of it, but boards near the top greatly benefit from
added weight.

5. Monitor Moisture Content
Regularly check the moisture content of the wood using a moisture meter. Aim for a moisture
content of around 10-15% as this will be suitable for most application. Depending on your location,
the climate, and the type of wood, drying can take several months to a few years.

6. Protect from the Elements
Shield the stacks from direct sunlight and rain as to avoid rapid drying or moisture absorption. A roof
or tarp can help with this. Ensure proper ventilation by maintaining gaps between the stacked boards
and allow enough space between each stack of drying timber.

7. Patience and Time
Air drying timber is a slow process that requires patience. The drying time depends on various
factors, the most important being wood type, thickness of the boards and your local climate
conditions. Very humid environments will cause the wood to take longer to dry naturally. As a
general rule most hardwoods will take longer to dry than softwoods.

8. Test for Dryness
Once you believe the wood is sufficiently dry, test a few boards by cutting, planing, or measuring
moisture content. If the wood is sufficiently dried then you can sell it ready for woodworking.

9. Final Milling
After air drying, you may consider milling the wood again to achieve the desired dimensions and
smoothness of boards – but this will depend on if you are selling the wood at specific dimensions or
if you’ll be using it yourself for a project.

10. Store Properly
Store your dried timber in a dry, protected area to maintain its moisture content. Properly stacking
and storing wood prevents re-absorption of moisture